Protein Tyrosine Kinase信号通路图概览
Protein tyrosine kinases play an important role in signal transduction pathways in regulating a number of cellular functions. Two classes of PTKs are present in cells: the transmembrane receptor PTKs and the nonreceptor PTKs. The RTK family includes the receptors for insulin and for many growth factors, such as EGF, FGF, PDGF, VEGF, and NGF. RTKs are transmembrane glycoproteins that are activated by the binding of their ligands, and they transduce the extracellular signal to the cytoplasm by phosphorylating tyrosine residues on the receptors themselves (autophosphorylation) and on downstream signaling proteins. RTKs activate numerous signaling pathways within cells, leading to cell proliferation, differentiation, migration, or metabolic changes. In addition, nonreceptor tyrosine kinases (NRTKs), which include Src, JAKs, and Abl, among others, are integral components of the signaling cascades triggered by RTKs and by other cell surface receptors such as GPCRs and receptors of the immune system. NRTKs are critical components in the regulation of the immune system.