Expression of the microtubule-associated protein STOP in oligodendrocytes.

MAURICIO R. GALIANO; SOTO E.F.; PASQUINI J.M.; MARTA E. HALLAK

Palm Beach

Congreso; 33rd Annual Meeting of the American Society for Neurochemistry; 2002

American Society for Neurochemistry

The STOP protein (stable tubule-only polypeptide) is a calmodulin-regulated protein which associates with microtubules and induces cold stabilization. There are different isoforms of this protein that arise from alternative splicing of STOP mRNA. Neurons express two major variants N-STOP (125 kDa) and E-STOP (84 kDa). NIH 3T3 fibroblasts contain a major F-STOP isoform (42 kDa) and two minor STOP variants (48 and 89 kDa). Previously, we demonstrated the presence of N-STOP in the cytoskeleton associated with myelin. Since this protein was only described as a neuronal protein we decided to further investigate the expression of this protein in oligodendrocyte cultures from newborn rat brains. The analysis of the STOP protein expression during oligodendrocyte development, using specific markers (A2B5, O4, and O1), shows that STOP protein is expressed in the soma and processes of oligodendrocyte precursors, immature and mature oligodendrocytes. In addition, we found that MBP has a high colocalization with STOP protein. By Western blot analysis, it was found that these cells express a major STOP variant (89 kDa) and two minor STOP variants of lower molecular weight, similar to fibroblast expression but not the N-STOP (125 kDa). We chose to call the oligodendrocyte major variant O-STOP. When the cultures were exposed to cold temperature we found that O-STOP associates with microtubules and induces microtubule cold stabilization. Under these experimental conditions, we found that MBP associates with microtubules too, and maintains its colocalization with O-STOP protein. At present, we are doing new assays directed to further characterize O-STOP protein and to elucidate how this protein participates in the formation of  myelin by oligodendrocytes. Supported by: SECyT-UNC, Ministerio de Salud de la Nación.