Enhanced desensitization followed by unusual resensitization in GABAA receptors in phospholipase C-related catalytically inactive protein-1/2 double-knockout mice
Enhanced desensitization followed by unusual resensitization in GABAA receptors in phospholipase C-related catalytically inactive protein-1/2 double-knockout mice
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DOI：
10.1007/s00424-014-1511-5
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发表时间：
2014-04
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影响因子：
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通讯作者：
H. Toyoda;M. Saito;Hajime Sato;Takuma Tanaka;Takeo Ogawa;H. Yatani;Tsutomu Kawano;T. Kanematsu;M. Hirata;Youngnam Kang
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作者：
H. Toyoda;M. Saito;Hajime Sato;Takuma Tanaka;Takeo Ogawa;H. Yatani;Tsutomu Kawano;T. Kanematsu;M. Hirata;Youngnam Kang
磷脂酶C相关的催化失活蛋白(PRIP-1/2)参与了GABA受体(GABAAR)的膜转运和细胞内钙库的调节。GABAAR介导的电流可受细胞内钙离子的调节。然而，在PRIP-1/2双基因敲除(PRIP-DKO)小鼠中，GABAARs的动力学特性是否受到细胞内钙储存调节的改变仍不清楚。在这里，我们研究了在PRIP-DKO小鼠中，由GABA喷雾引起的桶状皮质第3层(L3)锥体细胞(PC)的GABA电流(IGABA)是否发生改变。PRIP-1/2的缺失增强了IGBA的脱敏作用，但在GABA泡芙偏移量处产生了驼峰样的尾电流(Tail-I)。GABAAR拮抗剂抑制IGABA和驼峰状的尾巴-I。在PRIP-DKO PC中，IGBA和驼峰样Tail-I的脱敏作用是由细胞内钙离子浓度升高所介导的，并可被钙调神经磷酸酶抑制剂和Ru红基本消除。钙成像显示，在PRIP-DKO PC中，钙离子诱导的钙释放(CICR)和随后的商店操作的钙进入(SOCE)比野生型PC更有效。数学模型表明，GABA解离速率的减慢和快速脱敏速率的加快(通过增强其对GABA的浓度依赖性)参与了驼峰状尾巴的产生。这些结果表明，在PRIP-DKO小鼠桶状皮质的L3PC中，由于增强的CICR和SOCE引起的钙调神经磷酸酶活性的增加，增强了GABAARs的脱敏作用，并减缓了GABA解结合的速度，导致了它们在去掉GABA后异常的再敏感。
Phospholipase C-related catalytically inactive proteins (PRIP-1/2) are previously reported to be involved in the membrane trafficking of GABAAreceptor (GABAAR) and the regulation of intracellular Ca2+stores. GABAAR-mediated currents can be regulated by the intracellular Ca2+. However, in PRIP-1/2 double-knockout (PRIP-DKO) mice, it remains unclear whether the kinetic properties of GABAARs are modulated by the altered regulation of intracellular Ca2+stores. Here, we investigated whether GABAAR currents (IGABA) evoked by GABA puff in layer 3 (L3) pyramidal cells (PCs) of the barrel cortex are altered in PRIP-DKO mice. The deletion of PRIP-1/2 enhanced the desensitization of IGABAbut induced a hump-like tail current (tail-I) at the GABA puff offset. IGABAand the hump-like tail-I were suppressed by GABAAR antagonists. The enhanced desensitization of IGABAand the hump-like tail-I in PRIP-DKO PCs were mediated by increases in the intracellular Ca2+concentration and were largely abolished by a calcineurin inhibitor and ruthenium red. Calcium imaging revealed that Ca2+-induced Ca2+release (CICR) and subsequent store-operated Ca2+entry (SOCE) are more potent in PRIP-DKO PCs than in wild-type PCs. A mathematical model revealed that a slowdown of GABA-unbinding rate and an acceleration of fast desensitization rate by enhancing its GABA concentration dependency are involved in the generation of hump-like tail-Is. These results suggest that in L3 PCs of the barrel cortex in PRIP-DKO mice, the increased calcineurin activity due to the potentiated CICR and SOCE enhances the desensitization of GABAARs and slows the GABA-unbinding rate, resulting in their unusual resensitization following removal of GABA.