CD9/Motility-Related Protein-1

CD9 antigen is a 24 to 27 kD glycoprotein expressed on the surface of developing B lymphocytes, platelets, monocytes, eosinophils, basophils, stimulated T lymphocytes and by neurons and glial cells in the peripheral nervous system. It belongs to a family of membrane proteins termed tetraspanins that transverse the membrane four times. In pre-B cells and platelets, CD9 antigen regulates cell activation aggregation possibly through an association with the integrin CD41/ CD61 (GPIIb/GPIIIa). It also regulates cell motility in a variety of cell lines, and appears to be an important regulator of Schwann cell behaviour in peripheral nerve.