HSPH1

HSPH1 (HSP110/HSP105) is a large ATP-binding molecular chaperone that protects proteins from aggregation and, in concert with the HSP70/HSP40 system, refolds and disaggregates misfolded substrates (PMID:36825649). Direct in vitro reconstitution established its core chaperone activities and revealed an elongated conformation by SAXS (PMID:36825649), and it physically partners with the HSP40 co-chaperone DNAJB1 in the cytosol during cellular stress (PMID:41534252) and with HSPA5/BiP to maintain endoplasmic reticulum homeostasis and restrain ER stress-driven apoptosis (PMID:41925682). Beyond generic proteostasis, HSPH1 stabilizes oncogenic clients: it physically binds c-Myc and Bcl-6 in aggressive B-cell lymphoma, with its silencing collapsing both proteins and abolishing tumorigenicity (PMID:25573990), and it interacts with STAT3 to enhance STAT3 phosphorylation in inflammatory lung injury (PMID:32091104). HSPH1 expression is controlled at multiple levels — transcriptionally through direct promoter binding by Sp2 in an oxidative-stress/apoptosis axis (PMID:40972724) and translationally through the m6A reader YTHDF1, which binds HSPH1 mRNA to promote its translation (PMID:38444279).

1. 2015 Medium

   Established that HSPH1 acts as a client-stabilizing chaperone for specific oncoproteins rather than only as a general housekeeping chaperone, linking it to lymphoma maintenance.

   Evidence Reciprocal Co-IP plus shRNA silencing with in vitro and in vivo tumor growth assays in B-NHL cells and primary tumors

   PMID:25573990

   Open questions at the time

   • Direct chaperone binding versus indirect stabilization of c-Myc/Bcl-6 not structurally resolved
   • ATPase dependence of the client interaction untested
   • Single lab
2. 2020 Medium

   Connected HSPH1 to inflammatory signal transduction by showing it binds STAT3 and promotes its phosphorylation downstream of KLF2 de-repression.

   Evidence Co-IP of HSPH1–STAT3, KLF2 and IL-1R1 perturbations, and HSPH1 inhibitor treatment in a rat acute lung injury model

   PMID:32091104

   Open questions at the time

   • Mechanism by which HSPH1 enhances STAT3 phosphorylation (direct vs. scaffolding) unresolved
   • Whether interaction requires chaperone activity not addressed
3. 2023 High

   Defined the biochemical and structural basis of human HSPH1 function by directly reconstituting its anti-aggregation, refolding and disaggregation activities and resolving its elongated conformation.

   Evidence In vitro chaperone assays with purified recombinant protein, SAXS, and biophysical characterization

   PMID:36825649

   Open questions at the time

   • High-resolution structure of substrate-bound state not determined
   • Cellular substrate repertoire not defined in this study
4. 2024 Medium

   Identified a translational control layer for HSPH1, showing the m6A reader YTHDF1 binds its mRNA to boost protein output independent of transcript level.

   Evidence RIP-qPCR for YTHDF1–HSPH1 mRNA binding plus protein/RNA level measurements and omics in gastric carcinogenesis

   PMID:38444279

   Open questions at the time

   • m6A sites on HSPH1 mRNA not mapped
   • Functional consequence of elevated HSPH1 for the tumor phenotype not isolated from broader YTHDF1 effects
5. 2025 Medium

   Established transcriptional regulation of HSPH1 by Sp2 and placed the Sp2/HSPH1 axis in oxidative-stress-driven apoptosis and autophagy.

   Evidence Sp2–promoter binding assay with knockdown/overexpression and ROS/apoptosis/autophagy readouts in mouse spermatogonial stem cells

   PMID:40972724

   Open questions at the time

   • Single study and single cell model
   • Direct molecular role of HSPH1 protein downstream of Sp2 not mechanistically dissected
6. 2026 Medium

   Anchored HSPH1 within the canonical HSP40 co-chaperone partnership and ER chaperone machinery, supporting its role in stress proteostasis.

   Evidence Co-IP and immunofluorescence co-localization of HSPH1–DNAJB1 in hepatic IRI models, and Co-IP of HSPH1–HSPA5 with ER ultrastructure, ERS markers and rescue experiments in cardiomyocytes

   PMID:41534252 PMID:41925682

   Open questions at the time

   • Whether HSPH1–DNAJB1 and HSPH1–HSPA5 form defined stoichiometric complexes not established
   • ATPase/nucleotide-exchange cycle linking these interactions to substrate handling untested
   • Single lab per interaction

• The cellular substrate spectrum of HSPH1 and how its nucleotide-bound states couple to client stabilization, ER homeostasis and oncoprotein maintenance remain unresolved.
• No unbiased substrate/interactome map in the corpus
• No structure of HSPH1 bound to a defined client or co-chaperone
• Mechanistic link between chaperone cycle and oncoprotein/STAT3 effects unestablished