Functional glycoproteins expressed in Schwann cell membrane.

Certain types of glycoproteins expressed in Schwann cell appear to play specific roles in neurite growth and neural migration. Peripheral myelin protein-22 (PMP-22) is a glycoprotein down-regulated in nerve damage and is involved in both trembler mouse mutation and human Charcot-Marie-Tooth disease, type 1A. PMP-22 now appears to be a homologue of previously reported PASII. The homology of PASII/PMP-22 to the growth arrest-specific protein (Gas-3) suggests its role in Schwann cell development. P0, a major protein in peripheral myelin, mediates cell adhesion and promotes neurite outgrowth. In cell adhesion mediated by P0, its unique carbohydrate chain plays an important role. A special isoform of L1 (L1cs), with a short deletion in the intracellular domain, is localized in Schwann cells, whilst the complete L1 is exclusively located in neurons. L1cs in Schwann cells may function differently from L1 in neurons.