FIGURE 7-17 Synopsis of the regulation of expression of the insulin gene. The primary transcription of the insulin gene is selectively stimulated by elevated cAMP and/or glucose. In addition, insulin mRNA levels are stabilized at high glucose levels, which also selectively stimulates the translation of insulin mRNA at the levels of initiation, elongation, and interaction of signal recognition particles (SRP) with a docking protein (DP) [Modified with permission from Steiner, D. F., Bell, G. I., Tager, H. S., and Rubenstein, A. H. (1995). Chemistry and biosynthesis of the islet hormones: Insulin, islet amyloid polypeptide (amylin), glucagon, somatostatin and pancreatic polypeptide. In "Endocrinology" (L. DeGroot, M. Besser, H. G. Burger, J. L. Jameson, D. L. Loriaux, J. C. Marshall, W. D. Odell, J. T. Potts, Jr., and A. H. Rubenstein, eds.), 3rd ed., Vol. 2, Chapter 76, pp. 1296-1328. W.B. Saunders, Philadelphia, PA.]
Insulin Gene Pores
Preproinsulin Synthesis Signal Peptidase Proinsulin
Energy Dependent Transfers
30-40 min t • Proinsulin& Prohormone Converting 2-4 Enzymes ^ hours
U Golgi Lyso^ome *
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