Insulin signal transmission

M. F. White, J. N. Livingston, J. M. Backer, V. Lauris, T. J. Dull, A. Ullrich, and C. R Kahn. Mutation of the insulin receptor at tyrosine 960 inhibits signal transmission but does not affect its tyrosine kinase activity. Cell, 54 (5), 641-649, 1988... 

The function of Tyr-1316 and -1322 at the C-terminus, which contains 20-30% of the phosphate (Tornqvist et al., 1988 White et al., 1988b), is not known. They are obviously not important for kinase activity, but may be related to growth signals (Debant et al., 1988). Moreover studies with proteolytically truncated receptor at the C-terminus suggest a role for this region in the specificity for signal transmission of the insulin receptor. Related receptors such as the IGF-I receptor and the insulin receptor-related receptor lack some of these tyrosine-phosphorylation sites at the C-terminus. 

After insulin binding, protein phosphorylation and dephosphorylation appear to play a pivotal role in further signal transmission from the insulin receptor to the effector systems (Goldstein, 1992). Since at the post-kinase level tyrosine phosphorylation of substrate proteins is involved in insulin signalling, an important role for tyrosine phosphatases in the regulation of post-kinase signalling mechanisms has to be assumed (Goldstein, 1992). 

FIGURE 12-8 Activation of glycogen synthase by insulin. Transmission of the signal is... 

The alkaline earth metals (group 2A of the periodic table) include Mg and Ca, which play both structural and physiological roles. Aside from its structural importance in bones and teeth, calcium is critical in processes ranging from vascular tone, nerve impulse transmission, muscle contraction, blood clot formation, the secretion of hormones such as insulin, and cell signaling. Calcium levels in cells, blood, and extracellular fluid are very tightly controlled. If calcium intake is insufficient, calcium is liberated from bones in order to support these physiological functions. 

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