CASPL4C2

id: B9HTK2
gene_symbol: CASPL4C2
product_type: PROTEIN
status: DRAFT
taxon:
  id: NCBITaxon:3694
  label: Populus trichocarpa
description: CASP-like protein 4C2 (PtCASPL4C2) is a small tetraspan membrane protein belonging to the
  CASP-like (CASPL) subfamily, the more divergent relatives of the bona fide Casparian strip membrane
  domain proteins (CASP1-5). Like other family members it has a central MARVEL-like four-transmembrane
  domain and is predicted to reside in the plasma membrane as a multi-pass protein. CASP-like proteins
  are not enzymes; by analogy with the characterized CASP scaffolds they are thought to organize plasma-membrane
  microdomains, but the specific biological role and tissue context of CASPL4C2 remain uncharacterized.
  Notably, by orthology within the unified CASP/CASPL nomenclature, the Arabidopsis member AtCASPL4C1
  (and its watermelon ortholog ClCASPL) is cold-inducible and broadly expressed, and acts as a negative
  regulator of growth, biomass and flowering time and a modulator of cold tolerance, apparently functioning
  in vascular tissue independently of root Casparian strip formation. The protein is predicted to form
  homodimers and heterodimers. In poplar, PtCASPL4C2 is phloem-enriched at baseline and is salt- and heat-induced
  under stress (EBI Expression Atlas E-MTAB-5540 / E-GEOD-81077).
existing_annotations:
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: CASPL4C2 is a multi-pass membrane protein of the CASP-like family; plasma membrane localization
      is the supported cellular component and the only well-grounded annotation for this otherwise uncharacterized
      protein.
    action: ACCEPT
    reason: UniProt reports cell membrane (plasma membrane) localization as a multi-pass membrane protein,
      consistent with the CASP/CASPL family and the four predicted transmembrane helices in the sequence
      record.
    supported_by:
    - reference_id: file:POPTR/CASPL4C2/CASPL4C2-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Cell membrane'
    - reference_id: file:POPTR/CASPL4C2/CASPL4C2-uniprot.txt
      supporting_text: DR   GO; GO:0005886; C:plasma membrane; IEA:UniProtKB-SubCell.
references:
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping,
    accompanied by conservative changes to GO terms applied by UniProt
  findings:
  - statement: GO_REF:0000044 supplied the plasma membrane GOA annotation reviewed in this file.
- id: file:POPTR/CASPL4C2/CASPL4C2-uniprot.txt
  title: UniProtKB reviewed entry for CASPL4C2
  findings:
  - statement: UniProt identifies CASPL4C2 as a CASP-like protein of the Casparian strip membrane proteins
      family, a multi-pass cell membrane protein.
- id: file:POPTR/CASPL4C2/CASPL4C2-goa.tsv
  title: QuickGO GOA annotations for CASPL4C2
  findings:
  - statement: GOA supplied the plasma membrane annotation reviewed in this file.
- id: PMID:24920445
  title: Functional and evolutionary analysis of the CASPARIAN STRIP MEMBRANE DOMAIN PROTEIN family.
  findings:
  - statement: Defines the CASP/CASPL family and distinguishes the divergent, largely uncharacterized
      CASP-like subfamily from the bona fide Casparian strip CASP proteins.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-verified; family-defining paper that establishes the CASP/CASPL nomenclature
      and the uncharacterized status of the CASP-like subfamily to which this protein belongs.
- id: PMID:26399665
  title: A Casparian strip domain-like gene, CASPL, negatively alters growth and cold tolerance.
  findings:
  - statement: The CASPL4C1 ortholog (Arabidopsis AtCASPL4C1; watermelon ClCASPL), in the same subfamily
      as this poplar protein, localizes to the plasma membrane, is cold-inducible and broadly expressed,
      and negatively regulates growth, biomass and flowering time while modulating cold tolerance, acting
      beyond root Casparian strip formation.
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: PubMed-verified (full text in cache). Characterizes the Arabidopsis/watermelon CASPL4C1
      ortholog, not this poplar gene directly; supplies orthology-based functional hypotheses (cold tolerance,
      growth/biomass regulation, vascular role) for this subfamily.
- id: file:projects/CASPL_FAMILY/bioinformatics/expression/RESULTS.md
  title: Poplar CASPL expression analysis (EBI Expression Atlas) - RESULTS
  findings:
  - statement: PtCASPL4C2 is phloem-enriched and salt/heat-induced, consistent with a stress-associated
      CASPL4C-clade role.
core_functions:
- description: Predicted plasma-membrane CASP-like family protein of uncharacterized specific function,
    inferred to act in organizing plasma-membrane microdomains.
  supported_by:
  - reference_id: file:POPTR/CASPL4C2/CASPL4C2-uniprot.txt
    supporting_text: 'SUBCELLULAR LOCATION: Cell membrane'
  - reference_id: file:POPTR/CASPL4C2/CASPL4C2-uniprot.txt
    supporting_text: Belongs to the Casparian strip membrane proteins (CASP)
  locations:
  - id: GO:0005886
    label: plasma membrane
proposed_new_terms: []
suggested_questions:
- question: Does PtCASPL4C2 modulate cold tolerance and negatively regulate growth/biomass in poplar,
    as shown for its Arabidopsis ortholog AtCASPL4C1?
- question: Is PtCASPL4C2 cold-inducible and expressed in vascular tissue rather than the root endodermal
    Casparian strip?
suggested_experiments:
- description: Generate loss- and gain-of-function poplar lines for PtCASPL4C2 and assay cold tolerance,
    growth rate, biomass and flowering time; profile cold-responsive and tissue-specific expression.
  experiment_type: genetic perturbation and stress phenotyping