id: Q96MM6 gene_symbol: HSPA12B product_type: PROTEIN status: COMPLETE taxon: id: NCBITaxon:9606 label: Homo sapiens description: >- HSPA12B is an endothelial-enriched, non-canonical HSP70-family protein with an atypical HSP70-like ATPase domain. The strongest experimental literature supports roles in endothelial cell migration, angiogenic sprouting, and maintenance of endothelial integrity during vascular stress. More recent work links HSPA12B to endothelial homeostasis during aging via XBP1-dependent ER-associated degradation of STING. Direct biochemical evidence for canonical HSP70 chaperone activity, unfolded-protein binding, or a core proteostasis function is lacking. existing_annotations: - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:25416956 review: summary: >- This annotation comes from a proteome-scale interactome map that reported HSPA12B binary interactions with proteins such as KRT31, KRT40, and NOTCH2NLA. The underlying study does not define a specific biochemical activity for HSPA12B. action: MARK_AS_OVER_ANNOTATED reason: >- GO:0005515 is too generic to be curatorially useful here. Large-scale interaction mapping does not establish a specific molecular function and does not support importing a canonical HSP70/proteostasis activity for HSPA12B. - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:32296183 review: summary: >- This annotation derives from the HuRI binary interactome study. It includes an HSPA12B-HSPA12A interaction along with several other high-throughput binary interaction calls. action: MARK_AS_OVER_ANNOTATED reason: >- GO:0005515 is uninformative, and this study does not resolve a specific mechanistic interaction relevant to HSPA12B's validated endothelial biology. Recurrent HSPA12A co-detection is not enough to infer a defined HSP70-family chaperone function. - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:33961781 review: summary: >- Cell-specific interactome remodeling again detected an HSPA12B-HSPA12A binary interaction. action: MARK_AS_OVER_ANNOTATED reason: >- This remains a generic high-throughput interaction claim rather than a specific molecular function. It does not justify a retained protein-binding annotation and does not strengthen the case for direct proteostasis/chaperone activity. - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:40205054 review: summary: >- A recent multimodal cell-map study again recovered HSPA12B-HSPA12A as a binary interaction. action: MARK_AS_OVER_ANNOTATED reason: >- Even with recurrence across interaction atlases, GO:0005515 remains too vague to preserve. These data still do not identify a specific biochemical activity or establish HSPA12B as a canonical HSP70 chaperone. - term: id: GO:0043542 label: endothelial cell migration evidence_type: IMP original_reference_id: PMID:16968741 review: summary: >- Knockdown and overexpression experiments in HUVECs showed that HSPA12B is required for endothelial wound healing and migration. This is a specific, experimentally supported endothelial process and is more defensible than any PN-driven chaperone assignment. action: NEW reason: >- Direct perturbation evidence supports HSPA12B involvement in endothelial cell migration. supported_by: - reference_id: PMID:16968741 supporting_text: >- Knockdown of HspA12B by small interfering RNAs (siRNAs) in human umbilical vein endothelial cells blocked wound healing, migration and tube formation, whereas overexpression of HspA12B enhanced migration and accelerated wound healing - term: id: GO:0001525 label: angiogenesis evidence_type: IMP original_reference_id: PMID:16968741 review: summary: >- Zebrafish knockdown produced sprouting-vessel defects and HUVEC perturbation impaired tube formation, supporting a role in angiogenic endothelial behavior. action: NEW reason: >- Developmental and endothelial functional assays support HSPA12B involvement in angiogenesis. supported_by: - reference_id: PMID:16968741 supporting_text: >- Morpholino-mediated knockdown of GA2692 in embryos resulted in multiple defects in vasculature, particularly, at sites undergoing active capillary sprouting: the intersegmental vessels, sub-intestinal vessels and the capillary sprouts of the pectoral fin vessel. - term: id: GO:0003713 label: transcription coactivator activity evidence_type: IDA original_reference_id: PMID:32790647 review: summary: >- Fan et al. 2020 showed that hypoxia-induced HSPA12B interacts with YAP and participates in a YAP/TEAD4 angiogenic promoter program. This gives HSPA12B a more specific molecular-function annotation than generic protein binding or assumed canonical HSP70 chaperone activity, while the Falcon synthesis appropriately notes that part of the mechanism also involves YAP stabilization. action: NEW reason: >- HSPA12B has direct pathway-level evidence for coactivator function in the endothelial YAP/TEAD4 angiogenic program. supported_by: - reference_id: PMID:32790647 supporting_text: >- ChIP assay showed that HSPA12B is a target gene of YAP/transcriptional enhanced associated domain 4 (TEAD4) and a coactivator in YAP-associated angiogenesis. - reference_id: file:human/HSPA12B/HSPA12B-deep-research-falcon.md supporting_text: >- HSPA12B also functions as a **coactivator** at YAP/TEAD4-driven promoters (e.g., CTGF). references: - id: file:human/HSPA12B/HSPA12B-deep-research-falcon.md title: Falcon deep research report for HSPA12B findings: - statement: >- Falcon supports HSPA12B as an endothelial stress-response effector involved in vascular remodeling, angiogenesis, and inflammatory endothelial-immune crosstalk, while cautioning that canonical HSP70 chaperone activity remains unproven. supporting_text: >- HSPA12B functions as an **endothelial stress-response effector** that (i) enables **adaptive vascular remodeling/angiogenesis** in ischemic injury and (ii) constrains **endothelial-driven inflammation** through regulation of adhesion molecules and exosome-mediated immune modulation. - id: PMID:25416956 title: A proteome-scale map of the human interactome network. findings: [] - id: PMID:32296183 title: A reference map of the human binary protein interactome. findings: [] - id: PMID:33961781 title: Dual proteome-scale networks reveal cell-specific remodeling of the human interactome. findings: [] - id: PMID:40205054 title: Multimodal cell maps as a foundation for structural and functional genomics. findings: [] - id: PMID:12552099 title: Two Hsp70 family members expressed in atherosclerotic lesions. findings: - statement: >- HSPA12B is a distant HSP70-family member with atypical ATPase-domain homology, and the paper explicitly stops short of assigning canonical mammalian HSP70 function. supporting_text: >- Both genes appear to contain an atypical Hsp70 ATPase domain. The BLAST search also revealed that both genes were more similar to primitive eukaryote and prokaryote than mammalian Hsp70s, making these two genes distant members of the mammalian Hsp70 family. - id: PMID:16968741 title: A novel endothelial-specific heat shock protein HspA12B is required in both zebrafish development and endothelial functions in vitro. findings: - statement: >- HSPA12B is endothelial enriched and required for endothelial migration, tube formation, and angiogenic sprouting. supporting_text: >- Knockdown of HspA12B by small interfering RNAs (siRNAs) in human umbilical vein endothelial cells blocked wound healing, migration and tube formation, whereas overexpression of HspA12B enhanced migration and accelerated wound healing - id: PMID:32790647 title: Endothelial cell HSPA12B and yes-associated protein cooperatively regulate angiogenesis following myocardial infarction. findings: - statement: >- HSPA12B interacts with YAP and functions as a YAP/TEAD4-associated coactivator in endothelial angiogenesis after hypoxic stress and myocardial infarction. supporting_text: >- ChIP assay showed that HSPA12B is a target gene of YAP/transcriptional enhanced associated domain 4 (TEAD4) and a coactivator in YAP-associated angiogenesis. - id: PMID:27644317 title: HSPA12B Attenuated Acute Myocardial Ischemia/reperfusion Injury via Maintaining Endothelial Integrity in a PI3K/Akt/mTOR-dependent Mechanism. findings: - statement: >- In myocardial ischemia/reperfusion models, endothelial HSPA12B preserved endothelial integrity and limited injury, supporting a contextual vascular-protective role rather than a direct chaperone assignment. supporting_text: >- This cardioprotective action of HSPA12B was mediated, at least in part, by improving endothelial integrity in a PI3K/Akt/mTOR-dependent mechanism. - id: PMID:32411123 title: Endothelial HSPA12B Exerts Protection Against Sepsis-Induced Severe Cardiomyopathy via Suppression of Adhesion Molecule Expression by miR-126. findings: - statement: >- Endothelial HSPA12B suppresses inflammatory adhesion-molecule biology in septic cardiomyopathy through a miR-126-associated mechanism. supporting_text: >- The data suggest that HSPA12B protects against sepsis-induced severe cardiomyopathy via regulating miR-126 expression which targets adhesion molecules, thus decreasing the accumulation of immune cells in the myocardium. - id: PMID:41063400 title: HSPA12B Protects Against Age-Related Endothelial Cell Senescence by Regulating STING Degradation. findings: - statement: >- Recent evidence places HSPA12B in an endothelial XBP1-SEL1L-HRD1-STING axis that preserves endothelial homeostasis during aging. supporting_text: >- Collectively, these findings reveal a previously unrecognized role for HSPA12B in preserving endothelial homeostasis during aging by regulating XBP1-mediated ER-associated degradation of STING - id: file:human/HSPA12B/HSPA12B-hypotheses/hsp70-folding-machinery-check/openscientist.md title: 'OpenScientist hypothesis run: HSPA12B HSP70 folding-machinery check' findings: - statement: Confirms HSPA12B is a divergent non-canonical HSP70 for which GO:0140662 (ATP-dependent protein folding chaperone) should not be assigned; it retains only the actin-like ATPase fold and is neofunctionalized in endothelial angiogenesis signaling. Corroborates the PN workbook InterPro domain deficit (only the root ATPase fold is shared with canonical HSPA8). supporting_text: has lost the molecular machinery required for ATP-dependent protein folding - id: file:human/HSPA12B/HSPA12B-notes.md title: Manual notes on HSPA12B PN context and literature review findings: [] aliases: - C20orf60 core_functions: - description: >- HSPA12B acts in endothelial stress responses as a YAP/TEAD4-associated coactivator and signaling effector that promotes endothelial migration, tube formation, and angiogenic vascular remodeling after ischemic injury. This endothelial function is better supported than assigning a canonical HSP70 ATP-dependent chaperone activity, which remains biochemically unresolved for HSPA12B. molecular_function: id: GO:0003713 label: transcription coactivator activity directly_involved_in: - id: GO:0043542 label: endothelial cell migration - id: GO:0001525 label: angiogenesis supported_by: - reference_id: PMID:16968741 supporting_text: >- Knockdown of HspA12B by small interfering RNAs (siRNAs) in human umbilical vein endothelial cells blocked wound healing, migration and tube formation, whereas overexpression of HspA12B enhanced migration and accelerated wound healing - reference_id: file:human/HSPA12B/HSPA12B-deep-research-falcon.md supporting_text: >- HSPA12B functions as an **endothelial stress-response effector** that (i) enables **adaptive vascular remodeling/angiogenesis** in ischemic injury and (ii) constrains **endothelial-driven inflammation** through regulation of adhesion molecules and exosome-mediated immune modulation. suggested_questions: - question: >- Does HSPA12B have bona fide ATP-dependent chaperone activity or unfolded-client binding, or is the HSP70 classification only structural and evolutionary? - question: >- Which direct biochemical partners mediate HSPA12B's endothelial phenotypes, including the reported XBP1/STING axis? suggested_experiments: - description: >- Purify HSPA12B and test ATP hydrolysis, unfolded-client binding, aggregation suppression, and refolding activity against canonical HSP70 controls. experiment_type: biochemistry hypothesis: >- If HSPA12B is a true HSP70-like chaperone, it should show direct ATP-dependent client handling or measurable holdase/foldase activity. - description: >- Perform endothelial CRISPR loss-of-function and rescue experiments with separation-of-function HSPA12B mutants to distinguish migration/angiogenesis phenotypes from stress-protective XBP1-ERAD-STING effects. experiment_type: cell biology hypothesis: >- Distinct regions of HSPA12B may underlie endothelial motility versus stress-response/homeostasis phenotypes.