Pontier Stéphanie M, Lahaie Nicolas, Ginham Rachel, St-Gelais Fannie, Bonin Hélène, Bell David J, Flynn Helen, Trudeau Louis-Eric, McIlhinney Jeffrey, White Julia H, Bouvier Michel
Département de Biochimie and Groupe de Recherche Universitaire sur le Médicament, Institut de recherche en immunologie et Cancérologie, Université de Montréal, Montréal, Qc, Canada.
EMBO J. 2006 Jun 21;25(12):2698-709. doi: 10.1038/sj.emboj.7601157. Epub 2006 May 25.
The obligatory heterodimerization of the GABAB receptor (GBR) raises fundamental questions about molecular mechanisms controlling its signaling efficacy. Here, we show that NEM sensitive fusion (NSF) protein interacts directly with the GBR heterodimer both in rat brain synaptosomes and in CHO cells, forming a ternary complex that can be regulated by agonist stimulation. Inhibition of NSF binding with a peptide derived from GBR2 (TAT-Pep-27) did not affect basal signaling activity but almost completely abolished agonist-promoted GBR desensitization in both CHO cells and hippocampal slices. Taken with the role of PKC in the desensitization process, our observation that TAT-Pep-27 prevented both agonist-promoted recruitment of PKC and receptor phosphorylation suggests that NSF is a priming factor required for GBR desensitization. Given that GBR desensitization does not involve receptor internalization, the NSF/PKC coordinated action revealed herein suggests that NSF can regulate GPCR signalling efficacy independently of its role in membrane trafficking. The functional interaction between three bona fide regulators of neurotransmitter release, such as GBR, NSF and PKC, could shed new light on the modulation of presynaptic GBR action.
GABAB受体（GBR）的 obligatory 异源二聚化引发了关于控制其信号传导效率的分子机制的基本问题。在这里，我们表明NEM敏感融合（NSF）蛋白在大鼠脑突触体和CHO细胞中都直接与GBR异源二聚体相互作用，形成一种三元复合物，该复合物可受激动剂刺激调节。用源自GBR2的肽（TAT-Pep-27）抑制NSF结合并不影响基础信号活性，但几乎完全消除了CHO细胞和海马切片中激动剂促进的GBR脱敏。结合PKC在脱敏过程中的作用，我们观察到TAT-Pep-27阻止了激动剂促进的PKC募集和受体磷酸化，这表明NSF是GBR脱敏所需的启动因子。鉴于GBR脱敏不涉及受体内化，本文揭示的NSF/PKC协同作用表明NSF可以独立于其在膜运输中的作用来调节GPCR信号传导效率。三种真正的神经递质释放调节剂（如GBR、NSF和PKC）之间的功能相互作用可能为突触前GBR作用的调节提供新的线索。
