Tetraspanin-7 regulation of L-type voltage-dependent calcium channels controls pancreatic β-cell insulin secretion.
Tetraspanin-7 regulation of L-type voltage-dependent calcium channels controls pancreatic β-cell insulin secretion.
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DOI：
10.1113/jp279941
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发表时间：
2020-11
期刊：
影响因子：
--
通讯作者：
Jacobson DA
中科院分区：
文献类型：
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作者：
Dickerson MT;Dadi PK;Butterworth RB;Nakhe AY;Graff SM;Zaborska KE;Schaub CM;Jacobson DA
葡萄糖刺激的胰岛素分泌是由钙离子通过电压依赖性钙离子通道进入胰腺β-细胞调节的。TSPAN(TSPAN)跨膜蛋白控制着钙离子的转运，因此也可能调节GSIS。TSPAN-7是含量最丰富的胰岛，免疫组织化学染色显示TSPAN-7在β-和α-细胞中高表达，但其功能尚未确定。在这里，我们发现TSPAN-7基因敲除(KD)增加了葡萄糖刺激的钙离子内流到小鼠和人的β-细胞。此外，TSPAN-7KD还可使小鼠β细胞钙振荡频率加快。由于TSPAN-7 KD在去极化钳制膜电位时也能促进钙内流，因此我们观察了TSPAN-7对Cav通道活动的影响。TSPAN-7KD增强小鼠和人β细胞的L型钙通道电流。相反，TSPAN-7与CaV1.2和CaV1.3 L型Cav通道的异源表达减少了Cav电流，减少了钙离子通过这两个通道的内流。这可能是TSPAN-7和L型CAV通道直接相互作用的结果，因为TSPAN-7与来自原代人β细胞的CaV1.2和CaV1.3以及来自异源表达系统的CAV1.2和CaV1.3免疫共沉淀。人β-细胞TSPAN-7KD促进基础(5.6mM葡萄糖)和刺激(45mMKCl+14 mM葡萄糖)胰岛素分泌。这些发现有力地表明，TSPAN-7对β-细胞L型钙离子通道的调节是β-细胞葡萄糖刺激钙内流的关键决定因素，因此是GSIS的设定点。
Glucose-stimulated insulin secretion (GSIS) is regulated by calcium (Ca2+) entry into pancreatic β-cells through voltage-dependent Ca2+ (CaV) channels. Tetraspanin (TSPAN) transmembrane proteins control Ca2+ handling, and thus they may also modulate GSIS. TSPAN-7 is the most abundant islet TSPAN and immunostaining of mouse and human pancreatic slices shows that TSPAN-7 is highly expressed in β- and α-cells; however, the function of islet TSPAN-7 has not been determined. Here, we show that TSPAN-7 knockdown (KD) increases glucose-stimulated Ca2+ influx into mouse and human β-cells. Additionally, mouse β-cell Ca2+ oscillation frequency was accelerated by TSPAN-7 KD. Because TSPAN-7 KD also enhanced Ca2+ entry when membrane potential was clamped with depolarization, the effect of TSPAN-7 on CaV channel activity was examined. TSPAN-7 KD enhanced L-type CaV currents in mouse and human β-cells. Conversely, heterologous expression of TSPAN-7 with CaV1.2 and CaV1.3 L-type CaV channels decreased CaV currents and reduced Ca2+ influx through both channels. This was presumably the result of a direct interaction of TSPAN-7 and L-type CaV channels because TSPAN-7 coimmunoprecipitated with both CaV1.2 and CaV1.3 from primary human β-cells and from a heterologous expression system. Finally, TSPAN-7 KD in human β-cells increased basal (5.6 mM glucose) and stimulated (45 mM KCl + 14 mM glucose) insulin secretion. These findings strongly suggest that TSPAN-7 modulation of β-cell L-type CaV channels is a key determinant of β-cell glucose-stimulated Ca2+ entry and thus the set-point of GSIS.