| Category | Summary |
|---|---|
| Identity/Structure | - Mouse **Hspa8/HSC70 (Hsc73)** is the constitutive cytosolic HSP70-family paralog, distinct from stress-inducible HSP70s.<br>- Domain architecture: **N-terminal ATPase/NBD**, **C-terminal substrate-binding domain (SBD)** with lid, interdomain linker, and **EEVD-containing tail** for cofactor interactions.<br>- Functional annotation is consistent with an HSP70-family housekeeping chaperone/proteostasis factor (pqac-00000000, pqac-00000001) |
| Enzymatic activity | - **ATPase-driven molecular chaperone**: ATP binding/hydrolysis in the NBD controls client capture and release.<br>- ADP-bound state has high substrate affinity in CMA-related binding cycles.<br>- Also functions in ATP-coupled clathrin coat remodeling/uncoating (pqac-00000002, pqac-00000006, pqac-00000021) |
| Substrate recognition | - Binds exposed **hydrophobic peptide segments** typical of non-native proteins.<br>- In **chaperone-mediated autophagy (CMA)**, recognizes **KFERQ-like motifs** and delivers substrates to lysosomes.<br>- 2024 mechanistic evidence highlighted direct HSC70 interaction with KFERQ-like motifs in CMA/microautophagy context (pqac-00000002, pqac-00000005, pqac-00000009) |
| Key co-chaperones | - **J-domain proteins/HSP40s** stimulate ATP hydrolysis and client handoff.<br>- **NEFs** (e.g., BAG family, HSP110 class) promote ADP→ATP exchange.<br>- In CMA/endocytosis contexts, reported partners include **Hip, Hsp40, Hsp90, BAG proteins, GAK, auxilin** (pqac-00000000, pqac-00000002, pqac-00000004, pqac-00000021) |
| Major pathways | - Core **proteostasis/PQC**: folding, refolding, anti-aggregation, routing clients toward degradation.<br>- **CMA**: HSC70 binds KFERQ-bearing substrates, docks at **LAMP2A**, and supports unfolding/translocation.<br>- **Clathrin-mediated endocytosis/synaptic vesicle recycling**: HSC70 works with **GAK/auxilin** to uncoat clathrin-coated vesicles (pqac-00000002, pqac-00000005, pqac-00000021, pqac-00000025) |
| Localization | - Predominantly **cytosolic**, but functionally engages **lysosomal membranes/lumen-associated CMA machinery**.<br>- Also implicated at **endocytic/synaptic vesicle coats** and in **neuronal dendrites** via local Hspa8 mRNA translation.<br>- Broader HSP70 literature supports extracellular/endolysosomal/exosomal trafficking, though HSPA8-specific extracellular evidence here is more limited than for total eHSP70 (pqac-00000002, pqac-00000009, pqac-00000013, pqac-00000018) |
| 2023-2024 developments | - 2023–2024 CMA reviews emphasize HSC70 as the **central substrate-recognition chaperone** and discuss newer regulators such as **NRF2** and **p38–TFEB** pathways.<br>- 2024 neuronal work identifies **Hspa8 as the most abundant dendritic chaperone mRNA** and shows stress-induced local translation in mouse/human neurons.<br>- 2024 cancer study shows **HSPA8 inhibitors** can potentiate necroptosis and chemotherapy response (pqac-00000005, pqac-00000013, pqac-00000017, pqac-00000007) |
| Applications/therapeutic targeting | - Pharmacologic inhibitors include **VER-155008** (ATP-competitive, NBD) and **PES/pifithrin-μ** (SBD-directed).<br>- In 2024 cancer models, HSPA8 inhibition increased sensitivity to **microtubule-targeting agents** and enhanced necroptosis-driven tumor regression.<br>- HSP70-family extracellular vesicle biology is being explored for **biomarker** and therapeutic applications, though much of that literature is not HSPA8-specific (pqac-00000007, pqac-00000018) |
| Quantitative findings | - In stressed neurons, dendrites contained roughly **~100 Hspa8 mRNAs vs ~5 Hspa1a mRNAs** on average.<br>- MG132 stress increased spines containing Hspa8 mRNA from about **~20% to ~40%**.<br>- MG132 increased translated Hspa8 mRNAs by about **20–45%** in reporter assays; differential-expression thresholds included **>1.7-fold, p<0.01** in one analysis (pqac-00000014, pqac-00000015, pqac-00000016) |


*Table: This table condenses the current evidence-based functional annotation for mouse Hspa8/HSC70 (UniProt P63017). It highlights validated structural features, core biochemical roles, major pathways, localization, and recent 2023–2024 developments useful for a final gene report.*