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Details on Person UniProt:P21926 CD9

Class:Id	ReferenceGeneProduct:51718
_chainChangeLog	initiator methionine:1 added on Fri February 6 2015;chain:2-228 added on Fri February 6 2015;initiator methionine:1 for 51718 removed on Fri Nov 03 2023;initiator methionine: for 51718 added on Fri Nov 03 2023;initiator methionine: for 51718 removed on Fri Aug 15 2025;initiator methionine:1 for 51718 added on Fri Aug 15 2025
_displayName	UniProt:P21926 CD9
_timestamp	2025-08-15 20:58:37
chain	initiator methionine:1 chain:2-228
checksum	F68333E0C20611D8
comment	FUNCTION Integral membrane protein associated with integrins, which regulates different processes, such as sperm-egg fusion, platelet activation and aggregation, and cell adhesion (PubMed:14575715, PubMed:18541721, PubMed:8478605). 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:7511626, PubMed:8478605).SUBUNIT Forms both disulfide-linked homodimers and higher homooligomers as well as heterooligomers with other members of the tetraspanin family (PubMed:14556650). Interacts (via the second extracellular domain) with integrin ITGAV:ITGB3 (PubMed:19640571, PubMed:27993971). Interacts with integrin ITGA6:ITGB1; interaction takes place in oocytes and is involved in sperm-egg fusion (By similarity). Part of integrin-tetraspanin complexes composed of CD81, beta-1 and beta-2 integrins in the membrane of monocyte/macrophages (PubMed:12796480). Interacts with CD63; identified in a complex with CD63 and ITGB3 (PubMed:19640571). Associates with CR2/CD21 and with PTGFRN/CD9P1 (PubMed:11278880). Part of a complex composed of CD9, CD81, PTGFRN and IGSF8 (By similarity). Interacts directly with IGSF8 (PubMed:11504738). Interacts with PDPN; this interaction is homophilic and attenuates platelet aggregation and pulmonary metastasis induced by PDPN (PubMed:18541721). Interacts (on T cell side) with CD81 at immunological synapses between antigen-presenting cells and T cells (PubMed:23858057).INTERACTION Present at the cell surface of oocytes. Accumulates in the adhesion area between the sperm and egg following interaction between IZUMO1 and its receptor IZUMO1R/JUNO.TISSUE SPECIFICITY Detected in platelets (at protein level) (PubMed:19640571). Expressed by a variety of hematopoietic and epithelial cells (PubMed:19640571).PTM Palmitoylated at a low, basal level in unstimulated platelets. The level of palmitoylation increases when platelets are activated by thrombin (in vitro). The protein exists in three forms with molecular masses between 22 and 27 kDa, and is known to carry covalently linked fatty acids (PubMed:11959120). Palmitoylation by ZDHHC2 regulates CD9 expression, association with other tetraspanin family proteins and function in cell adhesion (PubMed:18508921).SIMILARITY Belongs to the tetraspanin (TM4SF) family.
description	recommendedName: fullName evidence="19"CD9 antigen alternativeName: 5H9 antigen alternativeName: fullName evidence="22"Cell growth-inhibiting gene 2 protein alternativeName: Leukocyte antigen MIC3 alternativeName: fullName evidence="21"Motility-related protein shortName evidence="21"MRP-1 alternativeName: Tetraspanin-29 shortName: Tspan-29 alternativeName: fullName evidence="20"p24 cdAntigenName evidence="19"CD9/cdAntigenName
geneName	CD9 MIC3 TSPAN29 GIG2
identifier	P21926
isSequenceChanged	FALSE
keyword	3D-structure Cell adhesion Cell membrane Direct protein sequencing Disulfide bond Fertilization Glycoprotein Lipoprotein Membrane Palmitate Proteomics identification Reference proteome Secreted Transmembrane Transmembrane helix
modified	[InstanceEdit:9836292] Weiser, Joel, 2023-05-25 [InstanceEdit:9852000] Weiser, Joel, 2023-11-03 [InstanceEdit:9917590] Weiser, Joel, 2024-08-09 [InstanceEdit:9926675] Weiser, Joel, 2024-11-03 [InstanceEdit:9963647] Weiser, Joel, 2025-08-15
name	CD9
referenceDatabase	[ReferenceDatabase:2] UniProt
referenceGene	[ReferenceDNASequence:8961060] ENSEMBL:ENSG00000010278 CD9 [Homo sapiens]
secondaryIdentifier	CD9_HUMAN D3DUQ9 Q5J7W6 Q96ES4
sequenceLength	228
species	[Species:48887] Homo sapiens
(referenceEntity)	[EntityWithAccessionedSequence:51717] CD9 [plasma membrane] [Homo sapiens] [EntityWithAccessionedSequence:114585] CD9 [platelet alpha granule membrane] [Homo sapiens] [EntityWithAccessionedSequence:5334774] CD9 [endocytic vesicle membrane] [Homo sapiens] [EntityWithAccessionedSequence:5334779] CD9 [clathrin-coated endocytic vesicle membrane] [Homo sapiens] [EntityWithAccessionedSequence:8961196] CD9 [extracellular region] [Homo sapiens]
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No pathways have been reviewed or authored by UniProt:P21926 CD9 (51718)