| Primary Identifier | IPR013295 | Type | Family |
| Short Name | MAL |
| description | Myelin is a product of myelinating cells: Schawnn cells in the peripheral nervous system (PNS) and oligodendrocytes in the central nervous system (CNS). The processes of these myelinating cells wrap around axon segments to form a sheath. This sheath possesses insulating properties, allowing rapid propagation of action potentials (the electrical signal propagated by nerve cells) between the myelinating cell intervening nodes. Without myelin insulation, axons would need a 10-30-fold increase in diameter to achieve comparable conduction velocities. At the onset of myelination, during development, large amounts of myelin-specific lipids and proteins are synthesised and transported to the developing myelin sheath. The major protein component of PNS and CNS myelin differs between the 2 nervous systems. However, some of the minor protein components, including the 4 transmembrane (TM)-domain-containing myelin and lymphocyte protein (MAL), are found in both systems. Outside the nervous system, MAL is also found in T-cells and some epithelial cells (e.g., kidney, stomach and thyroid) []. Glycosphingolipids are enriched in both epithelial cells and myelin, and are believed to decrease the permeability of lipid membranes to small molecules and increase the ability for membrane curvature. MAL co-purifies with glycosphingolipids in detergent-insoluble domains, suggesting a possible interaction. In Madin Darby Canine Kidney (MDCK) cells, MAL is found mainly in transport vesicles, and recent studies suggest that MAL is required for efficient vesicular transport of proteins across apical cell membranes []. In myelinating cells, MAL appears to play a similar role, interacting with glycosphingolipids to decrease membrane permeability; however, here this property most likely manifests itself as an improved insulating ability of the myelin []. In lymphocytes, however, MAL appears to act as a TM-linker protein in T-cell signal transduction, linking the cell surface glycosyl phosphatidylinositol anchored protein CD59 to the intracellular tyrosine kinase Lck []. |
