| Category | Evidence summary | Key sources (year, journal, URL, context ids) |
|---|---|---|
| Identity/domains | Human BAG2 corresponds to BCL2-associated athanogene 2 / BAG family molecular chaperone regulator 2, a BAG-family co-chaperone identified in CHIP-containing complexes. Retrieved evidence supports a C-terminal BAG domain that binds the ATPase domain of Hsc70/Hsp70 and an N-terminal coiled-coil region that mediates homodimerization; BAG2 lacks the ubiquitin-like domain present in BAG1. Retrieved excerpts did not explicitly state UniProt O95816, but the protein identity, BAG-domain architecture, and human-cell context align with the requested target. (pqac-00000009, pqac-00000010, pqac-00000011, pqac-00000012, pqac-00000013) | Arndt et al., 2005, *Molecular Biology of the Cell*, https://doi.org/10.1091/mbc.e05-07-0660 (pqac-00000009, pqac-00000010, pqac-00000011); Schönbühler et al., 2016, *International Journal of Molecular Sciences*, https://doi.org/10.3390/ijms18010069 (pqac-00000012); Heymann, 2019, thesis/article excerpt, no journal metadata in excerpt (pqac-00000013) |
| Molecular function | BAG2 functions as an HSP70/HSC70 co-chaperone and nucleotide-exchange factor, promoting ADP/ATP exchange on HSP70-family chaperones. A core experimentally supported role is inhibition of CHIP/STUB1 E3 ligase activity, including disruption of CHIP–E2 cooperation and suppression of CHIP-mediated ubiquitination of HSP72 and Raf-1; BAG2 can also bind misfolded proteins and reduce aggregation, shifting protein triage toward stabilization/folding rather than degradation. (pqac-00000002, pqac-00000003, pqac-00000004, pqac-00000006, pqac-00000008, pqac-00000021) | Arndt et al., 2005, *Molecular Biology of the Cell*, https://doi.org/10.1091/mbc.e05-07-0660 (pqac-00000004, pqac-00000021); Schönbühler et al., 2016, *International Journal of Molecular Sciences*, https://doi.org/10.3390/ijms18010069 (pqac-00000002, pqac-00000003, pqac-00000006); Altinok et al., 2021, *Cells*, https://doi.org/10.3390/cells10113121 (pqac-00000008) |
| Key partners/clients | Strongest supported partners are Hsc70/Hsp70 family chaperones and CHIP/STUB1. BAG2 forms ternary complexes with Hsc70/Hsp70 and CHIP, and reported clients/substrates modulated through this axis include HSP72, Hsc70, Raf-1, CFTR maturation machinery, and in newer cancer studies HSP70/Apaf1/Cytochrome c signaling components. In fibrolamellar carcinoma, BAG2 recruitment to DNAJ-PKAc scaffolds is Hsp70-dependent; in gastric cancer, BAG2 forms a BAG2–CHIP–HSP70 complex affecting Apaf1/Cyt c apoptosis signaling. (pqac-00000003, pqac-00000004, pqac-00000005, pqac-00000007, pqac-00000010, pqac-00000023, pqac-00000026) | Arndt et al., 2005, *Molecular Biology of the Cell*, https://doi.org/10.1091/mbc.e05-07-0660 (pqac-00000004, pqac-00000010); Schönbühler et al., 2016, *International Journal of Molecular Sciences*, https://doi.org/10.3390/ijms18010069 (pqac-00000003); Liu et al., 2024, Research Square preprint, https://doi.org/10.21203/rs.3.rs-4285523/v1 (pqac-00000005); Lauer et al., 2024, *bioRxiv*, https://doi.org/10.1101/2023.06.28.546958 (pqac-00000007, pqac-00000023, pqac-00000026) |
| Pathways | BAG2 is most strongly linked to proteostasis/protein quality control, especially the HSP70/HSC70–CHIP axis and ubiquitin-proteasome triage. Evidence also connects BAG2 to chaperone-assisted maturation of CFTR, aging-associated proteostasis changes, mitochondrial/intrinsic apoptosis through HSP70–Apaf1–cytochrome c signaling in gastric cancer, and Hsp70-linked pro-survival scaffolding in fibrolamellar carcinoma. Retrieved excerpts mention autophagy as a CHIP-related context, but direct BAG2-specific autophagy/mitophagy evidence was limited in the retrieved texts. Innate-immunity regulation was not directly supported by the gathered excerpts. (pqac-00000001, pqac-00000003, pqac-00000005, pqac-00000006, pqac-00000011, pqac-00000024, pqac-00000026) | Arndt et al., 2005, *Molecular Biology of the Cell*, https://doi.org/10.1091/mbc.e05-07-0660 (pqac-00000011); Schönbühler et al., 2016, *International Journal of Molecular Sciences*, https://doi.org/10.3390/ijms18010069 (pqac-00000003, pqac-00000006); Liu et al., 2024, Research Square preprint, https://doi.org/10.21203/rs.3.rs-4285523/v1 (pqac-00000001, pqac-00000005); Lauer et al., 2024, *bioRxiv*, https://doi.org/10.1101/2023.06.28.546958 (pqac-00000024, pqac-00000026) |
| Localization/complexes | Retrieved evidence supports BAG2 existing in large cytosolic/high-molecular-mass protein complexes with Hsc70 and CHIP (reported by gel filtration and immunoprecipitation), and suggests BAG2 may recruit the Hsc70/CHIP machinery to distinct protein complexes or subcellular structures. In DNAJ-PKAc models, BAG2 is recruited into Hsp70-dependent signaling scaffolds. However, precise steady-state subcellular localization was not well specified in the retrieved excerpts and should be treated as incompletely resolved here. (pqac-00000004, pqac-00000010, pqac-00000021, pqac-00000023, pqac-00000027) | Arndt et al., 2005, *Molecular Biology of the Cell*, https://doi.org/10.1091/mbc.e05-07-0660 (pqac-00000004, pqac-00000010, pqac-00000021); Lauer et al., 2024, *bioRxiv*, https://doi.org/10.1101/2023.06.28.546958 (pqac-00000023, pqac-00000027) |
| 2023-2024 developments | Recent studies expand BAG2 beyond classical proteostasis: a 2023 AD network study linked BAG2-HSC70-STUB1-MAPT expression patterns to Alzheimer’s disease progression; 2024 studies implicated BAG2 as a prognostic/functional driver candidate in liposarcoma and malignant pleural mesothelioma, a pro-survival factor recruited to DNAJ-PKAc/Hsp70 scaffolds in fibrolamellar carcinoma, and an oncogenic regulator of the BAG2–CHIP–HSP70 axis in gastric cancer. These newer reports are more disease-contextual than foundational mechanistic studies but consistently reinforce BAG2 as a regulator of chaperone-dependent protein triage and apoptosis resistance. (pqac-00000005, pqac-00000014, pqac-00000015, pqac-00000017, pqac-00000018, pqac-00000023, pqac-00000024, pqac-00000026) | Yang et al., 2023, *Frontiers in Aging Neuroscience*, https://doi.org/10.3389/fnagi.2023.1090400 (pqac-00000000); Lian et al., 2024, *Scientific Reports*, https://doi.org/10.1038/s41598-024-67659-6 (pqac-00000014); Bisceglia et al., 2024, *Cancer Gene Therapy*, https://doi.org/10.1038/s41417-024-00805-4 (pqac-00000017, pqac-00000018); Liu et al., 2024, Research Square preprint, https://doi.org/10.21203/rs.3.rs-4285523/v1 (pqac-00000015); Lauer et al., 2024, *bioRxiv*, https://doi.org/10.1101/2023.06.28.546958 (pqac-00000023, pqac-00000024, pqac-00000026) |
| Applications/biomarker/therapeutics | BAG2 is being explored as a biomarker and possible therapeutic target, particularly in cancers. In mesothelioma, BAG2 overexpression by IHC may help distinguish malignant pleural mesothelioma from reactive mesothelial proliferation. In liposarcoma, high BAG2 contributed to a 2-gene risk signature with BAG1. In gastric cancer, the BAG2–CHIP interaction was proposed as a druggable axis, with FIIN-2 reported as a small-molecule inhibitor of the BAG2–CHIP complex in preclinical models. In fibrolamellar carcinoma, BAG2 was proposed as a progression biomarker and chemoresistance factor linked to response to etoposide/navitoclax combinations. No approved BAG2-targeted therapies were identified in the gathered evidence. (pqac-00000001, pqac-00000014, pqac-00000018, pqac-00000020, pqac-00000024, pqac-00000025) | Bisceglia et al., 2024, *Cancer Gene Therapy*, https://doi.org/10.1038/s41417-024-00805-4 (pqac-00000018, pqac-00000020); Lian et al., 2024, *Scientific Reports*, https://doi.org/10.1038/s41598-024-67659-6 (pqac-00000014); Liu et al., 2024, Research Square preprint, https://doi.org/10.21203/rs.3.rs-4285523/v1 (pqac-00000001); Lauer et al., 2024, *bioRxiv*, https://doi.org/10.1101/2023.06.28.546958 (pqac-00000024, pqac-00000025) |
| Quantitative data highlights | Mesothelioma: independent RNA-seq validation cohort n=211; BAG2 upregulated with baseMean 1405.02, log2FC 1.55, lfcSE 0.45, stat 3.47, padj 0.0019; separate tissue cohort n=40 and BAG2 IHC showed moderate/strong staining in MPM but not RMP. Gastric cancer: TCGA RNA analysis n=392 and tissue microarray n=152 paired tumors/adjacent tissues showed BAG2 overexpression associated with poorer prognosis; BAG2 knockout reduced tumor growth and increased apoptotic markers. Fibrolamellar carcinoma: proximity proteomics identified 1,174 proteins with 261 significant interactors; combined etoposide+navitoclax reduced viability in AML12 DNAJ-PKAc cells to 0.450 ± 0.042 versus etoposide and 0.163 ± 0.012 versus vehicle (SEM, n=3). Liposarcoma: BAG2 correlated negatively with PPARG (r=-0.63, p<2.2×10−16) and positively with NFKB1 (r=0.5, p=3.1×10−10). (pqac-00000014, pqac-00000015, pqac-00000017, pqac-00000020, pqac-00000026, pqac-00000027) | Bisceglia et al., 2024, *Cancer Gene Therapy*, https://doi.org/10.1038/s41417-024-00805-4 (pqac-00000017, pqac-00000020); Liu et al., 2024, Research Square preprint, https://doi.org/10.21203/rs.3.rs-4285523/v1 (pqac-00000015); Lauer et al., 2024, *bioRxiv*, https://doi.org/10.1101/2023.06.28.546958 (pqac-00000026, pqac-00000027); Lian et al., 2024, *Scientific Reports*, https://doi.org/10.1038/s41598-024-67659-6 (pqac-00000014) |


*Table: This table summarizes the experimentally supported functional annotation of human BAG2, emphasizing its co-chaperone role in HSP70/HSC70–CHIP proteostasis networks, disease-linked 2023–2024 findings, and quantitative highlights. It is useful as a compact evidence map for identity, mechanism, pathways, localization limits, and translational relevance.*