Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Genes Cells. 2014 Feb;19(2):97-111. doi: 10.1111/gtc.12109. Epub 2013 Nov 20.
Protrudin is a membrane protein that regulates polarized vesicular transport. Now, we have identified a novel isoform of protrudin (protrudin-L) that contains an additional seven amino acids between the FFAT motif and the coiled-coil domain compared with the conventional isoform (protrudin-S) as a result of alternative splicing of a microexon (exon L). Protrudin-L mRNA was found to be mostly restricted to the central nervous system in mice, whereas protrudin-S mRNA was detected in all tissues examined. With the use of a splicing reporter minigene that produces two distinct fluorescent proteins in a manner dependent on the splicing pattern of protrudin transcripts, we found that most neurons express protrudin-L, whereas astrocytes express both protrudin isoforms and oligodendrocytes express only protrudin-S. Protrudin-L associated to a greater extent with vesicle-associated membrane protein-associated protein (VAP) than protrudin-S. Expression of protrudin-L in hippocampal neurons of protrudin-deficient mice also promoted neurite outgrowth more efficiently than protrudin-S. Our results suggest that protrudin-L is a neuron-specific protrudin isoform that promotes axonal elongation and contributes to the establishment of neuronal polarity.
蛋白 protrudin 是一种调节极化囊泡运输的膜蛋白。现在，我们通过对微外显子（exon L）的选择性剪接，发现了一种新型的 protrudin 异构体（protrudin-L），与传统异构体（protrudin-S）相比，其在 FFAT 基序和螺旋卷曲结构域之间额外含有七个氨基酸残基。在小鼠中，protrudin-L mRNA 主要局限于中枢神经系统，而 protrudin-S mRNA 则存在于所有检测到的组织中。利用一种拼接报告基因 minigene，该基因以依赖于 protrudin 转录本拼接模式的方式产生两种不同的荧光蛋白，我们发现大多数神经元表达 protrudin-L，而星形胶质细胞表达两种 protrudin 异构体，少突胶质细胞仅表达 protrudin-S。与 protrudin-S 相比，protrudin-L 与囊泡相关膜蛋白相关蛋白（VAP）的结合程度更高。在 protrudin 缺失型小鼠的海马神经元中表达 protrudin-L 也比 protrudin-S 更有效地促进轴突生长。我们的结果表明，protrudin-L 是一种神经元特异性的 protrudin 异构体，它可以促进轴突伸长，并有助于建立神经元极性。
