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 13-acetate (PMA), along with
the pc receptor gamma-chain (FcR gamma-chain). The increase in GPVI express
ion is associated with marked potentiation of tyrosine phosphorylation and
Ca++ elevation in response to convulxin, Syk, linker for activated T cells,
and phospholipase C gamma 2 (PLC gamma 2) 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 differe
ntiation of megakaryocytes, (Blood, 2000;96:2740-2745) (C) 2000 by The Amer
ican Society of Hematology.