IP3-independent signalling of OX1 orexin/hypocretin receptors to Ca2+ influx and ERK
IP3-independent signalling of OX1 orexin/hypocretin receptors to Ca2+ influx and ERK
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DOI：
10.1016/j.bbrc.2006.12.045
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发表时间：
2007-02-09
影响因子：
3.1
通讯作者：
Kukkonen, Jyrki P.
中科院分区：
文献类型：
--
作者：
Ekholm, Marie E.;Johansson, Lisa;Kukkonen, Jyrki P.
OXI - orexin受体（OXIR）已被证明激活受体操作的Ca2+内流途径作为其主要信号通路；然而，由于食欲素受体也偶联磷脂酶C，从而与肌醇-1,4,5-三磷酸（IP3）依赖性Ca2+释放，研究受到阻碍。我们在这里设计了一种方法来阻断后一种信号传导，以便专注于重组系统中OXIR激活Ca2+内流的机制。IP3代谢酶IP3-3激酶a（肌醇-1,4,5-三磷酸->肌醇-1,3,4,5-四磷酸肌醇）和I型IP3-5-磷酸酶（肌醇-1,4,5-三磷酸->肌醇-1,4-二磷酸）的瞬时表达几乎完全减弱了oxir刺激的IP3升高和细胞内Ca2+释放。在ip3依赖性信号的衰减后，受体操作的Ca2+内流途径成为Ca2+升高的唯一来源，从而能够对受体-通道耦合进行机制研究。IP3升高的降低不影响oxir介导的ERK（细胞外信号调节激酶）在CHO细胞中的激活，这支持了我们之前的发现，即受体操作的Ca2+内流对这种反应的主要重要性。(c) 2006爱思唯尔公司版权所有。
OXI orexin receptors (OXIR) have been shown to activate receptor-operated Ca2+ influx pathways as their primary signalling pathway; however, investigations are hampered by the fact that orexin receptors also couple to phospholipase C, and therewith inositol-1,4,5-trisphosphate (IP3)-dependent Ca2+ release. We have here devised a method to block the latter signalling in order to focus on the mechanism of Ca2+ influx activation by OXIR in recombinant systems. Transient expression of the IP3-metabolising enzymes IP3-3-kinase-A (inositol-1,4,5-trisphosphate -> inositol-1,3,4,5-tetrakisphosphate) and type I IP3-5-phosphatase (inositol-1,4,5-trisphosphate -> inositol-1,4-bisphosphate) almost completely attenuated the OXIR-stimulated IP3 elevation and Ca2+ release from intracellular stores. Upon attenuation of the IP3-dependent signalling, the receptor-operated Ca2+ influx pathway became the only source for Ca2+ elevation, enabling mechanistic studies on the receptor-channel coupling. Attenuation of the IP3 elevation did not affect the OXIR-mediated ERK (extracellular signal-regulated kinase) activation in CHO cells, which supports our previous finding of the major importance of receptor-operated Ca2+ influx for this response. (c) 2006 Elsevier Inc. All rights reserved.