Regulation of heart insulin receptor tyrosine kinase activity by magnesium and spermine |
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Authors: | Ralph Paxton Lingxiang Ye |
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Institution: | (1) Dept. Anat., Physiol. & Pharmacol., Laboratory of Metabolic Disorders, Auburn University, Auburn, AL, 36849, U.S.A. |
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Abstract: | Insulin action and aspects of the insulin-signaling pathway have been studied in the heart although the direct regulation of the heart’s insulin receptor has not been explored. This study describes the first purification and characterization of the mammalian (rabbit, rat and bovine) heart insulin receptor. The rabbit heart IR showed maximum insulin binding of 18 μg/mg (~1 mole insulin/mole (α2β2) receptor) and a curvilinear Scatchard plot with a high affinity KD for insulin binding of ~4 nM at optimal pH (7.8) and NaCl concentration (150 mM). The insulin receptor tyrosine kinase activity was stimulated by insulin, Mg2+ (half-maximum response at ~5.6–10.6 nM and ~8.5 mM, respectively) and by the physiological polyamines, spermine and spermidine. The stimulation by Mg2+ and the polyamines occurred with and without insulin. These characteristics of the heart insulin receptor provide a mechanism for regulating the activity of the receptor’s tyrosine kinase activity by the intracellular free Mg2+ concentration and the polyamines in the absence and presence of insulin. |
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Keywords: | heart insulin receptor insulin receptor tyrosine kinase magnesium polyamines spermine spermidine myocardial ischemia diabetes mellitus |
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