Hiley Emma, McMullan Rachel, Nurrish Stephen J
MRC Cell Biology Unit, MRC Laboratory for Molecular Cell Biology, University College London, Gower Sttreet, London, UK.
EMBO J. 2006 Dec 13;25(24):5884-95. doi: 10.1038/sj.emboj.7601458. Epub 2006 Nov 30.
In Caenorhabditis elegans adults, the single Rho GTPase orthologue, RHO-1, stimulates neurotransmitter release at synapses. We show that one of the pathways acting upstream of RHO-1 in acetylcholine (ACh)-releasing motor neurons depends on Galpha12 (GPA-12), which acts via the single C. elegans RGS RhoGEF (RHGF-1). Activated GPA-12 has the same effect as activated RHO-1, inducing the accumulation of diacylglycerol and the neuromodulator UNC-13 at release sites, and increased ACh release. We showed previously that RHO-1 stimulates ACh release by two separate pathways-one that requires UNC-13 and a second that does not. We show here that a non-DAG-binding-UNC-13 mutant that partially blocks increased ACh release by activated RHO-1 completely blocks increased ACh release by activated GPA-12. Thus, the upstream GPA-12/RHGF-1 pathway stimulates only a subset of RHO-1 downstream effectors, suggesting that either the RHO-1 effectors require different levels of activated RHO-1 for activation or there are two distinct pools of RHO-1 within C. elegans neurons.
在秀丽隐杆线虫成虫中,唯一的Rho GTP酶同源物RHO-1可刺激突触处的神经递质释放。我们发现,在释放乙酰胆碱(ACh)的运动神经元中,作用于RHO-1上游的一条信号通路依赖于Gα12(GPA-12),它通过秀丽隐杆线虫唯一的RGS Rho鸟嘌呤核苷酸交换因子(RHGF-1)发挥作用。活化的GPA-12与活化的RHO-1具有相同的作用,可诱导二酰基甘油和神经调质UNC-13在释放位点积累,并增加ACh释放。我们之前表明,RHO-1通过两条独立的信号通路刺激ACh释放——一条需要UNC-13,另一条则不需要。我们在此表明,一个非二酰基甘油结合的UNC-13突变体可部分阻断活化的RHO-1增加ACh释放的作用,而该突变体可完全阻断活化的GPA-12增加ACh释放的作用。因此,上游的GPA-12/RHGF-1信号通路仅刺激RHO-1下游效应器的一个子集,这表明要么RHO-1效应器激活需要不同水平的活化RHO-1,要么秀丽隐杆线虫神经元内存在两个不同的RHO-1池。