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Question

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.

Target Gene/Protein Identity (from UniProt):

• UniProt Accession: Q14644
• Protein Description: RecName: Full=Ras GTPase-activating protein 3; AltName: Full=GAP1(IP4BP); AltName: Full=Ins P4-binding protein;
• Gene Information: Name=RASA3;
• Organism (full): Homo sapiens (Human).
• Protein Family: Not specified in UniProt
• Key Domains: C2_dom. (IPR000008); C2_domain_sf. (IPR035892); PH-like_dom_sf. (IPR011993); PH_domain. (IPR001849); Ras_GTPase. (IPR039360)

MANDATORY VERIFICATION STEPS:

1. Check if the gene symbol "RASA3" matches the protein description above
2. Verify the organism is correct: Homo sapiens (Human).
3. Check if protein family/domains align with what you find in literature
4. If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'RASA3' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information

Research Target:

Please provide a comprehensive research report on the gene RASA3 (gene ID: RASA3, UniProt: Q14644) in human.

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Output

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.

Target Gene/Protein Identity (from UniProt):

• UniProt Accession: Q14644
• Protein Description: RecName: Full=Ras GTPase-activating protein 3; AltName: Full=GAP1(IP4BP); AltName: Full=Ins P4-binding protein;
• Gene Information: Name=RASA3;
• Organism (full): Homo sapiens (Human).
• Protein Family: Not specified in UniProt
• Key Domains: C2_dom. (IPR000008); C2_domain_sf. (IPR035892); PH-like_dom_sf. (IPR011993); PH_domain. (IPR001849); Ras_GTPase. (IPR039360)

MANDATORY VERIFICATION STEPS:

1. Check if the gene symbol "RASA3" matches the protein description above
2. Verify the organism is correct: Homo sapiens (Human).
3. Check if protein family/domains align with what you find in literature
4. If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'RASA3' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information

Research Target:

Please provide a comprehensive research report on the gene RASA3 (gene ID: RASA3, UniProt: Q14644) in human.

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Plan and identity verification
- Target verified: Human RASA3 (UniProt Q14644), also known as GAP1(IP4BP)/GAP1IP4BP, a Ras-GTPase–activating protein family member with C2, central RasGAP-related catalytic domain, and a PH domain. Contemporary platelet literature describes these domains and their roles in membrane binding and regulation, confirming concordance with the UniProt domain annotations (C2, RasGAP-related, PH) and the human organism context (Homo sapiens) (odonoghue2024rolesofg pages 18-19, odonoghue2024rolesofg pages 10-11). URL: https://doi.org/10.1042/BSR20231420 (May 2024).

Comprehensive research report on RASA3 (human; UniProt Q14644)

1) Key concepts and definitions with current understanding
- Molecular identity and domains: RASA3 is a small GTPase–activating protein (GAP) in the RasGAP family that inactivates small GTPases by accelerating GTP hydrolysis. In human platelets and megakaryocytes, RASA3 contains an N‑terminal C2 domain, a central RasGAP-related catalytic domain, and a C‑terminal PH domain. The C2 and PH domains contribute to membrane association and are integral to regulation of its GAP activity at the plasma membrane (odonoghue2024rolesofg pages 18-19, odonoghue2024rolesofg pages 10-11). URL: https://doi.org/10.1042/BSR20231420 (May 2024).
- Enzymatic reaction and substrate specificity: RASA3 functions as a dual-specificity GAP that prominently targets Rap1 and also exhibits activity toward Ras (reported as H‑Ras in platelet-oriented sources). In platelets, RASA3 reduces Rap1‑GTP to restrain integrin activation; genetic and biochemical evidence place RAP1 as the primary physiological substrate in this lineage (stefanini2015rasa3isa pages 1-2, odonoghue2024rolesofg pages 10-11). URLs: https://doi.org/10.1172/jci77993 (Apr 2015); https://doi.org/10.1042/BSR20231420 (May 2024).
- Subcellular localization and membrane targeting: In platelets, RASA3 is functionally linked to the plasma membrane via its lipid-binding PH domain. P2Y12–Gi–PI3K signaling generates PI(3,4,5)P3 that promotes RASA3 membrane association; in this context, RASA3 is proposed to become functionally inhibited to allow sustained Rap1‑GTP during platelet activation. Proteomic evidence identifies RASA3 as a PI(3,4,5)P3‑binding protein. Some studies observed context-dependent membrane association that is not uniformly PI3K-sensitive, indicating cell state–dependent regulation (odonoghue2024rolesofg pages 18-19, stefanini2015rasa3isa pages 8-9). URLs: https://doi.org/10.1042/BSR20231420 (May 2024); https://doi.org/10.1172/jci77993 (Apr 2015).

2) Recent developments and latest research (prioritize 2023–2024)
- 2024 platelet GAPs review: A curated synthesis of G proteins and GAPs in platelets details RASA3’s roles, lipid regulation, and quantitative proteomics. It reports human platelet abundance (~8,293 copies/platelet) and curated phosphosite counts (~12), and reiterates RASA3 specificity for Rap1 (with reported H‑Ras activity), its inhibitory role on platelet adhesion/aggregation, and its linkage to P2Y12→PI3K→PIP3 pathways (odonoghue2024rolesofg pages 10-11). URL: https://doi.org/10.1042/BSR20231420 (May 2024).
- 2023 T‑cell trafficking: Genetic deletion of Rasa3 together with Sipa1 in mouse T cells caused spontaneous Rap1 activation and excessive adhesion, leading to sequestration in lung capillaries; blockade of LFA‑1 or deletion of talin1 or Rap1 rescued the phenotype. Lymph node entry and motility remained intact, but egress was delayed, implicating Rasa3‑mediated Rap1 inactivation as critical for proper lymphocyte recirculation. These findings update RASA3’s physiological scope in hematopoietic trafficking beyond platelets (horitani2023thecriticalrole pages 1-2). URL: https://doi.org/10.3389/fimmu.2023.1234747 (Jul 2023).
- 2024 synthesis of platelet mechanisms: The same 2024 review consolidates earlier mechanistic observations that ADP–P2Y12 activation drives PI3K-dependent modulation of RASA3 to sustain Rap1 activity during platelet activation; it also notes conflicting observations on membrane localization control, highlighting active debate on context-specific regulation (odonoghue2024rolesofg pages 18-19). URL: https://doi.org/10.1042/BSR20231420 (May 2024).

3) Current applications and real-world implementations
- Antiplatelet therapy mechanism context: The platelet model positions RASA3 as a key negative regulator of CalDAG‑GEFI→Rap1 signaling. P2Y12 antagonists (a clinical antiplatelet class) would be expected to maintain RASA3 activity and thereby destabilize thrombus growth by promoting Rap1‑GTP turnover. Experimental mouse work supports that P2Y12 inhibition prevents the inactivation of RASA3, which contributes mechanistically to thrombus destabilization under antiplatelet therapy (stefanini2015rasa3isa pages 8-9). URL: https://doi.org/10.1172/jci77993 (Apr 2015).
- Quantitative proteomics for target assessment: Human platelet proteomic copy-number estimates and phosphosite annotations for RASA3 provide a quantitative framework for systems pharmacology and signaling models of platelet activation/inhibition (odonoghue2024rolesofg pages 10-11). URL: https://doi.org/10.1042/BSR20231420 (May 2024).

4) Expert opinions and analysis from authoritative sources
- Consensus model in platelets: Expert synthesis in 2024 concludes that RASA3 is a central Rap1/Ras GAP in platelets, that it restrains platelet adhesion and aggregation by reducing Rap1‑GTP, and that it is regulated by phosphoinositide signaling downstream of P2Y12–Gi–PI3K. The review also flags experimental inconsistencies in membrane targeting, suggesting regulation is context-dependent and may vary with experimental systems (odonoghue2024rolesofg pages 18-19, odonoghue2024rolesofg pages 10-11). URL: https://doi.org/10.1042/BSR20231420 (May 2024).
- Genetic causality for hematologic phenotypes: The JCI study established RASA3 as a critical inhibitor of Rap1-dependent platelet activation in vivo. Rasa3 loss or reduction led to hyperresponsive platelets, constitutive integrin activation, shortened platelet lifespan with increased turnover, and thrombocytopenia; removal of the upstream Rap1 GEF (CalDAG‑GEFI) normalized Rap1 signaling and platelet counts, demonstrating a causal RASA3→Rap1 axis in platelet homeostasis (stefanini2015rasa3isa pages 1-2, stefanini2015rasa3isa pages 8-9). URL: https://doi.org/10.1172/jci77993 (Apr 2015).
- Immunocyte trafficking: 2023 mechanistic genetics in T cells show that Rasa3-mediated Rap1 inactivation is essential to prevent pathological adhesion during microvascular transit and to ensure efficient egress from lymph nodes, refining our understanding of RASA3’s role in integrin-dependent leukocyte trafficking (horitani2023thecriticalrole pages 1-2). URL: https://doi.org/10.3389/fimmu.2023.1234747 (Jul 2023).

5) Relevant statistics and data from recent studies
- Protein copy number and PTMs in human platelets: RASA3 ≈ 8,293 copies per platelet; ~12 phosphosites curated in the platelet proteome table (Bioscience Reports 2024) (odonoghue2024rolesofg pages 10-11). URL: https://doi.org/10.1042/BSR20231420 (May 2024).
- Functional positioning among platelet GAPs: The 2024 review highlights RASA3 as abundant among platelet GAPs and functionally assigned to Rap1/H‑Ras regulation with direct consequences for αIIbβ3 integrin activation and platelet aggregation (odonoghue2024rolesofg pages 10-11). URL: https://doi.org/10.1042/BSR20231420 (May 2024).
- In vivo hematologic phenotypes (mouse): Rasa3 reduction or loss causes marked thrombocytopenia due to accelerated platelet clearance and shortened lifespan; CalDAG‑GEFI deletion abrogates basal Rap1 activation and rescues counts, quantitatively linking RASA3 activity to platelet homeostasis in vivo (stefanini2015rasa3isa pages 1-2, stefanini2015rasa3isa pages 8-9). URL: https://doi.org/10.1172/jci77993 (Apr 2015).

Mechanistic pathway integration
- Core pathway: In resting platelets, RASA3 counters the CalDAG‑GEFI→Rap1 pathway to maintain low Rap1‑GTP, thereby keeping talin-dependent αIIbβ3 integrin in an inactive state. Upon activation, ADP acting via P2Y12–Gi engages PI3K to produce PI(3,4,5)P3; RASA3 is recruited to the membrane and becomes functionally inhibited, limiting Rap1‑GTP turnover and enabling sustained integrin activation and platelet aggregation. This process is reversible or blunted when P2Y12 or PI3K are inhibited, an effect that in part reflects preserved RASA3 activity (stefanini2015rasa3isa pages 1-2, stefanini2015rasa3isa pages 8-9, odonoghue2024rolesofg pages 18-19). URLs: https://doi.org/10.1172/jci77993 (Apr 2015); https://doi.org/10.1042/BSR20231420 (May 2024).
- Broader hematopoietic trafficking: In T cells, Rasa3 (with Sipa1) tempers Rap1-driven integrin adhesion during pulmonary capillary transit and is required for lymph node egress; loss results in excessive adhesion and trafficking defects without impairing chemokine responsiveness, emphasizing precise spatiotemporal GAP control of Rap1 (horitani2023thecriticalrole pages 1-2). URL: https://doi.org/10.3389/fimmu.2023.1234747 (Jul 2023).

Physiological roles and tissue contexts
- Platelets and megakaryocytes: RASA3 is highly expressed in human platelets, acts as the key Rap1 GAP to maintain quiescence, and prevents premature integrin activation and aggregation. Mouse genetics show that Rasa3 deficiency yields hyperactive platelets, thrombocytopenia, and bleeding phenotypes; these effects map to the Rap1–talin–αIIbβ3 axis (stefanini2015rasa3isa pages 1-2, odonoghue2024rolesofg pages 17-18, odonoghue2024rolesofg pages 10-11). URLs: https://doi.org/10.1172/jci77993 (Apr 2015); https://doi.org/10.1042/BSR20231420 (May 2024).
- Erythropoiesis/megakaryopoiesis (inference from genetics): Mouse studies cited by recent immunology work and platelet literature associate Rasa3 loss with anemia and thrombocytopenia, indicating roles in erythroid and megakaryocytic lineages mediated through Rap1 signaling; these data support but do not by themselves delineate all steps in human erythropoiesis (horitani2023thecriticalrole pages 1-2, stefanini2015rasa3isa pages 1-2). URLs: https://doi.org/10.3389/fimmu.2023.1234747 (Jul 2023); https://doi.org/10.1172/jci77993 (Apr 2015).
- Lymphocyte trafficking: Rasa3 is necessary to terminate Rap1 signaling to avoid pathological adhesion in lung microvasculature and to enable timely egress from lymph nodes, underscoring its role in integrin-dependent immune cell trafficking (horitani2023thecriticalrole pages 1-2). URL: https://doi.org/10.3389/fimmu.2023.1234747 (Jul 2023).
- Endothelium: Direct endothelial cell-autonomous roles are not resolved by the gathered sources; platelet–endothelial interactions are indirectly implicated through integrin activation and vascular hemostasis mechanisms (odonoghue2024rolesofg pages 10-11). URL: https://doi.org/10.1042/BSR20231420 (May 2024).

Human genetics and disease associations
- Established in vivo causality (mouse): Naturally occurring and engineered Rasa3 variants produce severe thrombocytopenia and anemia with accelerated platelet turnover; platelet phenotypes are tightly linked to Rap1 deregulation and integrin αIIbβ3 activation (stefanini2015rasa3isa pages 1-2). URL: https://doi.org/10.1172/jci77993 (Apr 2015).
- Human variant evidence: The gathered 2023–2024 sources reviewed here do not provide definitive human pathogenic variant evidence for RASA3; disease relevance is primarily supported by mechanistic homology and strong mouse genetics. Thus, clinical translation remains inferential in these specific sources (odonoghue2024rolesofg pages 10-11, horitani2023thecriticalrole pages 1-2). URLs: https://doi.org/10.1042/BSR20231420 (May 2024); https://doi.org/10.3389/fimmu.2023.1234747 (Jul 2023).

Translational implications
- Antiplatelet pharmacology: The RASA3-centered model rationalizes how P2Y12 antagonists (standard-of-care antiplatelets) may preserve RASA3 activity and diminish sustained Rap1 signaling, providing a mechanistic underpinning for thrombus instability under therapy (stefanini2015rasa3isa pages 8-9). URL: https://doi.org/10.1172/jci77993 (Apr 2015).
- Biomarker and systems modeling: Quantitative copy numbers and phosphosite annotations facilitate modeling of platelet activation networks and may assist in identifying states of heightened thrombotic or bleeding risk associated with altered RASA3 signaling (odonoghue2024rolesofg pages 10-11). URL: https://doi.org/10.1042/BSR20231420 (May 2024).

Concise evidence summary
| Category | Key finding | Mechanistic/experimental evidence | Year & Source (journal) | URL | Citation IDs |
|---|---|---|---:|---|---|
| Identity & domains | Human RASA3 (GAP1/IP4BP) contains N-terminal C2 domain, central Ras-GAP (RasGRD) domain, and C-terminal PH domain; C2/PH implicated in membrane binding and regulation of GAP activity. | Domain roles and membrane-binding properties described in platelet-focused review (C2/PH required for membrane interaction). | 2024, Bioscience Reports | https://doi.org/10.1042/BSR20231420 | (odonoghue2024rolesofg pages 18-19) |
| Enzymatic function & substrate specificity | Acts as a GTPase-activating protein (GAP) with activity against Rap1 (primary) and reported activity toward Ras/H‑Ras (dual specificity reported). | Mouse genetic and biochemical data showing RASA3 reduces Rap1-GTP levels in platelets; review notes Rap1 and H‑Ras specificity. | 2015, J Clin Invest; 2024, Bioscience Reports | https://doi.org/10.1172/jci77993 ; https://doi.org/10.1042/BSR20231420 | (stefanini2015rasa3isa pages 1-2, odonoghue2024rolesofg pages 18-19) |
| Regulators & membrane targeting | Regulated by Gi-coupled P2Y12 → PI3K signaling: PI3K-generated PIP3 recruits/inactivates RASA3 via PH domain; PH domain reported to bind PIP2/PIP3; some context-dependent differences reported for PM association. | Platelet experiments and reviews linking P2Y12/PI3K to RASA3 membrane recruitment and functional inactivation; PI3K inhibitors alter RASA3 regulation (with some conflicting observations). | 2015, J Clin Invest; 2024, Bioscience Reports | https://doi.org/10.1172/jci77993 ; https://doi.org/10.1042/BSR20231420 | (stefanini2015rasa3isa pages 8-9, odonoghue2024rolesofg pages 18-19) |
| Core signaling pathway roles | RASA3 restrains Rap1 → talin → αIIbβ3 integrin inside-out activation in platelets; loss of RASA3 → elevated Rap1-GTP and constitutive integrin activation leading to premature platelet adhesion/aggregation. | Mouse knockout/mutant platelet phenotypes, biochemical Rap1-GTP measurements, and rescue experiments (CalDAG‑GEFI deletion reverses thrombocytopenia) demonstrating RASA3 as critical RAP-GAP in platelet signaling. | 2015, J Clin Invest; 2024, Bioscience Reports | https://doi.org/10.1172/jci77993 ; https://doi.org/10.1042/BSR20231420 | (stefanini2015rasa3isa pages 1-2, odonoghue2024rolesofg pages 17-18) |
| Physiological roles | Essential for platelet quiescence/homeostasis; implicated in erythropoiesis/megakaryopoiesis (mouse mutants show anemia/thrombocytopenia); regulates lymphocyte trafficking (T cell pulmonary transit and lymph node egress via Rap1 inactivation). | Mouse genetic models (Rasa3 mutants, tissue-specific deletions), T-cell conditional double knockout with Sipa1 showing Rap1 hyperactivation, lung sequestration and egress defects. | 2015, J Clin Invest; 2023, Frontiers in Immunology | https://doi.org/10.1172/jci77993 ; https://doi.org/10.3389/fimmu.2023.1234747 | (stefanini2015rasa3isa pages 1-2, horitani2023thecriticalrole pages 1-2) |
| Recent 2023–2024 updates | 2023: Rasa3 (with Sipa1) identified as critical Rap1-GAPs in T cells controlling pulmonary transit and egress; 2024: platelet-focused reviews consolidate RASA3 regulation by P2Y12/PI3K and report proteomic annotations (binding partners, phosphosites). | Horitani et al. (2023) T‑cell genetic studies; 2024 review summarizes platelet proteomics, lipid binding, and functional context. | 2023, Frontiers in Immunology; 2024, Bioscience Reports | https://doi.org/10.3389/fimmu.2023.1234747 ; https://doi.org/10.1042/BSR20231420 | (horitani2023thecriticalrole pages 1-2, odonoghue2024rolesofg pages 10-11) |
| Quantitative data | RASA3 abundance in human platelets reported ≈ 8,293 copies/platelet; table entry reports ~12 phosphorylation sites annotated. | Proteomics/curated platelet protein table in 2024 review. | 2024, Bioscience Reports | https://doi.org/10.1042/BSR20231420 | (odonoghue2024rolesofg pages 10-11) |
| Human genetics / disease associations | Mouse Rasa3 missense alleles (e.g., G125V, "scat") cause severe thrombocytopenia and anemia; mouse/chimera data link RASA3 loss to hematopoietic defects; direct human pathogenic variants not established in these sources. | Experimental mouse genetics (mutants, chimeras) demonstrating causal phenotypes; human disease relevance inferred but not directly proven in these cited works. | 2015, J Clin Invest; 2023, Frontiers in Immunology | https://doi.org/10.1172/jci77993 ; https://doi.org/10.3389/fimmu.2023.1234747 | (stefanini2015rasa3isa pages 1-2, horitani2023thecriticalrole pages 1-2) |

Table: Concise, evidence-linked summary of molecular features, regulation, pathways, physiological roles, recent updates, quantitative data, and genetic insights for human RASA3 (UniProt Q14644), with primary citations to the gathered literature.

Notes on limitations and open questions
- While platelet and T‑cell data are strong, comprehensive definition of RASA3 regulation across diverse human tissues (including endothelium) and systematic human genetic association studies were not captured in the gathered 2023–2024 literature excerpts. Some regulatory aspects (e.g., precise PI3K dependence of membrane association) appear context-dependent and merit further investigation (odonoghue2024rolesofg pages 18-19). URL: https://doi.org/10.1042/BSR20231420 (May 2024).

References (URLs and dates embedded above)

References

1. (odonoghue2024rolesofg pages 18-19): Lorna O'Donoghue and Albert Smolenski. Roles of g proteins and their gtpase-activating proteins in platelets. Bioscience Reports, May 2024. URL: https://doi.org/10.1042/bsr20231420, doi:10.1042/bsr20231420. This article has 6 citations and is from a peer-reviewed journal.

2. (odonoghue2024rolesofg pages 10-11): Lorna O'Donoghue and Albert Smolenski. Roles of g proteins and their gtpase-activating proteins in platelets. Bioscience Reports, May 2024. URL: https://doi.org/10.1042/bsr20231420, doi:10.1042/bsr20231420. This article has 6 citations and is from a peer-reviewed journal.

3. (stefanini2015rasa3isa pages 1-2): Lucia Stefanini, David S. Paul, Raymond F. Robledo, E. Ricky Chan, Todd M. Getz, Robert A. Campbell, Daniel O. Kechele, Caterina Casari, Raymond Piatt, Kathleen M. Caron, Nigel Mackman, Andrew S. Weyrich, Matthew C. Parrott, Yacine Boulaftali, Mark D. Adams, Luanne L. Peters, and Wolfgang Bergmeier. Rasa3 is a critical inhibitor of rap1-dependent platelet activation. The Journal of clinical investigation, 125 4:1419-32, Apr 2015. URL: https://doi.org/10.1172/jci77993, doi:10.1172/jci77993. This article has 167 citations.

4. (stefanini2015rasa3isa pages 8-9): Lucia Stefanini, David S. Paul, Raymond F. Robledo, E. Ricky Chan, Todd M. Getz, Robert A. Campbell, Daniel O. Kechele, Caterina Casari, Raymond Piatt, Kathleen M. Caron, Nigel Mackman, Andrew S. Weyrich, Matthew C. Parrott, Yacine Boulaftali, Mark D. Adams, Luanne L. Peters, and Wolfgang Bergmeier. Rasa3 is a critical inhibitor of rap1-dependent platelet activation. The Journal of clinical investigation, 125 4:1419-32, Apr 2015. URL: https://doi.org/10.1172/jci77993, doi:10.1172/jci77993. This article has 167 citations.

5. (horitani2023thecriticalrole pages 1-2): Shunsuke Horitani, Yoshihiro Ueda, Yuji Kamioka, Naoyuki Kondo, Yoshiki Ikeda, Makoto Naganuma, and Tatsuo Kinashi. The critical role of rap1-gaps rasa3 and sipa1 in t cells for pulmonary transit and egress from the lymph nodes. Frontiers in Immunology, Jul 2023. URL: https://doi.org/10.3389/fimmu.2023.1234747, doi:10.3389/fimmu.2023.1234747. This article has 4 citations and is from a peer-reviewed journal.

6. (odonoghue2024rolesofg pages 17-18): Lorna O'Donoghue and Albert Smolenski. Roles of g proteins and their gtpase-activating proteins in platelets. Bioscience Reports, May 2024. URL: https://doi.org/10.1042/bsr20231420, doi:10.1042/bsr20231420. This article has 6 citations and is from a peer-reviewed journal.

Citations

1. odonoghue2024rolesofg pages 10-11
2. horitani2023thecriticalrole pages 1-2
3. odonoghue2024rolesofg pages 18-19
4. odonoghue2024rolesofg pages 17-18
5. https://doi.org/10.1042/BSR20231420
6. https://doi.org/10.1172/jci77993
7. https://doi.org/10.3389/fimmu.2023.1234747
8. https://doi.org/10.1042/bsr20231420,
9. https://doi.org/10.1172/jci77993,
10. https://doi.org/10.3389/fimmu.2023.1234747,

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Question

Gene Research for Functional Annotation

Please provide a comprehensive research report on the gene RASA3 (Q14644) in human.

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

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Output

RASA3 (Q14644) – Function, Regulation, and Biological Role in Human Cells

Gene and Protein Overview

RASA3 (Ras p21 protein activator 3) is a human gene encoding a Ras GTPase-activating protein (RasGAP) of the GAP1 family (pubmed.ncbi.nlm.nih.gov). It is also known by synonyms GAP1(IP4BP) (GTPase-activating protein 1, inositol 1,3,4,5-tetrakisphosphate-binding protein) and R-Ras GAP (pubmed.ncbi.nlm.nih.gov). The UniProt identifier for the human RASA3 protein is Q14644. RASA3 was first identified in 1995 as a protein isolated from platelet membranes due to its high-affinity binding to inositol 1,3,4,5-tetrakisphosphate (IP₄) (pubmed.ncbi.nlm.nih.gov). This discovery established RASA3 as the first known receptor for IP₄ and hinted at its regulatory role in signal transduction. At the sequence and structural level, RASA3 belongs to the GAP1 subfamily of RasGAPs, which is characterized by multiple conserved domains: two N-terminal C2 domains (calcium-dependent phospholipid-binding domains), a central pleckstrin homology (PH) domain, and a C-terminal RasGAP catalytic domain (pmc.ncbi.nlm.nih.gov). The tandem C2 domains can bind Ca²⁺ and phospholipids, while the PH domain (sometimes termed a PH-BTK domain) can bind membrane phosphoinositides and signaling lipids (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). These domains target RASA3 to cellular membranes and contribute to its regulation by lipid second messengers.

Molecular Function and Mechanism of RASA3

RASA3’s primary function is as a GTPase-activating protein for Ras-related small GTPases, meaning it accelerates the hydrolysis of GTP bound to these signaling proteins, thereby switching them from an active (GTP-bound) to inactive (GDP-bound) state. Biochemically, RASA3 is bifunctional in its substrate specificity: it can act on Ras family GTPases (e.g. H-Ras, N-Ras, K-Ras, and R-Ras) as well as on the Ras-related protein Rap1 (pubmed.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). In vitro assays have demonstrated that RASA3’s GAP domain stimulates GTP hydrolysis on both Ras and Rap1, distinguishing it from some other RasGAPs that act only on Ras. A 2006 biochemical study by Kupzig et al. showed that all members of the GAP1 family (including RASA3) can function as GAPs for both Ras and Rap1, confirming RASA3’s dual specificity (pmc.ncbi.nlm.nih.gov). The catalytic mechanism of RASA3’s GAP domain follows the canonical RasGAP paradigm: it provides an “arginine finger” residue into the GTPase’s active site to stabilize the transition state of GTP hydrolysis (pmc.ncbi.nlm.nih.gov). Notably, Rap1 is normally resistant to Ras-specific GAPs due to differences in its active site, but RASA3 uses the same arginine-finger mechanism to inactivate Rap1, rather than the “asparagine thumb” mechanism employed by dedicated Rap1GAPs (pmc.ncbi.nlm.nih.gov). This indicates that RASA3’s GAP domain is structurally equipped to accommodate both Ras and Rap1, underscoring its role as a broad regulator of Ras superfamily signaling. In summary, the enzymatic reaction catalyzed by RASA3 is: Ras-GTP → Ras-GDP + P_i (with RASA3 greatly accelerating the release of inorganic phosphate), and similarly for Rap1-GTP. By stimulating GTP hydrolysis, RASA3 turns off Ras/Rap1 signaling pathways, acting as a critical negative regulator in cellular signal transduction (pmc.ncbi.nlm.nih.gov).

Domain Structure and Regulation by Lipids

The multidomain architecture of RASA3 (C2-C2-PH-GAP) is intimately linked to its regulation and localization. The C2 domains (at the N-terminus) are Ca²⁺-binding modules often found in signaling proteins that transiently associate with membranes. In RASA3, the two C2 domains likely cooperate to recruit or anchor the protein to intracellular membranes (such as the inner leaflet of the plasma membrane) in response to calcium influx (pmc.ncbi.nlm.nih.gov). The PH domain of RASA3 binds to specific phosphoinositides and inositol phosphates, which modulate RASA3’s activity and subcellular localization. Quantitative binding studies and proteomic screens have shown that the RASA3 PH domain has high affinity for the tris-phosphorylated phosphoinositide PI(3,4,5)P₃ (PIP₃) (pmc.ncbi.nlm.nih.gov), as well as notable binding to PI(4,5)P₂ (a membrane lipid) and soluble inositol 1,3,4,5-tetrakisphosphate (IP₄) (pmc.ncbi.nlm.nih.gov). In fact, RASA3’s original designation GAP1(IP4BP) reflects its ability to bind IP₄ with nanomolar affinity (pubmed.ncbi.nlm.nih.gov). These interactions suggest a regulatory mechanism wherein second messengers control RASA3: for example, PIP₃ produced by PI3-kinase and IP₄ produced downstream of PLCγ can bind RASA3’s PH domain and alter its activity or localization.

Crucially, recent studies indicate that PIP₃ binding inhibits RASA3’s GAP activity, providing a feedback link between PI3K signaling and Ras/Rap regulation. In T lymphocytes, it was observed that activating PI3K (which raises PIP₃ levels at the membrane) functionally inactivates RASA3, thereby relieving its restraining effect on Rap1 (pmc.ncbi.nlm.nih.gov). In contrast, when PI3K is blocked pharmacologically, T-cell receptor stimulation fails to activate Rap1 unless RASA3 is missing, implying that PIP₃ generation is normally required to suppress RASA3 and allow Rap1 activation (pmc.ncbi.nlm.nih.gov). Consistently, a mutant RASA3 PH domain that cannot bind PIP₃ was shown to render RASA3 constitutively active as a GAP; overexpression of this PH-mutant RASA3 more strongly suppressed integrin activation than wild-type RASA3, underscoring that PH domain binding to lipid inhibits RASA3’s function (pmc.ncbi.nlm.nih.gov). Together, these findings support a model in which RASA3 is kept active under resting conditions (when PIP₃ is low) to police basal Ras/Rap activity, but upon receptor stimulation (and PI3K activation), PIP₃ binding to RASA3’s PH domain releases the brake on Ras/Rap signaling. The role of soluble IP₄ in RASA3 regulation is less completely understood, but as an IP₃ metabolite, IP₄ may compete with phosphoinositides for the PH domain or promote a conformational state of RASA3. Early biochemical studies suggested IP₄ binding could sequester RASA3 or modulate its localization (pubmed.ncbi.nlm.nih.gov), though the in vivo consequence remains an area of investigation. In summary, RASA3’s activity is tightly regulated by lipid messengers: it contains built-in lipid-sensing domains (C2 and PH) that control when and where it inactivates Ras and Rap1.

Subcellular Localization

RASA3 is predominantly a cytosolic protein with regulated membrane association. It lacks any transmembrane region, instead associating with membranes via its C2 and PH domains. Functional studies have shown that RASA3 must localize to the inner surface of the plasma membrane to access its GTPase substrates (which themselves are membrane-attached). For instance, the spontaneous mouse mutant “scat” (severe combined anemia and thrombocytopenia) carries a single G125V substitution in the Rasa3 protein that disrupts its membrane targeting (pmc.ncbi.nlm.nih.gov). This mutation causes RASA3 to mislocalize to the cytosol in erythroid cells, rendering it unable to inactivate membrane-bound Ras (pmc.ncbi.nlm.nih.gov). As a result, Ras-GTP levels in scat red blood cells are abnormally high due to the absence of RASA3 at the membrane (pmc.ncbi.nlm.nih.gov). This provides compelling evidence that correct subcellular localization (membrane recruitment) is essential for RASA3’s function. Under normal circumstances, RASA3 is thought to cycle between the cytosol and the plasma membrane. When cytosolic Ca²⁺ rises or specific lipids are present, RASA3’s C2 and PH domains cooperate to recruit it to the membrane, where it can bind and deactivate Ras or Rap1. Conversely, signals like PIP₃ binding may alter its localization or conformation, possibly keeping it from the membrane (or in an inhibited membrane-bound state) during active signaling. In platelets and leukocytes, RASA3 is found in the cytosolic fraction at rest but rapidly relocalizes upon activation of upstream signals (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Overall, RASA3 operates at the cytosol–membrane interface, carrying out its GAP function on the inner leaflet of the plasma membrane (and potentially endomembranes) where Ras/Rap1 signaling occurs.

Biological Processes and Pathways Involving RASA3

Negative Regulator of Ras–MAPK Signaling

As a RasGAP, RASA3 is an important negative regulator of the Ras–RAF–MEK–ERK (MAPK) cascade. By accelerating Ras-GTP turnover, RASA3 dampens Ras-dependent signaling for cell proliferation and differentiation. This role is especially critical in hematopoietic cells. Erythropoiesis (red blood cell development) provides a clear example: RASA3 is required to keep Ras activity in check during red cell maturation. In the scat mouse model, loss of functional RASA3 led to excessive Ras-GTP in erythroid cells and a block in erythropoiesis, causing severe anemia (pmc.ncbi.nlm.nih.gov). Approximately 94% of scat mutant mice die in early infancy (by ~30 days of age) during acute “crisis” episodes of bone marrow failure (pmc.ncbi.nlm.nih.gov). These crises are attributed to unchecked Ras signaling disrupting the normal feedback control of blood cell production (pmc.ncbi.nlm.nih.gov). The crucial involvement of RASA3 in the Ras/MAPK pathway is further supported by human data: biallelic loss-of-function mutation in RASA3 has been identified in a child with a Rasopathy-like syndrome, featuring developmental abnormalities and bone marrow failure (pmc.ncbi.nlm.nih.gov). Rasopathies (such as Noonan, LEOPARD, or Costello syndromes) are typically caused by hyperactive Ras/MAPK signaling, and the patient with mutant RASA3 showed overlapping clinical features (growth delays, distinctive facial features, and cytopenias) (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). The RASA3 variant (K385T) in this case affects the conserved RasGAP domain, and was predicted to abolish RASA3’s activity (pmc.ncbi.nlm.nih.gov). Together with the mouse models, this suggests that RASA3 normally acts as a tumor suppressor-like brake on Ras in cells: when RASA3 function is lost, Ras-MAPK signaling becomes overactive, leading to disordered proliferation or differentiation (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Indeed, RASA3’s protein interaction network in human cells is enriched for Ras/MAPK pathway members and known Rasopathy genes (pmc.ncbi.nlm.nih.gov), consistent with its placement in this signaling pathway. While RASA3 is not redundant with other RasGAPs (e.g. RASA1 or NF1) in certain contexts (pmc.ncbi.nlm.nih.gov), it may have specialized importance in blood lineages and perhaps other cell types where its expression is high. RASA3 has been reported as expressed in hematopoietic progenitors and various tissues, and its dysregulation could contribute to oncogenic processes in leukemia or other cancers through relief of Ras signaling constraints (pubmed.ncbi.nlm.nih.gov). However, direct mutations of RASA3 in sporadic cancers are not commonly reported; its role in cancer is thought to be functionally significant (through Ras hyperactivation) rather than as a frequent mutational target.

Regulator of Rap1 and Integrin Signaling in Platelets

One of the most prominent roles of RASA3 is in the regulation of platelet activation and blood clotting, via its action on Rap1. Platelets (the cell fragments responsible for blood clot formation) are critically controlled by the small GTPase Rap1. Upon vascular injury, Rap1 triggers “inside-out” signaling that activates platelet integrin receptors (especially αIIbβ3), allowing platelets to aggregate and form a clot. To prevent inappropriate clotting, Rap1 activity in resting platelets is kept low. RASA3 is the chief GAP that inactivates Rap1 in platelets, counterbalancing the Rap1 activator CalDAG-GEFI (a guanine nucleotide exchange factor) (pmc.ncbi.nlm.nih.gov). In other words, platelet Rap1 activation is a push–pull system: CalDAG-GEFI rapidly loads Rap1 with GTP in response to calcium and DAG signals, and RASA3 hydrolyzes that GTP to turn Rap1 off (pmc.ncbi.nlm.nih.gov). This balance ensures that platelets only fully activate when the proper signals are received. Genetic studies have confirmed RASA3’s essential role in this process. Mice lacking functional Rasa3 exhibit severe thrombocytopenia (low platelets) and a tendency for platelets to become spontaneously activated, leading to intermittent episodes of platelet consumption – observations made in both the scat mutant and tissue-specific Rasa3 knockouts (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). In one study, megakaryocyte-specific ablation of Rasa3 caused defects in proplatelet formation and aberrant integrin signaling, due to unrestrained Rap1 activity in these cells (pmc.ncbi.nlm.nih.gov). Similarly, Stefanini et al. (2015) showed that RASA3 is a critical inhibitor of Rap1-dependent platelet activation: platelets without RASA3 had elevated baseline levels of Rap1-GTP and exhibited excessive integrin αIIbβ3 activation even in the absence of stimuli (pmc.ncbi.nlm.nih.gov). As a consequence, such platelets are prone to aggregate inappropriately, and the mice suffer from bleeding abnormalities despite paradoxical platelet activation (because the hyperactive platelets get cleared or degranulated) (pmc.ncbi.nlm.nih.gov). Thus, RASA3 sets an activation threshold in platelets, preventing unwarranted clotting. Upon a real wound or pro-thrombotic signal, second messengers (like PI3K products and Ca²⁺) inhibit RASA3, allowing Rap1 to rapidly turn on and prompt integrin-mediated clot formation (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). After a clot is formed, RASA3 likely helps turn off Rap1 during the “outside-in” signaling phase that consolidates the clot – indeed, RASA3 has been implicated in moderating integrin outside-in signaling as well (pmc.ncbi.nlm.nih.gov). For example, an in-depth biochemical study showed that RASA3’s PIP₃-binding PH domain can localize to sites of integrin signaling and that altering this interaction affects platelet spreading and clot retraction signals (pmc.ncbi.nlm.nih.gov). Clinically, the importance of RASA3 is highlighted by inherited platelet disorders: the scat mutation in mice is a model of thrombocytopenia due to a RASA3 defect, and it mirrors key aspects of certain human platelet function disorders. In summary, in the platelet lineage RASA3 functions as a safeguard to ensure Rap1 (and integrin) activation is appropriately timed and limited, which is essential for normal hemostasis (pmc.ncbi.nlm.nih.gov).

Gatekeeper of T Cell Activation and Adhesion

Beyond the blood production lineages, RASA3 also plays a pivotal role in the immune system, particularly in T lymphocytes. T cells require precise regulation of the small GTPases Ras and Rap1 during their activation: Ras drives proliferation and gene expression via the MAPK pathway, while Rap1 controls integrin-mediated adhesion (such as LFA-1 binding to ICAM-1) which governs T cell trafficking and immunological synapse formation. Recent research has identified RASA3 (along with the related GAP RASA2) as a key “brake” or gatekeeper on T cell activation (pmc.ncbi.nlm.nih.gov). In naive T cells, basal Ras and Rap1 activity must be kept low to prevent inappropriate activation or adhesion. RASA3 is highly expressed in T cells and restrains these GTPases until a true antigenic stimulus occurs (pmc.ncbi.nlm.nih.gov). T cells genetically deficient in RASA3 show clear phenotypes that underscore this role: loss of RASA3 leads to hyper-responsiveness and aberrant adhesion. For example, mice with Rasa3 selectively knocked out in T cells (Rasa3^fl/fl CD4-Cre) have abnormally low numbers of circulating T cells and accumulation of T cells in lymphoid organs (pmc.ncbi.nlm.nih.gov). This is explained by the fact that RASA3-deficient T cells have increased Rap1 activity, causing their integrin LFA-1 to remain in a high-affinity state that locks the cells onto integrin ligands in lymph nodes (impairing their egress and circulation) (pmc.ncbi.nlm.nih.gov). In experimental assays, naive Rasa3-null T cells showed a marked increase in binding to ICAM-1 upon TCR stimulation – much greater than that seen in wild-type T cells – indicating that RASA3 normally suppresses integrin activation downstream of the T cell receptor (pmc.ncbi.nlm.nih.gov). These cells also exhibited enhanced spontaneous proliferation and morphological changes consistent with increased adherence and motility in response to chemokines (pmc.ncbi.nlm.nih.gov). Notably, RASA3 appears to preferentially impact Rap1-mediated adhesion pathways in T cells, while the related RasGAP RASA2 predominantly regulates Ras/MAPK signaling (pmc.ncbi.nlm.nih.gov). Thus, RASA3 serves as the principal Rap1-GAP in T lymphocytes, preventing premature or excessive integrin engagement. In the absence of RASA3, T cells tend to become over-adhesive and hyperactivated, which paradoxically can lead to functional impairments – for instance, RASA3-deficient T cells mounted poorer antibody responses to immunization, likely because their dysregulated adhesion interfered with normal T cell trafficking and interactions (pmc.ncbi.nlm.nih.gov). In a broader sense, RASA3 helps maintain immune homeostasis by keeping resting T cells in a non-adhesive, quiescent state (pmc.ncbi.nlm.nih.gov). Only when proper antigenic and co-stimulatory signals occur (which trigger PLCγ and PI3K pathways, generating IP₃, IP₄, and PIP₃) is RASA3 transiently inhibited so that Rap1 can promote firm adhesion and Ras can drive proliferative signaling. This concept of RASA3 as a checkpoint is supported by in vivo models of autoimmunity and T cell differentiation. For example, emerging evidence suggests RASA3 might influence the balance of T helper cell subsets: one study reported that RASA3 deficiency skews T cells away from pathogenic Th17 cell development toward a Th2-biased program (academic.oup.com), consistent with the idea that altered Ras/Rap signals can change transcriptional outcomes. Moreover, CRISPR-based screens of T cells have repeatedly identified RASA3 as an important regulator: RASA3 knockout was enriched in screens for genes that, when lost, increase T cell adhesion and activation marker expression (pmc.ncbi.nlm.nih.gov). In summary, RASA3 in the immune system functions to set thresholds for cell activation and adhesion, particularly by limiting Rap1-driven integrin activation in T cells (and likely in other leukocytes such as B cells or myeloid cells that also utilize Rap1 for adhesion). This gatekeeper role is crucial to prevent inappropriate immune cell activation and to fine-tune immune responses.

Concluding Remarks

RASA3 emerges as a multifaceted regulator of intracellular signaling, connecting membrane lipid signals to the control of Ras and Rap1 GTPases. Its primary biochemical role is to serve as a GTPase-activator protein for Ras and Rap1, thereby negatively regulating pathways like MAPK signaling and integrin-mediated adhesion. The protein’s complex domain structure (two C2 domains, one PH domain, and a GAP domain) enables it to be acutely regulated by second messengers (Ca²⁺, IP₄, PIP₃). This regulation allows RASA3 to act as a switch – active under resting conditions to keep signaling quiescent, and transiently inactivated when cells need to turn on Ras or Rap1. RASA3 carries out vital functions in several biological contexts. In hematopoiesis, it has a critical, non-redundant role in red blood cell and platelet development (pmc.ncbi.nlm.nih.gov), ensuring that Ras and Rap1 activation levels are properly balanced during cell maturation. In platelets, RASA3 is the major brake on Rap1, preventing accidental platelet activation and thrombosis. In T cells, it is a key checkpoint maintaining immune tolerance and proper trafficking by restraining integrin activation until it’s needed. These specific roles underscore a common theme: RASA3 sets thresholds in signaling pathways to prevent overactivation – a failure of which leads to pathological outcomes (anemia, thrombocytopenia, or immune dysregulation). Experimental evidence from mouse models (e.g. the scat mutant and conditional knockouts) and human genetic studies (RASA3 mutation causing Rasopathy-like disease) provide strong support for RASA3’s importance in normal physiology (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).

From a clinical and therapeutic perspective, RASA3’s position at the nexus of lipid second messengers and Ras-family GTPases makes it a potential target of interest. For instance, modulating RASA3 activity might be beneficial in certain immune conditions or clotting disorders – e.g. temporarily inhibiting RASA3 could boost T cell adhesion in cancer immunotherapy (similar in concept to RASA3-deficient T cells showing enhanced activation (pmc.ncbi.nlm.nih.gov)), whereas enhancing RASA3 function might restrain unwanted platelet activation in prothrombotic states. Additionally, given its role in restraining Ras, RASA3 could be considered a tumor suppressor candidate; loss of RASA3 might contribute to oncogenic Ras signaling in some contexts (pubmed.ncbi.nlm.nih.gov). Current research (as of 2023–2024) continues to explore these angles, with Trends in Immunology highlighting RASA3 as a “gatekeeper” of T cell activation (pmc.ncbi.nlm.nih.gov) and case studies identifying RASA3 mutations in human disease (pmc.ncbi.nlm.nih.gov). In conclusion, RASA3 is a vital signaling regulator that links lipid signaling to Ras and Rap1 GTPase activity, with well-demonstrated roles in blood cell development, hemostasis, and immune cell function. Its precise control over GTPase switches exemplifies how cells maintain signaling balance, and disruptions of RASA3 can have wide-ranging consequences for organismal health. All these insights are backed by accumulating experimental evidence from the past decade, solidifying our current understanding of RASA3’s functional annotation in human biology.

References: The above report is based on a synthesis of recent authoritative sources, including primary research articles and reviews. Key sources include: Cullen et al., 1995 (Nature) – identification of RASA3 as an IP₄-binding RasGAP (pmc.ncbi.nlm.nih.gov); Kupzig et al., 2006 & 2009 – biochemical characterization of RASA3’s GAP activity on Ras/Rap1 and catalytic mechanism (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov); Blanc et al., 2012 (PNAS) – the scat mouse model demonstrating RASA3’s essential role in erythropoiesis and megakaryopoiesis (pmc.ncbi.nlm.nih.gov); Molina-Ortiz et al., 2014 (PLoS Genet) and Stefanini et al., 2015 (J. Clin. Invest) – RASA3 control of Rap1 in megakaryocytes/platelets (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov); Battram et al., 2017 (J. Biol. Chem) – regulation of integrin signaling by RASA3’s PH domain (pmc.ncbi.nlm.nih.gov); and Johansen et al., 2023 (Trends Immunol) – review of RASA3 as a gatekeeper in T cell activation (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). A 2023 clinical report by Ayaz et al. (J Pediatr Genet) provided evidence of a human RASA3 loss-of-function mutation causing Ras/MAPK pathway dysregulation (pmc.ncbi.nlm.nih.gov). All claims and data in this report are supported by these and other cited sources. The citations (in 【】) refer to specific lines in the source documents for verification of each statement.

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19. AnnotationURLCitation(end_index=7867, start_index=7716, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=be%20inactivated%20by%20PI3K%20and,suggesting%20that%20PI3K%20acts')
20. AnnotationURLCitation(end_index=8568, start_index=8455, title='The Ras/Rap GTPase activating protein RASA3: from gene structure to in vivo functions - PubMed', type='url_citation', url='https://pubmed.ncbi.nlm.nih.gov/25294679/#:~:text=GAP1,1%2C3%2C4%2C5%29P4%20receptor')
21. AnnotationURLCitation(end_index=9572, start_index=9401, title='Critical function for the Ras-GTPase activating protein RASA3 in vertebrate erythropoiesis and megakaryopoiesis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3409772/#:~:text=regulatory%20feedback%20mechanism%20common%20to,is%20also%20defective%20during%20crisis')
22. AnnotationURLCitation(end_index=9866, start_index=9704, title='Critical function for the Ras-GTPase activating protein RASA3 in vertebrate erythropoiesis and megakaryopoiesis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3409772/#:~:text=Ras%20GTPase%20activating%20protein%20,is%20also%20defective%20during%20crisis')
23. AnnotationURLCitation(end_index=10150, start_index=9988, title='Critical function for the Ras-GTPase activating protein RASA3 in vertebrate erythropoiesis and megakaryopoiesis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3409772/#:~:text=Ras%20GTPase%20activating%20protein%20,is%20also%20defective%20during%20crisis')
24. AnnotationURLCitation(end_index=11043, start_index=10881, title='Critical function for the Ras-GTPase activating protein RASA3 in vertebrate erythropoiesis and megakaryopoiesis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3409772/#:~:text=Ras%20GTPase%20activating%20protein%20,is%20also%20defective%20during%20crisis')
25. AnnotationURLCitation(end_index=11192, start_index=11044, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=domain%20structures%2C%20including%20GAP%20domains,binding%20C2')
26. AnnotationURLCitation(end_index=12250, start_index=12073, title='Critical function for the Ras-GTPase activating protein RASA3 in vertebrate erythropoiesis and megakaryopoiesis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3409772/#:~:text=Ras%20GTPase%20activating%20protein%20,critical%2C%20conserved%2C%20and%20nonredundant%20role')
27. AnnotationURLCitation(end_index=12549, start_index=12388, title='Critical function for the Ras-GTPase activating protein RASA3 in vertebrate erythropoiesis and megakaryopoiesis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3409772/#:~:text=scat%20red%20cells%20where%20it,for%20RASA3%20in%20vertebrate%20hematopoiesis')
28. AnnotationURLCitation(end_index=12838, start_index=12670, title='Critical function for the Ras-GTPase activating protein RASA3 in vertebrate erythropoiesis and megakaryopoiesis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3409772/#:~:text=The%20recessive%20mutant%20scat%20,catastrophic%20hematopoietic%20failure%20in%20the')
29. AnnotationURLCitation(end_index=13223, start_index=13107, title='A Novel Autosomal Recessive Candidate Gene Responsible for RASopathy-Like Phenotype and Bone Marrow Failure: RASA3 - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC11288707/#:~:text=had%20low,MAPK%20pathway.%20The')
30. AnnotationURLCitation(end_index=13608, start_index=13474, title='A Novel Autosomal Recessive Candidate Gene Responsible for RASopathy-Like Phenotype and Bone Marrow Failure: RASA3 - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC11288707/#:~:text=bone%20marrow%20failure%20are%20known,RASopathies')
31. AnnotationURLCitation(end_index=13773, start_index=13609, title='A Novel Autosomal Recessive Candidate Gene Responsible for RASopathy-Like Phenotype and Bone Marrow Failure: RASA3 - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC11288707/#:~:text=which%20are%20characterized%20by%20many,of%20RASopathy%20genes%20was%20observed')
32. AnnotationURLCitation(end_index=14013, start_index=13897, title='A Novel Autosomal Recessive Candidate Gene Responsible for RASopathy-Like Phenotype and Bone Marrow Failure: RASA3 - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC11288707/#:~:text=had%20low,MAPK%20pathway.%20The')
33. AnnotationURLCitation(end_index=14440, start_index=14263, title='Critical function for the Ras-GTPase activating protein RASA3 in vertebrate erythropoiesis and megakaryopoiesis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3409772/#:~:text=Ras%20GTPase%20activating%20protein%20,critical%2C%20conserved%2C%20and%20nonredundant%20role')
34. AnnotationURLCitation(end_index=14572, start_index=14441, title='A Novel Autosomal Recessive Candidate Gene Responsible for RASopathy-Like Phenotype and Bone Marrow Failure: RASA3 - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC11288707/#:~:text=%28Ras,of%20RASopathy%20genes%20was%20observed')
35. AnnotationURLCitation(end_index=14874, start_index=14700, title='A Novel Autosomal Recessive Candidate Gene Responsible for RASopathy-Like Phenotype and Bone Marrow Failure: RASA3 - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC11288707/#:~:text=which%20are%20characterized%20by%20many,putative%20function%20module%2C%20which%20further')
36. AnnotationURLCitation(end_index=15179, start_index=15025, title='Critical function for the Ras-GTPase activating protein RASA3 in vertebrate erythropoiesis and megakaryopoiesis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3409772/#:~:text=the%20second%20crisis%20,for%20RASA3%20in%20vertebrate%20hematopoiesis')
37. AnnotationURLCitation(end_index=15709, start_index=15515, title='The Ras/Rap GTPase activating protein RASA3: from gene structure to in vivo functions - PubMed', type='url_citation', url='https://pubmed.ncbi.nlm.nih.gov/25294679/#:~:text=Keywords%3A%20Cancer%3B%20GTPase%20activating%20protein%3B,Megakaryocyte%3B%20Platelet%3B%20RASA3%3B%20Rap%3B%20Ras')
38. AnnotationURLCitation(end_index=16745, start_index=16653, title='RASA3 is a critical inhibitor of RAP1-dependent platelet activation - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC4396462/#:~:text=Abstract')
39. AnnotationURLCitation(end_index=17034, start_index=16942, title='RASA3 is a critical inhibitor of RAP1-dependent platelet activation - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC4396462/#:~:text=Abstract')
40. AnnotationURLCitation(end_index=17652, start_index=17484, title='Critical function for the Ras-GTPase activating protein RASA3 in vertebrate erythropoiesis and megakaryopoiesis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3409772/#:~:text=The%20recessive%20mutant%20scat%20,catastrophic%20hematopoietic%20failure%20in%20the')
41. AnnotationURLCitation(end_index=17767, start_index=17653, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=%2A%2049.Molina,trisphosphate')
42. AnnotationURLCitation(end_index=18060, start_index=17946, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=%2A%2049.Molina,trisphosphate')
43. AnnotationURLCitation(end_index=18423, start_index=18331, title='RASA3 is a critical inhibitor of RAP1-dependent platelet activation - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC4396462/#:~:text=Abstract')
44. AnnotationURLCitation(end_index=18818, start_index=18650, title='Critical function for the Ras-GTPase activating protein RASA3 in vertebrate erythropoiesis and megakaryopoiesis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3409772/#:~:text=The%20recessive%20mutant%20scat%20,catastrophic%20hematopoietic%20failure%20in%20the')
45. AnnotationURLCitation(end_index=19263, start_index=19096, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=Furthermore%2C%20although%20most%20proteins%20with,suggesting%20that%20PI3K%20acts')
46. AnnotationURLCitation(end_index=19356, start_index=19264, title='RASA3 is a critical inhibitor of RAP1-dependent platelet activation - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC4396462/#:~:text=Abstract')
47. AnnotationURLCitation(end_index=19676, start_index=19570, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=,PMC%20free%20article')
48. AnnotationURLCitation(end_index=20004, start_index=19898, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=,PMC%20free%20article')
49. AnnotationURLCitation(end_index=20528, start_index=20436, title='RASA3 is a critical inhibitor of RAP1-dependent platelet activation - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC4396462/#:~:text=Abstract')
50. AnnotationURLCitation(end_index=21316, start_index=21149, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=mediating%20T%20cell%20activation%2C%20the,T%20cell%20activation%20and%20migration')
51. AnnotationURLCitation(end_index=21700, start_index=21534, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=induce%20MAPK%20pathways%20and%20cellular,T%20cell%20activation%20and%20migration')
52. AnnotationURLCitation(end_index=22152, start_index=22045, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=match%20at%20L498%20,4')
53. AnnotationURLCitation(end_index=22529, start_index=22410, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=datasets%20of%20T%20cell%20gene,Of')
54. AnnotationURLCitation(end_index=22917, start_index=22798, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=datasets%20of%20T%20cell%20gene,Of')
55. AnnotationURLCitation(end_index=23224, start_index=23082, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=migration%2C%20and%20localization%20,GAP%20in%20T%20cells')
56. AnnotationURLCitation(end_index=23563, start_index=23396, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=mediating%20T%20cell%20activation%2C%20the,T%20cell%20activation%20and%20migration')
57. AnnotationURLCitation(end_index=24100, start_index=24013, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=,4')
58. AnnotationURLCitation(end_index=24347, start_index=24228, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=datasets%20of%20T%20cell%20gene,Of')
59. AnnotationURLCitation(end_index=25115, start_index=24933, title='RAS P21 Protein Activator 3 (RASA3) specifically promotes pathogenic T helper 17 cell generation by repressing T helper 2-biased programs | The Journal of Immunology | Oxford Academic', type='url_citation', url='https://academic.oup.com/jimmunol/article/202/1_Supplement/128.13/7956849#:~:text=Th17%20cells%20that%20produce%20the,a%20GTPase%20activating%20protein%2C%20was')
60. AnnotationURLCitation(end_index=25571, start_index=25434, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=Rasa3,also%20showed%20increased%20proliferation%20in')
61. AnnotationURLCitation(end_index=26989, start_index=26835, title='Critical function for the Ras-GTPase activating protein RASA3 in vertebrate erythropoiesis and megakaryopoiesis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3409772/#:~:text=the%20second%20crisis%20,for%20RASA3%20in%20vertebrate%20hematopoiesis')
62. AnnotationURLCitation(end_index=27965, start_index=27788, title='Critical function for the Ras-GTPase activating protein RASA3 in vertebrate erythropoiesis and megakaryopoiesis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3409772/#:~:text=Ras%20GTPase%20activating%20protein%20,critical%2C%20conserved%2C%20and%20nonredundant%20role')
63. AnnotationURLCitation(end_index=28082, start_index=27966, title='A Novel Autosomal Recessive Candidate Gene Responsible for RASopathy-Like Phenotype and Bone Marrow Failure: RASA3 - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC11288707/#:~:text=had%20low,MAPK%20pathway.%20The')
64. AnnotationURLCitation(end_index=28663, start_index=28526, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=Rasa3,also%20showed%20increased%20proliferation%20in')
65. AnnotationURLCitation(end_index=29142, start_index=28948, title='The Ras/Rap GTPase activating protein RASA3: from gene structure to in vivo functions - PubMed', type='url_citation', url='https://pubmed.ncbi.nlm.nih.gov/25294679/#:~:text=Keywords%3A%20Cancer%3B%20GTPase%20activating%20protein%3B,Megakaryocyte%3B%20Platelet%3B%20RASA3%3B%20Rap%3B%20Ras')
66. AnnotationURLCitation(end_index=29467, start_index=29300, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=mediating%20T%20cell%20activation%2C%20the,T%20cell%20activation%20and%20migration')
67. AnnotationURLCitation(end_index=29646, start_index=29530, title='A Novel Autosomal Recessive Candidate Gene Responsible for RASopathy-Like Phenotype and Bone Marrow Failure: RASA3 - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC11288707/#:~:text=had%20low,MAPK%20pathway.%20The')
68. AnnotationURLCitation(end_index=30557, start_index=30455, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=,Google%20Scholar')
69. AnnotationURLCitation(end_index=30781, start_index=30679, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=,Google%20Scholar')
70. AnnotationURLCitation(end_index=30888, start_index=30782, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=,PMC%20free%20article')
71. AnnotationURLCitation(end_index=31185, start_index=31017, title='Critical function for the Ras-GTPase activating protein RASA3 in vertebrate erythropoiesis and megakaryopoiesis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3409772/#:~:text=Ras%20GTPase%20activating%20protein%20,for%20RASA3%20in%20vertebrate%20hematopoiesis')
72. AnnotationURLCitation(end_index=31441, start_index=31327, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=%2A%2049.Molina,trisphosphate')
73. AnnotationURLCitation(end_index=31534, start_index=31442, title='RASA3 is a critical inhibitor of RAP1-dependent platelet activation - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC4396462/#:~:text=Abstract')
74. AnnotationURLCitation(end_index=31758, start_index=31631, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=match%20at%20L1143%20,PMC%20free%20article')
75. AnnotationURLCitation(end_index=32027, start_index=31860, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=mediating%20T%20cell%20activation%2C%20the,T%20cell%20activation%20and%20migration')
76. AnnotationURLCitation(end_index=32147, start_index=32028, title='Mind the GAP: RASA2 and RASA3 GTPase Activating Proteins as gatekeepers of T cell activation and adhesion - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10621891/#:~:text=datasets%20of%20T%20cell%20gene,Of')
77. AnnotationURLCitation(end_index=32423, start_index=32307, title='A Novel Autosomal Recessive Candidate Gene Responsible for RASopathy-Like Phenotype and Bone Marrow Failure: RASA3 - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC11288707/#:~:text=had%20low,MAPK%20pathway.%20The')