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this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.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 overview
- Verified identity and nomenclature for CAPG (human macrophage-capping protein; UniProt P40121), including family/domains and synonyms (gCap39). Gathered recent literature emphasizing function, regulation, localization, and disease relevance. Extracted mechanistic details (barbed-end capping, Ca2+/PIP2 and redox regulation), nucleo-cytoplasmic dynamics, and cancer biology (invasion/metastasis, biomarker and pathway links). Where possible, URLs and publication dates are provided.

Table: Concise evidence table for human CAPG (UniProt P40121) summarizing identity, biochemical activity, regulation, localization, and cancer relevance with primary sources and context citations.

1) Key concepts and definitions
- Identity and family context. CAPG is the human macrophage-capping protein (also called gCap39) belonging to the gelsolin/villin superfamily. It comprises three gelsolin-like domains (C1–C3), consistent with gelsolin-family architecture (as opposed to six domains in gelsolin). Structural studies of human CapG fragments and comparative analyses firmly place it in this family (2012; URL: https://doi.org/10.14288/1.0062292). CAPG is human in the sources cited and frequently studied in human cell contexts (2021; URL: https://doi.org/10.1016/j.freeradbiomed.2021.02.038) (jiang2012structuralinvestigationof pages 59-65, jiang2012structuralinvestigationof pages 32-37, prescher2021themigrationbehavior pages 12-12).
- Primary biochemical function. CAPG is primarily an actin barbed-end capping protein: it reversibly blocks barbed ends of filaments to modulate polymerization dynamics. In contrast to gelsolin, native CAPG does not sever filaments under typical conditions, although engineered mutants can acquire severing activity (2012; URL: https://doi.org/10.14288/1.0062292; 2021; URL: https://doi.org/10.1016/j.freeradbiomed.2021.02.038) (jiang2012structuralinvestigationof pages 37-42, prescher2021themigrationbehavior pages 12-12).
- Regulation. CAPG is regulated by calcium and polyphosphoinositides (notably PIP2), with Ca2+ favoring activated conformations and PIP2 antagonizing capping; these inputs enable rapid and reversible control during cell signaling and membrane remodeling (2012; URL: https://doi.org/10.14288/1.0062292) (jiang2012structuralinvestigationof pages 106-109, jiang2012structuralinvestigationof pages 37-42). CAPG is also redox-sensitive: cysteines C282 and C290 (the latter unique to CAPG) undergo reversible oxidation that affects localization and migration (2021; URL: https://doi.org/10.1016/j.freeradbiomed.2021.02.038) (prescher2021themigrationbehavior pages 9-11, prescher2021themigrationbehavior pages 12-12).
- Subcellular localization. CAPG localizes to cytoplasm and nucleus, with dynamic nucleo-cytoplasmic shuttling. In the nucleus, most CAPG is freely diffusing and a minor fraction appears immobilized; oxidative conditions reduce nuclear CAPG levels in a manner dependent on C282/C290. Importin-β–dependent nuclear import and a role for CAPG nuclear pools in invasion have been reported; in HCC tissues CAPG staining was predominantly cytoplasmic (2018; URL: https://doi.org/10.21873/anticanres.12680; 2021; URL: https://doi.org/10.1016/j.freeradbiomed.2021.02.038) (prescher2021themigrationbehavior pages 11-12, tsai2018gelsolinlikeactincappingprotein pages 6-8).

2) Recent developments and latest research (priority 2023–2024)
- Super-enhancer regulation and AML. Recent work identifies CAPG as a super-enhancer–associated gene that promotes AML progression via NF-κB pathway regulation; CAPG knockdown exhausted AML cells and prolonged survival in an MLL-AF9 mouse model (2023; Communications Biology; DOI referenced in 2025 review). In addition, FYB1-targeted modulation of CAPG promotes AML progression; FYB1 knockdown lowers CAPG and limits tumorigenic phenotypes, nominating the FYB1–CAPG axis as a therapeutic thread (May 2025; URL: https://doi.org/10.1007/s11010-024-04992-4). These observations underscore CAPG as an emerging epigenetic/oncogenic node in myeloid malignancy (liu2025fyb1targetedmodulationof pages 14-15).
- Redox-sensitive regulation in glioblastoma. CAPG’s C282/C290 mediate redox-responsive localization and migration changes; H2O2 shifts CAPG out of the nucleus, and C282S or C290S mutants diminish migration. CAPG interacts with RAVER1 and may be recruited to adhesion complexes in a redox-dependent manner, linking oxidative stress to cytoskeletal remodeling (May 2021; URL: https://doi.org/10.1016/j.freeradbiomed.2021.02.038). Although just outside the 2023–2024 window, this recent mechanistic work remains the most specific redox study (prescher2021themigrationbehavior pages 9-11, prescher2021themigrationbehavior pages 11-12).
- Structural and regulatory refinements. Comparative structural analyses reinforce that CAPG’s gelsolin-like domains adopt activated conformations under Ca2+ and that PIP2 antagonizes capping, providing a molecular basis for spatiotemporal control at membranes and leading edges (2012; URL: https://doi.org/10.14288/1.0062292). These principles underpin newer observations in cancer models where CAPG supports motility and invasion (jiang2012structuralinvestigationof pages 59-65, jiang2012structuralinvestigationof pages 37-42).

3) Current applications and real-world implementations
- Oncology biomarkers and prognosis. Cytoplasmic CAPG overexpression is associated with increased invasion/migration and poorer prognosis in HCC tissues, suggesting utility as a prognostic biomarker in clinical histopathology workflows (Jul 2018; URL: https://doi.org/10.21873/anticanres.12680) (tsai2018gelsolinlikeactincappingprotein pages 6-8, tsai2018gelsolinlikeactincappingprotein pages 8-8). In glioma, CAPG staining intensifies with higher tumor grade, and nuclear/cytoplasmic distribution shows heterogeneity that may reflect ROS/IDH status, supporting exploratory use in tumor characterization (May 2021; URL: https://doi.org/10.1016/j.freeradbiomed.2021.02.038) (prescher2021themigrationbehavior pages 11-12).
- Therapeutic targeting concepts. The identification of CAPG as a super-enhancer–associated driver in AML, and as a downstream effector of FYB1 in AML progression, supports strategies to: (a) pharmacologically disrupt super-enhancer activity at CAPG; (b) target upstream regulators (e.g., FYB1) to down-modulate CAPG; or (c) develop CAPG-directed inhibitors or degraders. These proposals are supported by in vitro and in vivo data indicating that CAPG suppression impairs proliferation and promotes apoptosis in AML cells (May 2025; URL: https://doi.org/10.1007/s11010-024-04992-4) (liu2025fyb1targetedmodulationof pages 14-15). While not yet in clinical trials in our retrieved evidence, these define plausible translational paths.

4) Expert opinions and analysis from authoritative sources
- Mechanistic role in actin dynamics. Structural and biochemical analyses converge on CAPG’s role as a Ca2+/PIP2-regulated actin barbed-end capper, acting as a tunable molecular gate for filament elongation at membranes. This aligns with models where PIP2-rich membranes locally modulate capping, and Ca2+ transients activate capping to sculpt lamellipodial dynamics; CAPG’s lower actin affinity than gelsolin suggests it favors rapid, reversible control rather than persistent remodeling (2012; URL: https://doi.org/10.14288/1.0062292) (jiang2012structuralinvestigationof pages 37-42, jiang2012structuralinvestigationof pages 32-37, jiang2012structuralinvestigationof pages 79-85).
- Nuclear functions and invasion. Nuclear CAPG pools appear functionally relevant: in glioblastoma, forced nuclear export abrogated CAPG-induced invasion, while importin-β–dependent nuclear entry has been linked with invasive behavior in other cell models. Together, these data support a dual-compartment model where cytoplasmic CAPG controls barbed-end dynamics at the cortex, while nuclear CAPG modulates transcriptional programs supporting invasion and therapy resistance (2018; URL: https://doi.org/10.21873/anticanres.12680; 2021; URL: https://doi.org/10.1016/j.freeradbiomed.2021.02.038) (tsai2018gelsolinlikeactincappingprotein pages 6-8, prescher2021themigrationbehavior pages 11-12).
- Redox regulation as a contextual switch. The identification of C282/C290 as redox switches controlling localization and migration integrates CAPG into ROS-driven signaling common in tumors, helping explain observed grade-associated staining and potential links to IDH-mutant metabolic states in gliomas (May 2021; URL: https://doi.org/10.1016/j.freeradbiomed.2021.02.038) (prescher2021themigrationbehavior pages 9-11, prescher2021themigrationbehavior pages 11-12).

5) Relevant statistics and data from recent studies
- HCC prognosis and invasion/migration. Tsai et al. reported significant associations between CAPG overexpression and worse patient survival, and demonstrated that CAPG knockdown suppressed migration in Hep3B cells (p-values reported as p<0.05, p<0.01, **p<0.001 for migration assays). The study emphasized cytoplasmic overexpression in tumor tissues (Jul 2018; URL: https://doi.org/10.21873/anticanres.12680). Specific hazard ratios were not provided in the excerpted evidence, but the direction of effect (worse prognosis with higher CAPG) is clear (tsai2018gelsolinlikeactincappingprotein pages 6-8, tsai2018gelsolinlikeactincappingprotein pages 8-8).
- Glioblastoma redox sensitivity and migration. Prescher et al. documented that oxidation via H2O2 reduces nuclear CAPG, and mutation of C282/C290 (Cys→Ser) decreases migration. Quantitatively, nuclear mobility analyses indicated most CAPG is freely diffusing in the nucleus with approximately 12% slowed and up to 0–3% immobilized, highlighting dynamic behavior (May 2021; URL: https://doi.org/10.1016/j.freeradbiomed.2021.02.038) (prescher2021themigrationbehavior pages 11-12).
- AML preclinical efficacy signals. FYB1 knockdown reduced CAPG expression, inhibited proliferation, promoted apoptosis, and reduced tumor formation in mice; CAPG suppression alone also curtailed proliferation and increased apoptosis, nominating CAPG as a functional driver (May 2025; URL: https://doi.org/10.1007/s11010-024-04992-4). While not a 2023–2024 publication, these data contextualize 2023 epigenetic findings and suggest therapeutic avenues (liu2025fyb1targetedmodulationof pages 14-15).

Functional synthesis: mechanism, pathways, and cellular context
- Biochemical role. CAPG caps actin filament barbed ends to tune filament elongation; it is generally non-severing under physiological conditions, distinguishing it from gelsolin. Ca2+ promotes active conformations of the gelsolin-like domains; PIP2 binding antagonizes capping, allowing leading-edge control, while redox switches at C282/C290 modulate nuclear-cytoplasmic distribution and migration (2012; 2021) (jiang2012structuralinvestigationof pages 37-42, jiang2012structuralinvestigationof pages 106-109, prescher2021themigrationbehavior pages 9-11, prescher2021themigrationbehavior pages 11-12).
- Cellular location of action. CAPG acts at the cell cortex and adhesion complexes to influence protrusion and motility, and in the nucleus where it likely participates in transcriptional regulation supporting invasion and therapy resistance. The balance between cytoplasmic and nuclear CAPG is dynamic and sensitive to oxidative state (2018; 2021) (tsai2018gelsolinlikeactincappingprotein pages 6-8, prescher2021themigrationbehavior pages 11-12).
- Pathways. In solid tumors, CAPG supports actin-dependent migration and invasion and may integrate with adhesion machinery (e.g., RAVER1-associated complexes). In AML, CAPG is linked to NF-κB pathway regulation and super-enhancer control, and it is influenced by upstream FYB1, indicating that CAPG sits within oncogenic transcriptional circuits as well as cytoskeletal programs (2023–2025) (liu2025fyb1targetedmodulationof pages 14-15).

Mandatory verification outcomes
- Gene symbol and protein match. CAPG encodes the macrophage-capping protein (gCap39), a gelsolin/villin-family protein with gelsolin-like domains (C1–C3). The functions and family assignment align with the UniProt P40121 entry (2012; 2021) (jiang2012structuralinvestigationof pages 32-37, prescher2021themigrationbehavior pages 12-12, jiang2012structuralinvestigationof pages 59-65).
- Organism. All cited primary functional/structural work references human CAPG or human cell models (2012; 2021; 2018) (jiang2012structuralinvestigationof pages 59-65, prescher2021themigrationbehavior pages 12-12, tsai2018gelsolinlikeactincappingprotein pages 6-8).
- Domains/family. Gelsolin/villin superfamily membership is consistently supported by structural and sequence analyses; CAPG possesses gelsolin-like domains and lacks the severing activity characteristic of gelsolin’s multi-domain configuration (2012) (jiang2012structuralinvestigationof pages 79-85, jiang2012structuralinvestigationof pages 37-42).
- Ambiguity check. No conflicting gene symbol usage was found within the cited human literature; references consistently map CAPG to the human macrophage-capping protein. If encountering similarly named condensin genes (NCAPG/NCAPG2) in other databases, note these are unrelated condensin subunits and not the actin-regulatory CAPG (not cited here; genomic distinction recommended in practice).

Evidence limitations and open questions
- Quantitative clinical metrics (e.g., hazard ratios, therapy-response effect sizes) for CAPG as a biomarker were limited in the accessible excerpts. Further granularity, especially for 2023–2024 datasets, would refine translational conclusions. Nonetheless, convergent mechanistic and preclinical data support CAPG’s role in invasion/metastasis and AML progression (tsai2018gelsolinlikeactincappingprotein pages 6-8, liu2025fyb1targetedmodulationof pages 14-15).

References (with URLs and dates)
- Prescher N, Hänsch S, Knobbe-Thomsen CB, et al. The migration behavior of human glioblastoma cells is influenced by the redox-sensitive human macrophage capping protein CAPG. Free Radic Biol Med. 2021 May;167:81-93. URL: https://doi.org/10.1016/j.freeradbiomed.2021.02.038 (prescher2021themigrationbehavior pages 9-11, prescher2021themigrationbehavior pages 12-12, prescher2021themigrationbehavior pages 11-12).
- Jiang C. Structural investigation of gelsolin superfamily members. 2012 Jan. URL: https://doi.org/10.14288/1.0062292 (jiang2012structuralinvestigationof pages 59-65, jiang2012structuralinvestigationof pages 37-42, jiang2012structuralinvestigationof pages 79-85, jiang2012structuralinvestigationof pages 32-37, jiang2012structuralinvestigationof pages 106-109).
- Tsai T-J, Chao W-Y, Chen C-C, et al. Gelsolin-like Actin-capping Protein (CapG) Overexpression in the Cytoplasm of Human Hepatocellular Carcinoma, Associated with Cellular Invasion, Migration and Tumor Prognosis. Anticancer Res. 2018 Jul;38(7):3943-3950. URL: https://doi.org/10.21873/anticanres.12680 (tsai2018gelsolinlikeactincappingprotein pages 6-8, tsai2018gelsolinlikeactincappingprotein pages 8-8).
- Liu W, Yin H, Xie Z, et al. FYB1-targeted modulation of CAPG promotes AML progression. Mol Cell Biochem. 2025 May;480:985-999. URL: https://doi.org/10.1007/s11010-024-04992-4 (liu2025fyb1targetedmodulationof pages 14-15).

References

1. (jiang2012structuralinvestigationof pages 106-109): Chenguang Jiang. Structural investigation of gelsolin superfamily members. ArXiv, Jan 2012. URL: https://doi.org/10.14288/1.0062292, doi:10.14288/1.0062292. This article has 0 citations.

2. (prescher2021themigrationbehavior pages 12-12): Nina Prescher, Sebastian Hänsch, Christiane B. Knobbe-Thomsen, Kai Stühler, and Gereon Poschmann. The migration behavior of human glioblastoma cells is influenced by the redox-sensitive human macrophage capping protein capg. Free Radical Biology and Medicine, 167:81-93, May 2021. URL: https://doi.org/10.1016/j.freeradbiomed.2021.02.038, doi:10.1016/j.freeradbiomed.2021.02.038. This article has 26 citations and is from a peer-reviewed journal.

3. (jiang2012structuralinvestigationof pages 37-42): Chenguang Jiang. Structural investigation of gelsolin superfamily members. ArXiv, Jan 2012. URL: https://doi.org/10.14288/1.0062292, doi:10.14288/1.0062292. This article has 0 citations.

4. (prescher2021themigrationbehavior pages 9-11): Nina Prescher, Sebastian Hänsch, Christiane B. Knobbe-Thomsen, Kai Stühler, and Gereon Poschmann. The migration behavior of human glioblastoma cells is influenced by the redox-sensitive human macrophage capping protein capg. Free Radical Biology and Medicine, 167:81-93, May 2021. URL: https://doi.org/10.1016/j.freeradbiomed.2021.02.038, doi:10.1016/j.freeradbiomed.2021.02.038. This article has 26 citations and is from a peer-reviewed journal.

5. (liu2025fyb1targetedmodulationof pages 14-15): Wenyuan Liu, Hongli Yin, Zhiwei Xie, Fang Fang, Jinhua Chu, Linhai Yang, Lingling Huang, Songji Tu, Huaju Cai, Zhengyu Wu, Anbang Wei, Chengzhu Liu, Yi Hong, Xiaotong Tian, Yan Cheng, Jian Pan, Ningling Wang, and Kunlong Zhang. Fyb1-targeted modulation of capg promotes aml progression. Molecular and Cellular Biochemistry, 480:985-999, May 2025. URL: https://doi.org/10.1007/s11010-024-04992-4, doi:10.1007/s11010-024-04992-4. This article has 2 citations and is from a peer-reviewed journal.

6. (prescher2021themigrationbehavior pages 11-12): Nina Prescher, Sebastian Hänsch, Christiane B. Knobbe-Thomsen, Kai Stühler, and Gereon Poschmann. The migration behavior of human glioblastoma cells is influenced by the redox-sensitive human macrophage capping protein capg. Free Radical Biology and Medicine, 167:81-93, May 2021. URL: https://doi.org/10.1016/j.freeradbiomed.2021.02.038, doi:10.1016/j.freeradbiomed.2021.02.038. This article has 26 citations and is from a peer-reviewed journal.

7. (tsai2018gelsolinlikeactincappingprotein pages 6-8): TSUNG-JUNG TSAI, WEN-YING CHAO, CHIEN-CHIN CHEN, YI-JU CHEN, CHING-YEN LIN, and YING-RAY LEE. Gelsolin-like actin-capping protein (capg) overexpression in the cytoplasm of human hepatocellular carcinoma, associated with cellular invasion, migration and tumor prognosis. Anticancer Research, 38:3943-3950, Jul 2018. URL: https://doi.org/10.21873/anticanres.12680, doi:10.21873/anticanres.12680. This article has 20 citations and is from a peer-reviewed journal.

8. (jiang2012structuralinvestigationof pages 32-37): Chenguang Jiang. Structural investigation of gelsolin superfamily members. ArXiv, Jan 2012. URL: https://doi.org/10.14288/1.0062292, doi:10.14288/1.0062292. This article has 0 citations.

9. (jiang2012structuralinvestigationof pages 59-65): Chenguang Jiang. Structural investigation of gelsolin superfamily members. ArXiv, Jan 2012. URL: https://doi.org/10.14288/1.0062292, doi:10.14288/1.0062292. This article has 0 citations.

10. (tsai2018gelsolinlikeactincappingprotein pages 8-8): TSUNG-JUNG TSAI, WEN-YING CHAO, CHIEN-CHIN CHEN, YI-JU CHEN, CHING-YEN LIN, and YING-RAY LEE. Gelsolin-like actin-capping protein (capg) overexpression in the cytoplasm of human hepatocellular carcinoma, associated with cellular invasion, migration and tumor prognosis. Anticancer Research, 38:3943-3950, Jul 2018. URL: https://doi.org/10.21873/anticanres.12680, doi:10.21873/anticanres.12680. This article has 20 citations and is from a peer-reviewed journal.

11. (jiang2012structuralinvestigationof pages 79-85): Chenguang Jiang. Structural investigation of gelsolin superfamily members. ArXiv, Jan 2012. URL: https://doi.org/10.14288/1.0062292, doi:10.14288/1.0062292. This article has 0 citations.

Citations

1. jiang2012structuralinvestigationof pages 106-109
2. prescher2021themigrationbehavior pages 12-12
3. jiang2012structuralinvestigationof pages 37-42
4. prescher2021themigrationbehavior pages 9-11
5. prescher2021themigrationbehavior pages 11-12
6. tsai2018gelsolinlikeactincappingprotein pages 6-8
7. jiang2012structuralinvestigationof pages 32-37
8. jiang2012structuralinvestigationof pages 59-65
9. tsai2018gelsolinlikeactincappingprotein pages 8-8
10. jiang2012structuralinvestigationof pages 79-85
11. https://doi.org/10.14288/1.0062292
12. https://doi.org/10.1016/j.freeradbiomed.2021.02.038
13. https://doi.org/10.1007/s11010-024-04992-4
14. https://doi.org/10.21873/anticanres.12680
15. https://doi.org/10.14288/1.0062292;
16. https://doi.org/10.21873/anticanres.12680;
17. https://doi.org/10.14288/1.0062292,
18. https://doi.org/10.1016/j.freeradbiomed.2021.02.038,
19. https://doi.org/10.1007/s11010-024-04992-4,
20. https://doi.org/10.21873/anticanres.12680,