CASP4

id: B9HQ42
gene_symbol: CASP4
product_type: PROTEIN
status: DRAFT
taxon:
  id: NCBITaxon:3694
  label: Populus trichocarpa
description: Casparian strip membrane protein 4 (PtCASP4) is a small tetraspan plasma-membrane
  protein of the CASP (Casparian Strip membrane domain Protein) family, characterized by a
  central MARVEL-like four-transmembrane domain. CASP proteins are not enzymes; they self-assemble
  into a stable, immobile membrane scaffold at the Casparian strip membrane domain of the root
  endodermis, where they recruit lignin-polymerizing machinery to drive localized lignin deposition
  in the adjacent cell wall. The resulting Casparian strip forms an apoplastic diffusion barrier
  that controls selective uptake of water and solutes. The protein localizes to the plasma membrane
  in a restricted belt-shaped band and forms homodimers and heterodimers with other CASP family members.
existing_annotations:
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: CASP4 is a multi-pass plasma-membrane protein of the CASP family; plasma membrane
      localization is the well-supported core cellular component.
    action: ACCEPT
    reason: UniProt reports cell membrane (plasma membrane) localization as a multi-pass membrane
      protein, consistent with the CASP family and the four predicted transmembrane helices in
      the sequence record.
    supported_by:
    - reference_id: file:POPTR/CASP4/CASP4-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Cell membrane'
    - reference_id: file:POPTR/CASP4/CASP4-uniprot.txt
      supporting_text: DR   GO; GO:0005886; C:plasma membrane; IBA:GO_Central.
references:
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings:
  - statement: GO_REF:0000120 supplied the plasma membrane GOA annotation reviewed in this file.
- id: file:POPTR/CASP4/CASP4-uniprot.txt
  title: UniProtKB reviewed entry for CASP4
  findings:
  - statement: UniProt identifies CASP4 as a Casparian strip membrane protein, a multi-pass cell
      membrane protein required for establishment of the Casparian strip membrane domain.
- id: file:POPTR/CASP4/CASP4-goa.tsv
  title: QuickGO GOA annotations for CASP4
  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 nomenclature and the role of CASP proteins as plasma-membrane
      scaffolds for Casparian strip formation.
core_functions:
- description: Plasma-membrane scaffold protein of the CASP family that organizes the Casparian
    strip membrane domain to direct localized cell-wall (lignin) deposition in the root endodermis.
  supported_by:
  - reference_id: file:POPTR/CASP4/CASP4-uniprot.txt
    supporting_text: Required for establishment of the Casparian strip
  - reference_id: file:POPTR/CASP4/CASP4-uniprot.txt
    supporting_text: 'SUBCELLULAR LOCATION: Cell membrane'
  locations:
  - id: GO:0005886
    label: plasma membrane
proposed_new_terms: []
suggested_questions:
- question: Is PtCASP4 expressed specifically in the root endodermis and localized to the Casparian
    strip membrane domain in poplar, as predicted from its Arabidopsis orthologs?
suggested_experiments:
- description: Express a fluorescently tagged PtCASP4 in poplar roots and image its subcellular
    localization to test for a belt-shaped Casparian strip membrane domain band in the endodermis.
  experiment_type: localization imaging