id: Q9UF47
gene_symbol: DNAJC5B
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: DNAJC5B (cysteine-string protein isoform beta, CSP-beta) is a testis-specific
  paralog of the synaptic co-chaperone CSPalpha/DNAJC5. Like other cysteine string
  proteins it has an N-terminal J domain that engages the constitutive HSP70 chaperone
  HSC70/HSPA8 and a downstream cysteine-string region that can be palmitoylated. CSP-beta
  interacts with the HSC70-SGTA chaperone complex and is membrane-anchored, associating
  with the trans-Golgi network; unlike CSPalpha its membrane association does not require
  palmitoylation. Its physiological role is presumed to be HSP70 co-chaperone activity
  in a secretory/membrane-trafficking context of the testis, but it is otherwise poorly
  characterized.
existing_annotations:
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  qualifier: located_in
  review:
    summary: Electronic cytoplasm annotation. CSP-beta is a membrane-anchored co-chaperone
      with a cytoplasmic-facing pool.
    action: KEEP_AS_NON_CORE
    reason: Generic cytoplasm localization; consistent with a J-domain co-chaperone
      but less informative than its membrane/TGN association.
    supported_by:
    - reference_id: file:human/DNAJC5B/DNAJC5B-uniprot.txt
      supporting_text: Interacts with the chaperone complex consisting of HSC70
- term:
    id: GO:0016020
    label: membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Membrane localization from UniProt subcellular-location mapping, experimentally
      supported by detection as a lipid-anchored, TGN-associated protein.
    action: ACCEPT
    reason: CSP-beta is experimentally documented as a membrane (lipid-anchor) protein
      that may associate with the trans-Golgi network; membrane is its core compartment.
    supported_by:
    - reference_id: file:human/DNAJC5B/DNAJC5B-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Membrane'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:25416956
  qualifier: enables
  review:
    summary: Proteome-scale yeast two-hybrid map capturing a CSP-beta-TFCP2 interaction.
      The bare protein binding term is uninformative and the partner (the transcription
      factor TFCP2/CP2) does not define a chaperone function.
    action: KEEP_AS_NON_CORE
    reason: Records a single high-throughput interaction; bare protein binding is
      uninformative and is not elevated to core.
    supported_by:
    - reference_id: file:human/DNAJC5B/DNAJC5B-uniprot.txt
      supporting_text: 'Q9UF47; Q12800: TFCP2; NbExp=3'
references:
- id: GO_REF:0000044
  title: Gene Ontology annotation through association of InterPro records with GO
    terms
  findings: []
- id: GO_REF:0000117
  title: Electronic Gene Ontology annotations created by ARBA machine learning models
  findings: []
- id: PMID:25416956
  title: A proteome-scale map of the human interactome network.
  findings: []
- id: PMID:17034881
  title: Cysteine-string protein isoform beta (Cspbeta) is targeted to the trans-Golgi
    network as a non-palmitoylated CSP in clonal beta-cells.
  reference_review:
    relevance: HIGH
    correctness: UNVERIFIED
    review_notes: "Primary functional reference for CSP-beta/DNAJC5B: reports its
      membrane targeting to the trans-Golgi network and association with the HSC70/
      SGTA chaperone complex, the basis for the co-chaperone and membrane-localization
      annotations. Not cached in publications/, so the identifier/content could not be
      checked against a cached/PubMed anchor; title is consistent with the claim but
      left UNVERIFIED."
  findings:
  - statement: CSP-beta interacts with the HSC70 and SGTA chaperone complex and is
      a membrane-anchored protein targeted to the trans-Golgi network; its membrane
      association does not require palmitoylation.
    reference_section_type: RESULTS
- id: file:human/DNAJC5B/DNAJC5B-uniprot.txt
  title: UniProt entry Q9UF47 (DNJ5B_HUMAN), cysteine-string protein isoform beta
  findings:
  - statement: Testis-specific CSP paralog; J domain (aa 19-84); interacts with the
      HSC70/SGTA chaperone complex; membrane lipid-anchor associated with the trans-Golgi
      network; palmitoylated but palmitoylation is not required for membrane association.
    reference_section_type: OTHER
core_functions:
- description: HSP70/HSC70 co-chaperone defined by an N-terminal J domain, experimentally
    shown to interact with the HSC70-SGTA chaperone complex; acts in a testis-specific,
    membrane/trans-Golgi-network context.
  molecular_function:
    id: GO:0030544
    label: Hsp70 protein binding
  locations:
  - id: GO:0016020
    label: membrane
  supported_by:
  - reference_id: file:human/DNAJC5B/DNAJC5B-uniprot.txt
    supporting_text: Interacts with the chaperone complex consisting of HSC70
proposed_new_terms: []
suggested_questions:
- question: What is the testis-specific physiological function of CSP-beta, and does
    it chaperone a secretory or membrane-trafficking client analogous to CSPalpha's
    SNAP-25?
- question: Does CSP-beta stimulate HSC70 ATPase activity via its J domain, and how
    does its palmitoylation-independent membrane targeting differ mechanistically
    from CSPalpha?
suggested_experiments:
- description: Reconstituted HSC70 ATPase assays with purified CSP-beta (wild-type
    and J-domain HPD mutant) to confirm co-chaperone activity.
- description: Affinity purification-mass spectrometry of tagged CSP-beta from a testis-derived
    or beta-cell line to identify its client/interaction network and any secretory-pathway
    partners.