Catalytic domain of the Serine/Threonine Kinase, Classical Protein Kinase C beta
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. The PKC beta isoforms (I and II), generated by alternative splicing of a single gene, are preferentially activated by hyperglycemia-induced DAG (1,2-diacylglycerol) in retinal tissues. This is implicated in diabetic microangiopathy such as ischemia, neovascularization, and abnormal vasodilator function. PKC-beta also plays an important role in VEGF signaling. In addition, glucose regulates proliferation in retinal endothelial cells via PKC-betaI. PKC-beta is also being explored as a therapeutic target in cancer. It contributes to tumor formation and is involved in the tumor host mechanisms of inflammation and angiogenesis. PKCs are classified into three groups (classical, atypical, and novel) depending on their mode of activation and the structural characteristics of their regulatory domain. PKCs undergo three phosphorylations in order to take mature forms. In addition, cPKCs depend on calcium, DAG, and in most cases, phosphatidylserine (PS) for activation. The cPKC-beta subfamily is part of a larger superfamily that includes the catalytic domains of other protein STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
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