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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: O88396
• Protein Description: RecName: Full=GrpE protein homolog 2, mitochondrial; AltName: Full=Mt-GrpE#2; Flags: Precursor;
• Gene Information: Name=Grpel2; Synonyms=Mt-grpel2;
• Organism (full): Mus musculus (Mouse).
• Protein Family: Belongs to the GrpE family. .
• Key Domains: GrpE. (IPR000740); GrpE_CC. (IPR013805); GrpE_head. (IPR009012); GrpE (PF01025)

MANDATORY VERIFICATION STEPS:

1. Check if the gene symbol "Grpel2" matches the protein description above
2. Verify the organism is correct: Mus musculus (Mouse).
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 'Grpel2' 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 Grpel2 (gene ID: Grpel2, UniProt: O88396) in mouse.

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this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.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: O88396
• Protein Description: RecName: Full=GrpE protein homolog 2, mitochondrial; AltName: Full=Mt-GrpE#2; Flags: Precursor;
• Gene Information: Name=Grpel2; Synonyms=Mt-grpel2;
• Organism (full): Mus musculus (Mouse).
• Protein Family: Belongs to the GrpE family. .
• Key Domains: GrpE. (IPR000740); GrpE_CC. (IPR013805); GrpE_head. (IPR009012); GrpE (PF01025)

MANDATORY VERIFICATION STEPS:

1. Check if the gene symbol "Grpel2" matches the protein description above
2. Verify the organism is correct: Mus musculus (Mouse).
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 'Grpel2' 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 Grpel2 (gene ID: Grpel2, UniProt: O88396) in mouse.

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.

Research Report: Mouse Grpel2 (UniProt O88396) — functional annotation of mitochondrial GrpE protein homolog 2

0. Target identity verification (critical)

The queried mouse gene Grpel2 encodes a mitochondrial GrpE-family co-chaperone (also referred to in the literature as GRPEL2/GrpE-like 2/mtGrpE2) that functions in the mitochondrial HSP70 (mtHSP70/HSPA9, “mortalin”) chaperone cycle. Across mechanistic and physiological literature, GRPEL2 is consistently discussed as one of two mammalian mitochondrial GrpE-like nucleotide exchange factors (NEFs), with GRPEL1 as the other paralog, and is localized/functioning in the mitochondrial matrix. (konovalova2018redoxregulationof pages 1-2, neupane2022interorganellarandsystemic pages 1-2, manjunath2024preferentialbindingof pages 1-2)

1. Key concepts and definitions (current understanding)

1.1 What GRPEL2 is

GRPEL2 (GrpE-like 2) is a GrpE-family co-chaperone in mammalian mitochondria that is classically annotated as a nucleotide exchange factor (NEF) for mtHSP70/HSPA9, i.e., it helps regulate the ADP↔ATP exchange step that controls HSP70 substrate binding/release. (jadiya2020mitochondrialproteinquality pages 6-8, havalova2021mitochondrialhsp70chaperone pages 6-8)

1.2 Where it acts (subcellular localization)

GRPEL2 is described as mitochondrial and matrix-localized, fitting its role in the mtHSP70 system that mediates matrix-side protein import/folding. Experimental proximity labeling (BioID) and import context place GRPEL2 in the mitochondrial matrix proteostasis environment. (konovalova2018redoxregulationof pages 1-2, konovalova2018redoxregulationof pages 5-6)

1.3 What it does mechanistically in mitochondria

In canonical mtHSP70 cycles, GrpE-like NEFs (GRPEL1/2) assist ADP-for-ATP exchange on mtHSP70, which promotes release of bound substrates/imported precursor proteins and thereby controls the rate of the mtHSP70 folding/import cycle. (havalova2021mitochondrialhsp70chaperone pages 6-8, jadiya2020mitochondrialproteinquality pages 6-8)

1.4 Relationship to GRPEL1 (division of labor)

Multiple lines of evidence support a non-redundant division of labor between the two paralogs:
- GRPEL1 is repeatedly described as the primary/housekeeping NEF required for matrix protein import; loss of GRPEL1 is poorly tolerated and cannot be compensated by GRPEL2 in vivo. (neupane2022interorganellarandsystemic pages 1-2)
- GRPEL2 is described as non-essential under basal conditions in cultured cells, with proposed roles in stress/redox adaptation rather than baseline import. (konovalova2018redoxregulationof pages 2-3, neupane2022interorganellarandsystemic pages 1-2)

2. Recent developments and latest research (prioritizing 2023–2024)

2.1 2024: revised biochemical model—GRPEL1 preferentially binds ADP-mtHSP70, GRPEL2 is weaker and redox-modulated

A 2024 Protein Science study directly compared GRPEL1 vs GRPEL2 interactions with mtHSP70 and found strong biochemical asymmetry:
- ADP-bound mtHSP70 binds GRPEL1 with much higher affinity than GRPEL2, and GRPEL1 (not GRPEL2) promotes the functional conformational opening associated with ADP release in structural models; GRPEL2 lacks key interactions with mtHSP70 NBD region IIB in the modeled complex. (manjunath2024preferentialbindingof pages 9-11)
- In their measurements, GRPEL1 reached KD ~13.4 nM upon ADP addition, while GRPEL2 affinity was reported as ~100-fold lower in the presence of ADP; under non-reducing conditions the study reports KD values around 370 nM (GRPEL1) and 373 nM (GRPEL2) and demonstrates that a GRPEL2-C87A mutant had stronger binding (~203 nM) in that condition (n=3 independent experiments). (manjunath2024preferentialbindingof pages 9-11)
- The study concludes GRPEL1 is the dominant functional NEF for ADP-mtHSP70, while GRPEL2 is best understood as a stress/redox-regulated paralog with reduced effective NEF function under the tested conditions. (manjunath2024preferentialbindingof pages 1-2, manjunath2024preferentialbindingof pages 9-11)

Interpretation: For mouse functional annotation, this work suggests that although GRPEL2 is GrpE-like and historically categorized as an NEF, its biochemical contribution may be conditional (e.g., stress states) and/or mediated through mechanisms other than being the primary ADP-release factor for mtHSP70. (manjunath2024preferentialbindingof pages 1-2, manjunath2024preferentialbindingof pages 9-11)

2.2 2023: mouse disease-model evidence—Grpel2 is protective in diabetic cardiomyopathy by supporting mitochondrial function and DLST import

A 2023 Journal of Translational Medicine study examined Grpel2 in a streptozotocin (STZ)-induced diabetic cardiomyopathy (DCM) mouse model:
- Model and cohorts: Male C57BL/6J mice received STZ (50 mg/kg daily for 5 days); diabetes defined as fasting glucose >11.1 mmol/L; total 108 mice were used across the study. (yang2023grpel2maintainscardiomyocyte pages 1-2)
- Expression change: Grpel2 mRNA and protein were downregulated in diabetic hearts at 6 and 12 weeks post-STZ and decreased in neonatal cardiomyocytes after high-glucose exposure. (yang2023grpel2maintainscardiomyocyte pages 5-7, yang2023grpel2maintainscardiomyocyte media c401b386)
- Intervention/implementation: Cardiac-specific AAV9-Grpel2 (intramyocardial injection; cTnT promoter) increased cardiac Grpel2 and was tested as a proof-of-concept gene therapy approach. (yang2023grpel2maintainscardiomyocyte pages 5-7, yang2023grpel2maintainscardiomyocyte pages 1-2)
- Outcomes (cardiac function, remodeling, survival): AAV9-Grpel2 improved systolic and diastolic parameters and increased survival in the DCM model. The survival cohort was n=16/group and echocardiography cohorts were n=6–8/group, with significance indicated as p<0.05 in reported analyses/figures. (yang2023grpel2maintainscardiomyocyte pages 5-7, yang2023grpel2maintainscardiomyocyte media d054cba9)
- Pressure–volume statistics: An example from Table 1 shows diabetes reduced ESPVR from 23.46 ± 2.39 (control) to 15.54 ± 1.39 (DCM), with partial rescue to 18.79 ± 2.04 (DCM + AAV9-Grpel2), with group comparisons annotated as p<0.05 and #p<0.05. (yang2023grpel2maintainscardiomyocyte pages 7-10, yang2023grpel2maintainscardiomyocyte media c401b386)
- Mitochondrial mechanism/phenotypes: Grpel2 overexpression reduced oxidative stress and mitochondrial dysfunction (e.g., total/mitochondrial ROS), improved mitochondrial morphology and ATP deficiency, and shifted mitochondrial fission/fusion signaling (e.g., increased Opa1; altered phosphorylation of Drp1 at Ser637/Ser616). (yang2023grpel2maintainscardiomyocyte pages 7-10, yang2023grpel2maintainscardiomyocyte media c99fdc5a)
- Mechanistic axis: Grpel2 physically interacted with DLST and increased DLST abundance in mitochondrial lysates under high glucose; DLST knockdown blocked Grpel2’s protective mitochondrial and survival effects. (yang2023grpel2maintainscardiomyocyte pages 14-16, yang2023grpel2maintainscardiomyocyte pages 10-14)
- Transcriptional regulation: Nr2f6* bound the Grpel2 promoter and positively regulated Grpel2 expression in their system. (yang2023grpel2maintainscardiomyocyte pages 14-16, yang2023grpel2maintainscardiomyocyte pages 19-20)

Interpretation: In mouse heart under diabetic stress, Grpel2 appears to be a mitochondrial homeostasis factor whose augmentation improves disease phenotypes, consistent with a stress-adaptive function for GRPEL2 rather than strict housekeeping import. (yang2023grpel2maintainscardiomyocyte pages 14-16, yang2023grpel2maintainscardiomyocyte pages 7-10)

3. Pathways and biological processes (with evidence)

3.1 Mitochondrial protein import and matrix proteostasis (PAM/mtHSP70 cycle)

GRPEL2 is functionally situated within the mtHSP70 chaperone system that drives nuclear-encoded protein import and matrix folding. Reviews describe GrpE-like proteins (GRPEL1/2) as NEFs that drive ADP→ATP exchange on mortalin/mtHSP70, promoting release of imported precursors and regulating the cycle rate. (havalova2021mitochondrialhsp70chaperone pages 6-8)

A mitochondrial protein quality control review similarly frames GRPEL proteins (including GRPEL2) as GrpE-family NEFs that initiate substrate release by stimulating ADP-for-ATP exchange on mtHSP70, linking GRPEL2 to TOM/TIM-associated translocation and import/folding processes. (jadiya2020mitochondrialproteinquality pages 6-8)

3.2 Redox/stress regulation of GRPEL2

A central mechanistic theme is that GRPEL2 is redox-sensitive:
- Oxidative stress (e.g., H2O2) induces GRPEL2 disulfide-linked dimerization via Cys87; C87A abrogates this response, supporting a thiol-switch model. (konovalova2018redoxregulationof pages 2-3, konovalova2018redoxregulationof pages 6-7)
- GRPEL2 redox regulation is emphasized as specific to GRPEL2 (GRPEL1 lacks comparable cysteines enabling analogous disulfide bridging) and proposed to connect mitochondrial redox state to matrix protein import/folding demands. (konovalova2018redoxregulationof pages 6-7)

The 2024 biochemical study further supports that GRPEL2’s cysteine chemistry can modulate mtHSP70 binding behavior (e.g., in non-reducing conditions, C87A shows higher affinity). (manjunath2024preferentialbindingof pages 9-11)

3.3 In vivo essentiality contrasts (GRPEL1 essential, GRPEL2 non-compensatory)

In a mouse skeletal muscle model, deletion of Grpel1 produced severe mitochondrial import dysfunction and systemic responses, and the authors explicitly frame mammalian mitochondria as containing two GrpE-like NEFs (GRPEL1/2) while concluding that GRPEL1 is essential and cannot be compensated by GRPEL2 in vivo. (neupane2022interorganellarandsystemic pages 1-2)

4. Current applications and real-world implementations

4.1 Gene therapy-style augmentation of Grpel2 in cardiovascular disease models

A concrete implementation is AAV9-mediated cardiac delivery of Grpel2 in STZ-induced diabetic cardiomyopathy, where Grpel2 overexpression improved survival and cardiac function and reduced remodeling/mitochondrial dysfunction (proof-of-concept therapeutic strategy). (yang2023grpel2maintainscardiomyocyte pages 5-7, yang2023grpel2maintainscardiomyocyte media d054cba9, yang2023grpel2maintainscardiomyocyte pages 7-10)

4.2 GRPEL2 as a disease-associated marker/target in glioma datasets and GBM cell models

In glioblastoma and glioma cohort data (TCGA/CGGA), higher GRPEL2 expression correlated with worse clinical features:
- GRPEL2 expression increased with WHO grade (TCGA Grade II n=225; III n=272; IV n=165), and high-expression groups had shorter survival (TCGA p<0.001; CGGA p=0.013 and p=0.009 across datasets). (tang2021grpel2knockdownexerts pages 2-4)
- A tissue microarray study (95 samples) showed higher GRPEL2 staining associated with higher grade (p<0.05). (tang2021grpel2knockdownexerts pages 2-4)

Functionally, siRNA knockdown of GRPEL2 in GBM cell lines inhibited proliferation and reduced oxygen consumption rate (OCR), consistent with a role in mitochondrial bioenergetics/redox state in that context. (tang2021grpel2knockdownexerts pages 1-2)

5. Expert opinions and analysis (authoritative synthesis)

5.1 Consensus view from reviews (2020–2021)

Authoritative reviews position GRPEL2 in a conserved mtHSP70 co-chaperone network, with GRPEL proteins serving as NEFs that drive mtHSP70 nucleotide exchange and thereby control substrate release and precursor handling in mitochondria. (havalova2021mitochondrialhsp70chaperone pages 6-8, jadiya2020mitochondrialproteinquality pages 6-8)

5.2 Mechanistic refinement from recent primary research

A key expert-level refinement is the emerging view that GRPEL1 and GRPEL2 are not equivalent NEFs. Recent biochemical/structural results support GRPEL1 as the dominant ADP-mtHSP70 interactor/functional NEF, while GRPEL2’s role is more compatible with redox/stress tuning and potentially alternative modes of regulating mitochondrial proteostasis. (manjunath2024preferentialbindingof pages 1-2, manjunath2024preferentialbindingof pages 9-11)

6. Statistics and data highlights from recent studies

• Diabetic cardiomyopathy (mouse, 2023): Total mice n=108; survival cohort n=16/group; echo cohorts n=6–8/group; example pressure-volume statistic: ESPVR 23.46 ± 2.39 (control) vs 15.54 ± 1.39 (DCM) vs 18.79 ± 2.04 (DCM + AAV9-Grpel2) with *p<0.05/#p<0.05 per study annotation. (yang2023grpel2maintainscardiomyocyte pages 1-2, yang2023grpel2maintainscardiomyocyte pages 5-7, yang2023grpel2maintainscardiomyocyte pages 7-10)
• mtHSP70 binding biophysics (2024): ADP addition yielded GRPEL1 KD ~13.4 nM; GRPEL2 affinity in presence of ADP was reported ~100-fold lower; in non-reducing conditions KD values reported include ~370 nM (GRPEL1), ~373 nM (GRPEL2), ~203 nM (GRPEL2-C87A) (n=3). (manjunath2024preferentialbindingof pages 9-11)
• Glioma prognosis associations (2021): High-GRPEL2 expression associated with shorter survival (TCGA p<0.001; CGGA p=0.013 and p=0.009) with large cohorts and clear group sizes; strong correlation with TERT expression reported (r=0.705; n=688; p=1.52×10−104). (tang2021grpel2knockdownexerts pages 2-4, tang2021grpel2knockdownexerts pages 4-6)

7. Limitations and evidence gaps (important for annotation)

• Direct mouse Grpel2 loss-of-function phenotyping (knockout) in normal physiology is not represented in the retrieved primary evidence set; much of the strong in vivo essentiality evidence pertains to GRPEL1, with GRPEL2 inferred as non-compensatory/stress-associated. (neupane2022interorganellarandsystemic pages 1-2)
• Quantitative values for some functional readouts (e.g., exact LVEF/LVFS means) were present in figures but not fully extractable from text alone; the study’s figure panels directly show improvement with AAV9-Grpel2. (yang2023grpel2maintainscardiomyocyte media d054cba9, yang2023grpel2maintainscardiomyocyte media c401b386)

8. Practical functional annotation summary (mouse Grpel2, UniProt O88396)

Recommended functional annotation (evidence-based):
- Molecular function: GrpE-family co-chaperone associated with the mtHSP70 system; historically annotated as a nucleotide exchange factor promoting ADP→ATP exchange on mtHSP70; recent biochemical evidence suggests reduced/conditional NEF activity relative to GRPEL1 and strong redox/stress modulation. (havalova2021mitochondrialhsp70chaperone pages 6-8, jadiya2020mitochondrialproteinquality pages 6-8, manjunath2024preferentialbindingof pages 9-11)
- Biological process: Mitochondrial matrix proteostasis including protein import/folding (PAM/mtHSP70 cycle) and oxidative stress-responsive regulation of chaperone activity. (havalova2021mitochondrialhsp70chaperone pages 6-8, konovalova2018redoxregulationof pages 6-7)
- Cellular component: Mitochondrial matrix (site of mtHSP70-driven import/folding and GRPEL2 proximity). (konovalova2018redoxregulationof pages 1-2)
- Pathway connections (experimentally supported in disease model): In diabetic cardiomyopathy, Grpel2 supports mitochondrial function and cardiomyocyte survival via an axis involving DLST mitochondrial import/localization and transcriptional regulation by Nr2f6. (yang2023grpel2maintainscardiomyocyte pages 14-16, yang2023grpel2maintainscardiomyocyte pages 19-20)

Summary table of key sources

The following table consolidates the most relevant studies (prioritizing 2023–2024) with findings, quantitative highlights, and URLs.

Table: This table summarizes the most relevant studies for functional annotation of mouse Grpel2/GRPEL2, emphasizing recent 2023-2024 work while anchoring interpretation in foundational mechanistic and review papers. It highlights system context, core mechanistic conclusions, quantitative details, methods, and publication metadata.

References

1. (konovalova2018redoxregulationof pages 1-2): Svetlana Konovalova, Xiaonan Liu, Pooja Manjunath, Sundar Baral, Nirajan Neupane, Taru Hilander, Yang Yang, Diego Balboa, Mügen Terzioglu, Liliya Euro, Markku Varjosalo, and Henna Tyynismaa. Redox regulation of grpel2 nucleotide exchange factor for mitochondrial hsp70 chaperone. Redox Biology, 19:37-45, Oct 2018. URL: https://doi.org/10.1016/j.redox.2018.07.024, doi:10.1016/j.redox.2018.07.024. This article has 45 citations and is from a domain leading peer-reviewed journal.

2. (neupane2022interorganellarandsystemic pages 1-2): Nirajan Neupane, Jayasimman Rajendran, Jouni Kvist, Sandra Harjuhaahto, Bowen Hu, Veijo Kinnunen, Yang Yang, Anni I. Nieminen, and Henna Tyynismaa. Inter-organellar and systemic responses to impaired mitochondrial matrix protein import in skeletal muscle. Communications Biology, Oct 2022. URL: https://doi.org/10.1038/s42003-022-04034-z, doi:10.1038/s42003-022-04034-z. This article has 25 citations and is from a peer-reviewed journal.

3. (manjunath2024preferentialbindingof pages 1-2): Pooja Manjunath, Gorazd Stojkovič, Liliya Euro, Svetlana Konovalova, Sjoerd Wanrooij, Kristian Koski, and Henna Tyynismaa. Preferential binding of adp‐bound mitochondrial hsp70 to the nucleotide exchange factor grpel1 over grpel2. Protein Science, Oct 2024. URL: https://doi.org/10.1002/pro.5190, doi:10.1002/pro.5190. This article has 7 citations and is from a peer-reviewed journal.

4. (jadiya2020mitochondrialproteinquality pages 6-8): Pooja Jadiya and Dhanendra Tomar. Mitochondrial protein quality control mechanisms. Genes, 11:563, May 2020. URL: https://doi.org/10.3390/genes11050563, doi:10.3390/genes11050563. This article has 103 citations.

5. (havalova2021mitochondrialhsp70chaperone pages 6-8): Henrieta Havalová, Gabriela Ondrovičová, Barbora Keresztesová, Jacob A. Bauer, Vladimír Pevala, Eva Kutejová, and Nina Kunová. Mitochondrial hsp70 chaperone system—the influence of post-translational modifications and involvement in human diseases. International Journal of Molecular Sciences, 22:8077, Jul 2021. URL: https://doi.org/10.3390/ijms22158077, doi:10.3390/ijms22158077. This article has 74 citations.

6. (konovalova2018redoxregulationof pages 5-6): Svetlana Konovalova, Xiaonan Liu, Pooja Manjunath, Sundar Baral, Nirajan Neupane, Taru Hilander, Yang Yang, Diego Balboa, Mügen Terzioglu, Liliya Euro, Markku Varjosalo, and Henna Tyynismaa. Redox regulation of grpel2 nucleotide exchange factor for mitochondrial hsp70 chaperone. Redox Biology, 19:37-45, Oct 2018. URL: https://doi.org/10.1016/j.redox.2018.07.024, doi:10.1016/j.redox.2018.07.024. This article has 45 citations and is from a domain leading peer-reviewed journal.

7. (konovalova2018redoxregulationof pages 2-3): Svetlana Konovalova, Xiaonan Liu, Pooja Manjunath, Sundar Baral, Nirajan Neupane, Taru Hilander, Yang Yang, Diego Balboa, Mügen Terzioglu, Liliya Euro, Markku Varjosalo, and Henna Tyynismaa. Redox regulation of grpel2 nucleotide exchange factor for mitochondrial hsp70 chaperone. Redox Biology, 19:37-45, Oct 2018. URL: https://doi.org/10.1016/j.redox.2018.07.024, doi:10.1016/j.redox.2018.07.024. This article has 45 citations and is from a domain leading peer-reviewed journal.

8. (manjunath2024preferentialbindingof pages 9-11): Pooja Manjunath, Gorazd Stojkovič, Liliya Euro, Svetlana Konovalova, Sjoerd Wanrooij, Kristian Koski, and Henna Tyynismaa. Preferential binding of adp‐bound mitochondrial hsp70 to the nucleotide exchange factor grpel1 over grpel2. Protein Science, Oct 2024. URL: https://doi.org/10.1002/pro.5190, doi:10.1002/pro.5190. This article has 7 citations and is from a peer-reviewed journal.

9. (yang2023grpel2maintainscardiomyocyte pages 1-2): Rongjin Yang, Xiaomeng Zhang, Yunyun Zhang, Yingfan Wang, Man Li, Yuancui Meng, Jianbang Wang, Xue Wen, Jun Yu, and Pan Chang. Grpel2 maintains cardiomyocyte survival in diabetic cardiomyopathy through dlst-mediated mitochondrial dysfunction: a proof-of-concept study. Journal of Translational Medicine, Mar 2023. URL: https://doi.org/10.1186/s12967-023-04049-y, doi:10.1186/s12967-023-04049-y. This article has 9 citations and is from a peer-reviewed journal.

10. (yang2023grpel2maintainscardiomyocyte pages 5-7): Rongjin Yang, Xiaomeng Zhang, Yunyun Zhang, Yingfan Wang, Man Li, Yuancui Meng, Jianbang Wang, Xue Wen, Jun Yu, and Pan Chang. Grpel2 maintains cardiomyocyte survival in diabetic cardiomyopathy through dlst-mediated mitochondrial dysfunction: a proof-of-concept study. Journal of Translational Medicine, Mar 2023. URL: https://doi.org/10.1186/s12967-023-04049-y, doi:10.1186/s12967-023-04049-y. This article has 9 citations and is from a peer-reviewed journal.

11. (yang2023grpel2maintainscardiomyocyte media c401b386): Rongjin Yang, Xiaomeng Zhang, Yunyun Zhang, Yingfan Wang, Man Li, Yuancui Meng, Jianbang Wang, Xue Wen, Jun Yu, and Pan Chang. Grpel2 maintains cardiomyocyte survival in diabetic cardiomyopathy through dlst-mediated mitochondrial dysfunction: a proof-of-concept study. Journal of Translational Medicine, Mar 2023. URL: https://doi.org/10.1186/s12967-023-04049-y, doi:10.1186/s12967-023-04049-y. This article has 9 citations and is from a peer-reviewed journal.

12. (yang2023grpel2maintainscardiomyocyte media d054cba9): Rongjin Yang, Xiaomeng Zhang, Yunyun Zhang, Yingfan Wang, Man Li, Yuancui Meng, Jianbang Wang, Xue Wen, Jun Yu, and Pan Chang. Grpel2 maintains cardiomyocyte survival in diabetic cardiomyopathy through dlst-mediated mitochondrial dysfunction: a proof-of-concept study. Journal of Translational Medicine, Mar 2023. URL: https://doi.org/10.1186/s12967-023-04049-y, doi:10.1186/s12967-023-04049-y. This article has 9 citations and is from a peer-reviewed journal.

13. (yang2023grpel2maintainscardiomyocyte pages 7-10): Rongjin Yang, Xiaomeng Zhang, Yunyun Zhang, Yingfan Wang, Man Li, Yuancui Meng, Jianbang Wang, Xue Wen, Jun Yu, and Pan Chang. Grpel2 maintains cardiomyocyte survival in diabetic cardiomyopathy through dlst-mediated mitochondrial dysfunction: a proof-of-concept study. Journal of Translational Medicine, Mar 2023. URL: https://doi.org/10.1186/s12967-023-04049-y, doi:10.1186/s12967-023-04049-y. This article has 9 citations and is from a peer-reviewed journal.

14. (yang2023grpel2maintainscardiomyocyte media c99fdc5a): Rongjin Yang, Xiaomeng Zhang, Yunyun Zhang, Yingfan Wang, Man Li, Yuancui Meng, Jianbang Wang, Xue Wen, Jun Yu, and Pan Chang. Grpel2 maintains cardiomyocyte survival in diabetic cardiomyopathy through dlst-mediated mitochondrial dysfunction: a proof-of-concept study. Journal of Translational Medicine, Mar 2023. URL: https://doi.org/10.1186/s12967-023-04049-y, doi:10.1186/s12967-023-04049-y. This article has 9 citations and is from a peer-reviewed journal.

15. (yang2023grpel2maintainscardiomyocyte pages 14-16): Rongjin Yang, Xiaomeng Zhang, Yunyun Zhang, Yingfan Wang, Man Li, Yuancui Meng, Jianbang Wang, Xue Wen, Jun Yu, and Pan Chang. Grpel2 maintains cardiomyocyte survival in diabetic cardiomyopathy through dlst-mediated mitochondrial dysfunction: a proof-of-concept study. Journal of Translational Medicine, Mar 2023. URL: https://doi.org/10.1186/s12967-023-04049-y, doi:10.1186/s12967-023-04049-y. This article has 9 citations and is from a peer-reviewed journal.

16. (yang2023grpel2maintainscardiomyocyte pages 10-14): Rongjin Yang, Xiaomeng Zhang, Yunyun Zhang, Yingfan Wang, Man Li, Yuancui Meng, Jianbang Wang, Xue Wen, Jun Yu, and Pan Chang. Grpel2 maintains cardiomyocyte survival in diabetic cardiomyopathy through dlst-mediated mitochondrial dysfunction: a proof-of-concept study. Journal of Translational Medicine, Mar 2023. URL: https://doi.org/10.1186/s12967-023-04049-y, doi:10.1186/s12967-023-04049-y. This article has 9 citations and is from a peer-reviewed journal.

17. (yang2023grpel2maintainscardiomyocyte pages 19-20): Rongjin Yang, Xiaomeng Zhang, Yunyun Zhang, Yingfan Wang, Man Li, Yuancui Meng, Jianbang Wang, Xue Wen, Jun Yu, and Pan Chang. Grpel2 maintains cardiomyocyte survival in diabetic cardiomyopathy through dlst-mediated mitochondrial dysfunction: a proof-of-concept study. Journal of Translational Medicine, Mar 2023. URL: https://doi.org/10.1186/s12967-023-04049-y, doi:10.1186/s12967-023-04049-y. This article has 9 citations and is from a peer-reviewed journal.

18. (konovalova2018redoxregulationof pages 6-7): Svetlana Konovalova, Xiaonan Liu, Pooja Manjunath, Sundar Baral, Nirajan Neupane, Taru Hilander, Yang Yang, Diego Balboa, Mügen Terzioglu, Liliya Euro, Markku Varjosalo, and Henna Tyynismaa. Redox regulation of grpel2 nucleotide exchange factor for mitochondrial hsp70 chaperone. Redox Biology, 19:37-45, Oct 2018. URL: https://doi.org/10.1016/j.redox.2018.07.024, doi:10.1016/j.redox.2018.07.024. This article has 45 citations and is from a domain leading peer-reviewed journal.

19. (tang2021grpel2knockdownexerts pages 2-4): Chi-Tun Tang, Yao-Feng Li, Chung-Hsing Chou, Li-Chun Huang, Shih-Ming Huang, Dueng-Yuan Hueng, Chia-Kuang Tsai, and Yuan-Hao Chen. Grpel2 knockdown exerts redox regulation in glioblastoma. International Journal of Molecular Sciences, 22:12705, Nov 2021. URL: https://doi.org/10.3390/ijms222312705, doi:10.3390/ijms222312705. This article has 13 citations.

20. (tang2021grpel2knockdownexerts pages 1-2): Chi-Tun Tang, Yao-Feng Li, Chung-Hsing Chou, Li-Chun Huang, Shih-Ming Huang, Dueng-Yuan Hueng, Chia-Kuang Tsai, and Yuan-Hao Chen. Grpel2 knockdown exerts redox regulation in glioblastoma. International Journal of Molecular Sciences, 22:12705, Nov 2021. URL: https://doi.org/10.3390/ijms222312705, doi:10.3390/ijms222312705. This article has 13 citations.

21. (tang2021grpel2knockdownexerts pages 4-6): Chi-Tun Tang, Yao-Feng Li, Chung-Hsing Chou, Li-Chun Huang, Shih-Ming Huang, Dueng-Yuan Hueng, Chia-Kuang Tsai, and Yuan-Hao Chen. Grpel2 knockdown exerts redox regulation in glioblastoma. International Journal of Molecular Sciences, 22:12705, Nov 2021. URL: https://doi.org/10.3390/ijms222312705, doi:10.3390/ijms222312705. This article has 13 citations.

22. (manjunath2024preferentialbindingof pages 12-13): Pooja Manjunath, Gorazd Stojkovič, Liliya Euro, Svetlana Konovalova, Sjoerd Wanrooij, Kristian Koski, and Henna Tyynismaa. Preferential binding of adp‐bound mitochondrial hsp70 to the nucleotide exchange factor grpel1 over grpel2. Protein Science, Oct 2024. URL: https://doi.org/10.1002/pro.5190, doi:10.1002/pro.5190. This article has 7 citations and is from a peer-reviewed journal.

Citations

1. neupane2022interorganellarandsystemic pages 1-2
2. manjunath2024preferentialbindingof pages 9-11
3. jadiya2020mitochondrialproteinquality pages 6-8
4. konovalova2018redoxregulationof pages 6-7
5. konovalova2018redoxregulationof pages 1-2
6. manjunath2024preferentialbindingof pages 1-2
7. konovalova2018redoxregulationof pages 5-6
8. konovalova2018redoxregulationof pages 2-3
9. manjunath2024preferentialbindingof pages 12-13
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Grpel2 curation notes

Deep research status: just deep-research-falcon mouse Grpel2 --fallback perplexity-lite --timeout 60 was first run on 2026-05-03. Falcon timed out, and the requested perplexity-lite fallback failed with a 401 insufficient-quota error. Per course correction, just deep-research-falcon mouse Grpel2 --timeout 1800 --fallback perplexity-lite was then run one gene at a time and succeeded, producing Grpel2-deep-research-falcon.md.

Core evidence: Grpel2 is a mitochondrial GrpE-family nucleotide exchange factor for mitochondrial Hsp70/HSPA9 and a component of the PAM import motor. The core molecular function is adenyl-nucleotide exchange factor activity, not direct unfolded-substrate binding.

Falcon synthesis: The Falcon report verifies GRPEL2 as a mitochondrial matrix GrpE-family co-chaperone in the mtHSP70/HSPA9 system. It adds an important paralog-specific nuance: recent biochemical work supports GRPEL1 as the dominant housekeeping NEF for ADP-bound mtHSP70, while GRPEL2 appears weaker and more redox/stress-modulated, with conditional roles in mitochondrial matrix proteostasis and disease/stress models such as diabetic cardiomyopathy [file:mouse/Grpel2/Grpel2-deep-research-falcon.md].

Experimental evidence: Naylor et al. report that the mammalian mitochondrial GrpE-like proteins "specifically interact with and stimulate the ATPase activity of mammalian mitochondrial Hsp70 (mt-Hsp70)" PMID:9694873. This supports nucleotide-exchange/co-chaperone activity and Hsp70/chaperone binding.

Localization evidence: UniProt annotates Grpel2 as mitochondrial matrix localized and describes a mitochondrial transit peptide; mitochondrial proteomics annotations are supporting but less specific than the matrix/PAM-complex biology.

Curation rule: GO:0051082 unfolded protein binding should be modified for Grpel2 because GrpE is a nucleotide exchange factor for Hsp70 rather than a direct unfolded substrate-binding chaperone. GO:0044183 protein folding chaperone is a better replacement for the co-chaperone role.