Platelet activation tyrosine kinase

Emerging Concepts of Platelet Activation Tyrosine Kinase Phosphorylation. 247... 

AsaaanaN, Qzdd Y, SaUdi K, Yatomi Y, Handa M, Fujimura Y, Nfiura S, Kume S. Glycoprotein Ib-von Willebrand fiidor interactions activate tyrosine kinases in human platelets. Blood 1997 90 4789-98. 

A large and diverse group of proteins, including enzymes, cytoskeleton, contractile proteins, and receptors, have been shown to be modified by calpains. Thus, a number of enzymes such as tyrosine hydrolase, tryptophan hydrolase, transglutaminase, protein kinase C, and membrane Ca2+-ATPase are activated by calpain proteolysis [38]. Several receptor proteins, in particular receptors for steroid hormones, growth factors, and adrenaline, are modulated by calpains, which participate also in platelet activation, cell fusion, and mitosis [39], Although the physiological roles of calpains continue to be un-... 

Yang, L., Yatomi, Y., Hisano, N., Qi, R., Asazuma, N., Satoh, K.., Igarashi, Y., Ozaki, Y. and Kume, S., 1996, Activation of protein-tyrosine kinase Syk in human platelets stimulated with lysophosphatidic acid or sphingosine 1 -phosphate. Biochem. Biophys. 

Insulin, growth factors Monomeric Tyrosine kinase activity of receptor Insulin Insulin-like growth factor (IGF) Platelet-derived growth factor (PDGF) Epidermal growth ftictor (EGF)... 

The integrins do not have any enzyme activity in their own cytoplasmic domain, but on hgand binding, stimulation of tyrosine phosphorylation is observed on the cytoplasmic side of many cells, such as fibroblasts and platelets. The exact configuration of protein-protein interactions on the cytosolic side of the integrins is not clear and the mechanism of stimulation of protein tyrosine kinases is unknown. Some components of the focal adhesion points, such as the structural protein tensin, have SH2 and SH3 domains that may serve as specific attachment points for tyrosine kinases and other signal proteins. 

Although Gleevec was carefully designed to inhibit the specific tyrosine kinase produced by the Philadelphia chromosome, it also produces unexpected activities. Gleevec blocks c-kit (the receptor for stem cell factor) [40], and the receptor for platelet-derived growth factor [41]. These additional activities could result in a broader array of antitumor activities, in a broader spectrum of toxicities, or both [42]. 

The receptors for one of the colony-stimulating factors (M-CSF) and for platelet-derived growth factor (PDGF) are also membrane proteins with tyrosine kinase activity. Al-... 

---