Identification and analysis of factors that regulate cell surface expression of G-protein coupled receptor

已知γ-氨基丁酸（GABA）作为中枢和外周神经系统的抑制性神经递质。GABA受体分为两类：一类是离子型受体（GABA_A和GABA_C），另一类是代谢型G蛋白偶联受体（GABA_B）。GABA_B受体作为一种GABA_2受体于1997年被克隆出来<B1>，此后，大量的工作集中在克隆的GABA_B受体的异源功能表达上。然而，没有一个表达研究是成功的。因此，表达研究的失败提示我们存在一些额外的蛋白质用于GABA_B受体的功能表达。我们先前已经报道了功能性GABA_B受体实际上在表达大量表达GABA_B受体的大鼠脑poly（A）^+ RNA的爪蟾卵母细胞中表达（Uezono等人，生物化学生物物理学通信资源241：476-（1997）; Uezono等人，NeuroReport 9：583-（1998））。W ...更多信息 因此，我们决定用同时表达大鼠poly（A）^+ RNA和克隆的GABA_受体的卵母细胞克隆“GABA_B受体表达因子”<B1>。在这一实验过程中，1998年底，其他人证明了GABA_受体<B1>和新克隆的GABA_<B2>受体的异源多聚化是GABA_B受体功能表达所必需的。因此，我们改变了想法，用克隆的GABA_受体和GABA_受体来研究GABA_B受体异源多聚化的机制<B2><B2>。与此同时，另一种代谢受体肾上腺髓质素受体（adrenomedullin receptor，AR）与降钙素受体样受体（calcitonin receptor-like receptor，CRLR）和小分子受体活性修饰蛋白（receptor-activity-modifying proteins，RAMPs）形成复合物发挥功能。我们利用肾上腺髓质素受体（CRLR和RAMP）的优势，比较了肾上腺髓质素受体和GABA_B受体的形成机制，并希望能进一步阐明GABA_B受体的形成机制以及GABA_B受体功能表达需要异源多聚体的原因。

γ-Amino butyric acids (GABA) is known to act as an inhibitory neurotransmitter on the central and peripheral nervous system. Receptors for GABA are divided into two types : one belongs to ionotropic receptors (GABA_A and GABA_C) and another belongs to metabotoropic G-protein coupled receptors (GABA_B). GABA_B receptor has been cloned in 1997 as a GABA_<B1> receptor and since then, a lot of works have been focused on the heterologous functional expression of the cloned GABA_B receptors. However, none of the expression study has succeeded. Accodingly the failure of the expression study suggested us the existence of some additional protein (s) for the functional expression of GABA_B receptors. We have previously reported that functional GABA_B receptors are actually expressed in Xenopus oocytes expressing the rat brain poly(A)^+ RNA which abundantly express the GABA_B receptor (Uezono et al., Biochem. Biophys. Res. Commun. 241 : 476- (1997) ; Uezono et al., NeuroReport 9 : 583- (1998)). W … More e therefore determined to clone the 'GABA_B receptor expressing factor (s)' with the oocytes expressing both the rat poly(A)^+ RNA and cloned GABA_<B1> receptor.In the course of such experiments, others have demonstrated in late 1998 that heteromultimerization of GABA_<B1> and newly cloned GABA_<B2> receptors are required for functional expression of GABA_B receptors.So we have changed our mind to investigate the mechanism of how GABA_B receptors are required heteromultimerization to be functional, with the cloned GABA_<B2> and GABA_<B2> receptors. In the mean time, another type of metabotoropic receptor namely adrenomedullin receptor is found to form complex with calcitonin receptor-like receptor (CRLR) and small proteins called 'receptor-activity-modifying proteins (RAMPs)' to be functional. We then took advantage of adrenomedullin receptors (CRLR and RAMPs) and compared the mechanism of adrenomedullin receptor formation with that of GABA_B receptor formation.We are still in progress of our study and hope to continue to clarify the mechanism how GABA_B receptors are formed and why GABA_B receptors are required to be heteromultimer for their functional expression Less