The proinsulin C-peptide—a multirole model

The C-peptide links the insulin A and B chains in proinsulin, providing thereby a means to promote their efficient folding and assembly in the endoplasmic reticulum during insulin biosynthesis. It then facilitates the intracellular transport, sorting, and proteolytic processing of proinsulin into biologically active insulin in the maturing secretory granules of the β cells. These manifold functions impose significant constraints on the C-peptide structure that are conserved in evolution. After cleavage of proinsulin, the intact C-peptide is stored with insulin in the soluble phase of the secretory granules and is subsequently released in equimolar amounts with insulin, providing a useful independent indicator of insulin secretion. This brief review highlights many aspects of its roles in biosynthesis, as a prelude to consideration of its possible additional role(s) as a physiologically active peptide after its release with insulin into the circulation in vivo

Influence of CO(2) pneumoperitoneum on intracellular pH and signal transduction in cancer cells

Object: The authors studied the influence of CO(2) pneumoperitoneum on intracellular pH and signal transduction arising from cancer cell multiplication in laparoscopic tumor operation. Method: They set up a simulation of pneumoperitoneum under different CO(2) pressure, and then measured the variation of intracellular pH (pHi) at different time and the activity of protein kinase C (PKC) and protein phosphatase 2a (PP2a) at the end of the pneumoperitoneum. After 1 week, the concentration of cancer cells in the culture medium was calculated. Result: When the pressure of CO(2) pneumoperitoneum was 0, 10, 20, 30 mmHg respectively, the average pHi was 7.273, 7.075, 6.783, 6.693 at the end of the pneumoperitoneum; PKC activity was 159.4, 168.5, 178.0, 181.6 nmol/(g·min) and PP2a was 4158.3, 4066.9, 3984.0, 3878.5 nmol/(g·min) respectively. After 1 week, the cancer cells concentration was 2.15×10(5), 2.03×10(5), 2.20×10(5), 2.18×10(5) L(−1). Conclusion: CO(2) pneumoperitoneum could promote acidosis in cancer cells, inducing the activation of protein kinase C and deactivation of protein phosphatase 2a, but it could not accelerate the mitosis rate of the cancer cells

Embryonic Cell Lines with Endothelial Potential: An in Vitro System for Studying Endothelial Differentiation

10.1161/01.ATV.0000120375.51196.73Arteriosclerosis, Thrombosis, and Vascular Biology244691-696ATVB

Multifaceted biological insights from a draft genome sequence of the tobacco hornworm moth, Manduca sexta

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