Functional analysis of Ras-like small GTPase protein Rig in neural cells.

新发现的ras样GTPase小蛋白Rig在神经细胞中显著表达，并具有膜结合所需的c端CAAX戊酰化基序。尽管Rig与Ras具有高度的序列同一性，但其在神经细胞中的生理功能仍有待阐明。我们发现过表达的Rig蛋白与转铁蛋白和Rab11共定位，Rab11是循环内体的标记蛋白。虽然转铁蛋白的再循环动力学似乎与GTP或gdp结合的Rig突变蛋白过表达无关，但preylylation缺失的Rig突变蛋白诱导了再循环动力学的减慢。当这种前置酰化缺陷突变蛋白在原代培养的小鼠海马神经元中过表达时，树突比野生型蛋白表达细胞的树突更少。此外，我们通过下拉方法确定了Rig蛋白的候选结合伙伴，以阐明Rig蛋白的生理作用，如调节循环膜运输和神经细胞的细胞形态发生。

The newly discovered Ras-like small GTPase protein Rig is expressed prominently in neural cells and has a C-terminal CAAX prenylation motif required for membrane association. Although Rig shares high sequence identity with Ras, its physiological functions in neural cells have remained to be clarified. We have found that overexpressed Rig protein was colocalized with transferrin and with Rab11, a marker protein of recycling endosomes. Although the recycling kinetics of transferrin seemed to be indifferent to overexpressed either GTP or GDP-bound Rig mutant protein, the prenylation-deficient Rig mutant protein induced slowing down of the recycling kinetics. When this prenylation-deficient mutant protein was overexpressed in primary-cultured mouse hippocampal neurons, dendrites had fewer arborizations than those of wild type protein-expressed cells. Furthermore, we have identified binding partner candidates of Rig protein by pull down methods to clarify the physiological roles of Rig protein, such as the regulation of recycling membrane traffics and the cellular morphogenesis of neural cells.