Expression of the collagen receptor glycoprotein VI during megakaryocyte differentiation

This study examined the expression of the platelet collagen receptor glycop rotein VI (GPVI) in megakaryocyte cell lines and primary megakaryocytes by reverse transcriptase-polymerase chain reaction and by flow cytometry and l igand blotting using the snake venom toxin convulxin. Expression of GPVI is increased in the megakaryoblastic cell lines HEL and CMK on differentiatio n with the phorbol ester phorbol 12-myristate Il-acetate (PMA), along with the Fe receptor gamma -chain (FcR gamma -chain). The increase in GPVI expre ssion is associated with marked potentiation of tyrosine phosphorylation an d Ca++ elevation in response to convulxin. Syk, linker for activated T cell s, and phospholipase C gamma2 (PLC gamma2) are among the proteins tyrosine phosphorylated on convulxin stimulation in PMA-differentiated HEL cells. St udies on primary murine megakaryocytes grown in vitro confirmed that GPVI i s up-regulated in parallel with functional activation, assessed by measurem ent of [Ca++](i), during differentiation. The results demonstrate that expr ession of GPVI is upregulated along with the FcR gamma -chain during differ entiation of megakaryocytes, (C) 2000 by The American Society of Hematology .