Heuss D, Schlötzer-Schrehardt U
Department of Neurology, Friedrich Alexander University of Erlangen-Nuremberg, Germany.
Neurol Res. 1998 Jun;20(4):360-4.
Phosphoprotein B-50, also termed growth-associated protein GAP43, is a membrane-bound phosphoprotein expressed in neurons. It is particularly abundant during periods of axonal outgrowth in development and regeneration of the central and peripheral nervous systems. Recently the expression of phosphoprotein B-50 in regenerating muscle fibers was reported and it was assumed that phosphoprotein B-50, in muscles, plays a role in the determination of the growth morphology of regenerating muscle fibers. Thus, phosphoprotein B-50 no longer can be regarded as a neuron-specific molecule. In this paper we study the subcellular localization of phosphoprotein B-50 in regenerating human skeletal muscle fibers by electron immunohistochemistry. Phosphoprotein B-50 immunoreactivity is randomly distributed over the nuclear and perinuclear area of regenerating muscle fibers. Previously, by light-microscopy phosphoprotein B-50 immunoreactivity was demonstrated on the inner face of the sarcolemma in hypotrophic type 1 fibers in congenital fiber type disproportion. It is this distribution of phosphoprotein B-50 in developmentally disordered myocytes in particular which allows an analogy to the corresponding results found for growing axons. But we did not find subsarcolemmal expression of B-50 in regenerating muscle fibers. Probably this indicates that there is a difference in B-50 expression between regeneration of muscle fibers and developmentally retarded/immature myofibers. The presented data suggest that phosphoprotein B-50 is inserted only stage-dependent in the extending sarcolemma of the growing muscle fiber. Analogously to the nervous system, phosphoprotein B-50 may serve a local function involving transmembrane signalling by means of calmodulin binding of phosphoprotein B-50 and/or phosphoprotein B-50 phosphorylation and dephosphorylation.
磷蛋白B - 50，也被称为生长相关蛋白GAP43，是一种在神经元中表达的膜结合磷蛋白。在中枢和外周神经系统发育及再生过程中的轴突生长阶段，它尤其丰富。最近有报道称磷蛋白B - 50在再生肌纤维中表达，并且推测磷蛋白B - 50在肌肉中对再生肌纤维生长形态的确定起作用。因此，磷蛋白B - 50不再能被视为神经元特异性分子。在本文中，我们通过电子免疫组织化学研究了磷蛋白B - 50在再生人骨骼肌纤维中的亚细胞定位。磷蛋白B - 50免疫反应性随机分布于再生肌纤维的核区和核周区域。此前，通过光学显微镜在先天性纤维类型不均衡的营养不良1型纤维的肌膜内表面证实了磷蛋白B - 50免疫反应性。尤其是磷蛋白B - 50在发育异常的肌细胞中的这种分布，使得与生长轴突的相应结果具有相似性。但我们在再生肌纤维中未发现B - 50在肌膜下的表达。这可能表明肌纤维再生与发育迟缓/未成熟肌纤维之间在B - 50表达上存在差异。所呈现的数据表明，磷蛋白B - 50仅在生长肌纤维延伸的肌膜中呈阶段依赖性插入。与神经系统类似，磷蛋白B - 50可能通过磷蛋白B - 50与钙调蛋白的结合和/或磷蛋白B - 50的磷酸化和去磷酸化来发挥涉及跨膜信号传导的局部功能。
