CD49b ITGA2 (integrin α 2 subunit of VLA-2 receptor), VLA-2α chain, platelet GPIa
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
Type 1 glycoprotein
B Lymphocyte
Monocyte
NK Cell
Platelet
Fibroblast
Lymphocyte
T Cell
Endothelial Cell
Megakaryocyte
Epithelial Cell
160 / 160
165 / 165

Expression
CD49b is expressed on monocytes, platelets, megakaryocytes, activated T cells, B lymphocytes, epithelial cells,endothelial cells, fibroblasts and NK cells.  The level of expression on T cells is elevated upon prolonged culture.  Like CD49a/CD29, CD49b/CD29 is also found on lymphocytes in the synovial joints of rheumatoid patients.  In contrast to CD49a/CD29, CD49b/CD29 is further upregulated on stimulation with phytohemagglutinin.

Structure
MOLECULAR FAMILY NAME: Belongs to the integrin a chain family.

CD49b is a single-pass type-1 1152 aa glycoprotein.  It contains a large extracellular domain which contains an I domain which combines with β1 integrin to form a collagen-binding intrgrin and has 10 potential N-glycosylation sites,a transmembrane domain and a 27 aa cytoplasmic domain.  All integrin α chains have a conserved sequence found in the cytoplasmic domain immediately following the transmembrane domain (FYWS)-(RK)-x-G-F-F-x-R, which may be the motif involved in heterodimer formation.  CD47b is an a2 integrin subunit which forms a non-covalently associated heterodimer with the CD29 molecule to form α2/b1 integrin subunit.  The N-terminal sequence of CD49b has been determined.  A polymorphism at residue 505 gives rise to the platelet alloantigenic Br a, Lys, and Br b, Glu, variants.

MOLECULAR MASS
Cell Type Unreduced Reduced
160 kDa 165 kDa

POST-TRANSCRIPTIONAL MODIFICATION: No information.

POST-TRANSLATIONAL MODIFICATION: No information.


Ligands
LIGANDS AND MOLECULES ASSOCIATED WITH CD49b

CD49b/CD29 binds type I collagen, VLA-3, E-cadherin and is a receptor for echovirus 1. Binding to both ligands can be inhibited by peptides containing the DGEA sequence.  The I-domain of CD49b is involved in collagen binding.

Function
CD49b mediates cell adhesion to collagen and laminin.  CD49b is reported to be important in the maintenance of endothelial monlayer integrity along with CD49e.  CD49b acts as a collagen and echovirus 1 receptor, and participates in adhesion and in cell-surface mediating signaling.  In vitro studies have shown enhancement of effector T-cell proliferation and cytokine production when bound to collagen via VLA-2.  CD49b/CD29 mediates the Mg2+-dependent adhesion of platelets to collagen.  It is also a collagen receptor on leukocytes and fibroblasts.  CD49b/CD29 can act as a echovirus 1 receptor on certain cell lines but not in platelets or fibroblasts.  CD49b/CD29 integrin is a receptor for echovirus.

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD49b IN INTACT ANIMAL

CD49b has a role in blood clotting and angiogenesis.  The upregulation of CD49b/CD29 may be used by tumor cells to remodel the collagen matrix during tumor growth, invasion and metastasis.   CD49b modulates effector inflammatory responses in vivo and may be utilized by fibroblasts for the reorganization of the collagen matrix during wound healing.
              

Comments
MOLECULAR INTERACTIONS-
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD49b: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD49b: No information.


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
CattleL25886
HumanEntrezgene 3672P17301
Antibodies
12F1-H6   View Reactivity
16B4   View Reactivity
AK7   View Reactivity

Revised June 25, 2008


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