Hamming Kevin S C, Riedel Michael J, Soliman Daniel, Matemisz Laura C, Webster Nicola J, Searle Gavin J, MacDonald Patrick E, Light Peter E
Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
Mol Endocrinol. 2008 Oct;22(10):2293-306. doi: 10.1210/me.2008-0053. Epub 2008 Jul 17.
The sodium-calcium exchanger isoform 1 (NCX1) is intimately involved in the regulation of calcium (Ca(2+)) homeostasis in many tissues including excitation-secretion coupling in pancreatic beta-cells. Our group has previously found that intracellular long-chain acyl-coenzyme As (acyl CoAs) are potent regulators of the cardiac NCX1.1 splice variant. Despite this, little is known about the biophysical properties of beta-cell NCX1 splice variants and the effects of intracellular modulators on their important physiological function in health and disease. Here, we show that the forward-mode activity of beta-cell NCX1 splice variants is differentially modulated by acyl-CoAs and is dependent both upon the intrinsic biophysical properties of the particular NCX1 splice variant as well as the side chain length and degree of saturation of the acyl-CoA moiety. Notably, saturated long-chain acyl-CoAs increased both peak and total NCX1 activity, whereas polyunsaturated long-chain acyl-CoAs did not show this effect. Furthermore, we have identified the exon within the alternative splicing region that bestows sensitivity to acyl-CoAs. We conclude that the physiologically relevant forward-mode activity of NCX1 splice variants expressed in the pancreatic beta-cell are sensitive to acyl-CoAs of different saturation and alterations in intracellular acyl-CoA levels may ultimately lead to defects in Ca(2+)-mediated exocytosis and insulin secretion.
钠钙交换体同工型1（NCX1）密切参与许多组织中钙（Ca(2+)）稳态的调节，包括胰腺β细胞中的兴奋-分泌偶联。我们小组之前发现细胞内长链酰基辅酶A（酰基辅酶A）是心脏NCX1.1剪接变体的有效调节剂。尽管如此，关于β细胞NCX1剪接变体的生物物理特性以及细胞内调节剂对其在健康和疾病中的重要生理功能的影响，人们知之甚少。在这里，我们表明β细胞NCX1剪接变体的正向模式活性受到酰基辅酶A的差异调节，并且既取决于特定NCX1剪接变体的内在生物物理特性，也取决于酰基辅酶A部分的侧链长度和饱和度。值得注意的是，饱和长链酰基辅酶A增加了NCX1的峰值活性和总活性，而多不饱和长链酰基辅酶A则没有这种作用。此外，我们已经确定了可变剪接区域内赋予对酰基辅酶A敏感性的外显子。我们得出结论，胰腺β细胞中表达的NCX1剪接变体的生理相关正向模式活性对不同饱和度的酰基辅酶A敏感，细胞内酰基辅酶A水平的改变最终可能导致Ca(2+)介导的胞吐作用和胰岛素分泌缺陷。
