Caroni P, Schwab M E
Brain Research Institute, University of Zurich, Switzerland.
J Cell Biol. 1988 Apr;106(4):1281-8. doi: 10.1083/jcb.106.4.1281.
Lack of neurite growth in optic nerve explants in vitro has been suggested to be due to nonpermissive substrate properties of higher vertebrate central nervous system (CNS) white matter. We have searched for surface components in CNS white matter, which would prevent neurite growth. CNS, but not peripheral nervous system (PNS) myelin fractions from rat and chick were highly nonpermissive substrates in vitro. We have used an in vitro spreading assay with 3T3 cells to quantify substrate qualities of membrane fractions and of isolated membrane proteins reconstituted in artificial lipid vesicles. CNS myelin nonpermissiveness was abolished by treatment with proteases and was not associated with myelin lipid. Nonpermissive proteins were found to be membrane bound and yielded highly nonpermissive substrates upon reconstitution into liposomes. Size fractionation of myelin protein by SDS-PAGE revealed two highly nonpermissive minor protein fractions of Mr 35 and 250-kD. Removal of 35- and of 250-kD protein fractions yielded a CNS myelin protein fraction with permissive substrate properties. Supplementation of permissive membrane protein fractions (PNS, liver) with low amounts of 35- or of 250-kD CNS myelin protein was sufficient to generate highly nonpermissive substrates. Inhibitory 35- and 250-kD proteins were found to be enriched in CNS white matter and were found in optic nerve cell cultures which contained highly nonpermissive, differentiated oligodendrocytes. The data presented demonstrate the existence of membrane proteins with potent nonpermissive substrate properties. Distribution and properties suggest that these proteins might play a crucial inhibitory role during development and regeneration in CNS white matter.
体外视神经外植体中神经突生长缺乏被认为是由于高等脊椎动物中枢神经系统（CNS）白质的非允许性底物特性所致。我们在CNS白质中寻找了会阻止神经突生长的表面成分。大鼠和鸡的CNS髓磷脂组分而非外周神经系统（PNS）髓磷脂组分在体外是高度非允许性底物。我们使用3T3细胞的体外铺展试验来量化膜组分以及人工脂质小泡中重构的分离膜蛋白的底物质量。蛋白酶处理消除了CNS髓磷脂的非允许性，且其与髓磷脂脂质无关。发现非允许性蛋白是膜结合的，并且在重构到脂质体中后产生高度非允许性底物。通过SDS-PAGE对髓磷脂蛋白进行大小分级分离，揭示了两个Mr为35和250 kD的高度非允许性小蛋白组分。去除35 kD和250 kD蛋白组分后产生具有允许性底物特性的CNS髓磷脂蛋白组分。用少量35 kD或250 kD的CNS髓磷脂蛋白补充允许性膜蛋白组分（PNS、肝脏）足以产生高度非允许性底物。发现抑制性的35 kD和250 kD蛋白在CNS白质中富集，并且在含有高度非允许性、分化的少突胶质细胞的视神经细胞培养物中也能找到。所呈现的数据证明了具有强大非允许性底物特性的膜蛋白的存在。其分布和特性表明这些蛋白可能在CNS白质的发育和再生过程中发挥关键的抑制作用。
