The human megakaryocytic cell line UT-7/TPO expresses functional platelet agonist signals mediated through GPVI and thromboxane receptor.
We have demonstrated that a unique megakaryocytic cell line UT-7/TPO could respond to one of the primary platelet signals through GP (glycoprotein) VI and a secondary signal of the AA (arachidonic acid) cascade. Unlike other megakaryocytic cell lines, UT-7/TPO was found to express GPVI and its associate signal molecule of FcRgamma (Fc receptor gamma chain). When UT-7/TPO was stimulated with the GPVI agonist convulxin, the [Ca2+]i (intracellular Ca2+) was elevated in a convulxin concentration-dependent manner, and [Ca2+]i elevation was blocked by pretreatment with the Src family kinase inhibitor PP2 and the phospholipase inhibitor U73122. These results strongly indicate that endogenously expressed GPVI signal molecules are functional in UT-7/TPO. Concerning the AA cascade, the expression of COX (cyclooxygenase)-1 and TX (thromboxane) synthase was observed, and this cell line was able to produce TX by exogenous AA, followed by [Ca2+]i elevation mediated through the TX receptor. It is worth noting that convulxin stimulation did not cause TX generation, even through the GPVI pathway and the AA cascade are functional in this cell line. As there are many reports that convulxin-stimulated platelets failed to produce TX, it is suggested that UT-7/TPO has the same property as the platelets in regards to convulxin stimulation. Thus, UT-7/TPO is useful for the observation of both the GPVI pathway and AA cascade without requiring either the induction of differentiation or GPVI transfection. Furthermore, this cell line provides a new tool for research on platelet activation signals.
Kawaguchi
Tatsuya
T
Exploratory Research Laboratories II, DaiichiSankyo Co., Ltd, 11613, Kitakasai, Edogawaku, Tokyo 1348630, Japan. kawaguchi.tatsuya.ns@daiichisankyo.co.jp
Hashimoto
Ryuji
R
Yokota
Hiroshi
H
D016718:Arachidonic Acid / Q000494:pharmacology; D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003435:Crotalid Venoms / Q000494:pharmacology; D051545:Cyclooxygenase 1 / Q000378:metabolism; D006801:Humans; D037181:Lectins, C-Type; D008533:Megakaryocytes / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D019000:Phosphotyrosine / Q000378:metabolism; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D017452:Receptors, IgG / Q000378:metabolism; D017482:Receptors, Thromboxane / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013929:Thromboxane B2 / Q000096:biosynthesis; D013930:Thromboxane-A Synthase / Q000378:metabolism
D003435:Crotalid Venoms; D037181:Lectins, C-Type; D010980:Platelet Membrane Glycoproteins; D017452:Receptors, IgG; D017482:Receptors, Thromboxane; C098341:platelet membrane glycoprotein VI; D019000:Phosphotyrosine; D016718:Arachidonic Acid; C028890:convulxin; D013929:Thromboxane B2; D051545:Cyclooxygenase 1; C496511:PTGS1 protein, human; D013930:Thromboxane-A Synthase; D002118:Calcium