CD9 antigen (P21926)

Uniprot ID P21926
Protein Name CD9 antigen
Gene Name CD9
Species Homo sapiens (Human)
Signal peptide(a) N Secretome P(b) 0.302
Function Integral membrane protein associated with integrins, which regulates different processes, such as sperm-egg fusion, platelet activation and aggregation, and cell adhesion (PubMed:8478605, PubMed:14575715, PubMed:18541721). Present at the cell surface of oocytes and plays a key role in sperm-egg fusion, possibly by organizing multiprotein complexes and the morphology of the membrane required for the fusion (By similarity). In myoblasts, associates with CD81 and PTGFRN and inhibits myotube fusion during muscle regeneration (By similarity). In macrophages, associates with CD81 and beta-1 and beta-2 integrins, and prevents macrophage fusion into multinucleated giant cells specialized in ingesting complement-opsonized large particles (PubMed:12796480). Also prevents the fusion between mononuclear cell progenitors into osteoclasts in charge of bone resorption (By similarity). Acts as a receptor for PSG17 (By similarity). Involved in platelet activation and aggregation (PubMed:18541721). Regulates paranodal junction formation (By similarity). Involved in cell adhesion, cell motility and tumor metastasis (PubMed:8478605, PubMed:7511626). .
GO - Molecular function
  • integrin binding : IDA:UniProtKB
GO - Biological process
  • brain development : IEA:Ensembl
  • cell adhesion : IDA:UniProtKB
  • cellular response to low-density lipoprotein particle stimulus : ISS:UniProtKB
  • fusion of sperm to egg plasma membrane involved in single fertilization : IDA:UniProtKB
  • glial cell migration : IMP:FlyBase
  • myoblast fusion involved in skeletal muscle regeneration : ISS:UniProtKB
  • negative regulation of cell population proliferation : IEA:Ensembl
  • negative regulation of cellular component movement : IDA:UniProtKB
  • negative regulation of platelet aggregation : IDA:UniProtKB
  • oligodendrocyte development : IEA:Ensembl
  • paranodal junction assembly : ISS:UniProtKB
  • platelet activation : NAS:UniProtKB
  • platelet degranulation : TAS:Reactome
  • receptor internalization : ISS:UniProtKB
  • regulation of macrophage migration : IEA:Ensembl
  • response to water deprivation : IEA:Ensembl
  • sperm-egg recognition : ISS:UniProtKB
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(a) The Signal peptide D-score cutoff for "YES"(having signal peptide) is 0.45.
(b) Non-classically secreted proteins should obtain an NN-score(Neural Networks score) exceeding the normal threshold of 0.5, but not at the same time be predicted to contain a signal peptide.