Zuber M X, Strittmatter S M, Fishman M C
Developmental Biology Laboratory, Massachusetts General Hospital Cancer Center, Boston 02114.
Nature. 1989 Sep 28;341(6240):345-8. doi: 10.1038/341345a0.
Neurons and other cells, such as those of epithelia, accumulate particular proteins in spatially discrete domains of the plasma membrane. This enrichment is probably important for localization of function, but it is not clear how it is accomplished. One proposal for epithelial cells is that proteins contain targeting signals which guide preferential accumulation in basal or apical membranes. The growth-cone membrane of a neuron serves as a specialized transduction system, which helps to convert cues from its environment into regulated growth. Because it can be physically separated from the cell soma, it has been possible to show that the growth-cone membrane contains a restricted set of total cellular proteins, although, to our knowledge, no proteins are limited to that structure. One of the most prominent proteins in the growth-cone membrane is GAP-43. Basi et al. have suggested that the N-terminus of GAP-43 might be important for the binding of GAP-43 to the growth-cone membrane. Skene and Virag recently found that the cysteines in the N-terminus are fatty-acylated and that this post-translational modification correlates with membrane-binding ability. We investigated the binding of GAP-43 to the growth-cone membrane by mutational analysis and by laser-scanning confocal microscopy of fusion proteins that included regions of GAP-43 and chloramphenicol acetyltransferase (CAT). We found that a short stretch of the GAP-43 N-terminus suffices to direct accumulation in growth-cone membranes, especially in the filopodia. This supports a previous proposal for the importance of this region of GAP-43 in determining the membrane distribution of GAP-43.
神经元和其他细胞，如上皮细胞，会在质膜的空间离散区域积累特定蛋白质。这种富集可能对功能定位很重要，但尚不清楚其实现方式。对于上皮细胞的一种观点是，蛋白质含有靶向信号，可引导其优先在基底膜或顶膜中积累。神经元的生长锥膜是一种特殊的转导系统，有助于将来自其环境的线索转化为受控生长。由于它可以与细胞体物理分离，因此已证明生长锥膜包含一组有限的总细胞蛋白质，尽管据我们所知，没有蛋白质仅限于该结构。生长锥膜中最突出的蛋白质之一是GAP - 43。巴西等人提出，GAP - 43的N端可能对GAP - 43与生长锥膜的结合很重要。斯基恩和维拉克最近发现，N端的半胱氨酸被脂肪酸酰化，这种翻译后修饰与膜结合能力相关。我们通过突变分析和对包含GAP - 43区域和氯霉素乙酰转移酶（CAT）的融合蛋白进行激光扫描共聚焦显微镜研究，来研究GAP - 43与生长锥膜的结合。我们发现，GAP - 43 N端的一小段就足以指导其在生长锥膜中积累，尤其是在丝状伪足中。这支持了之前关于GAP - 43这一区域在决定GAP - 43膜分布方面重要性的提议。
