Effects of calcium and cobalt ions on the transfer of proteins to the myelin membrane.
The presence of calcium dependent, cobalt sensitive steps in the transport of proteins to myelin was studied using slices obtained from the brains of 20 day old Wistar rats. When 0.18 mM cobalt chloride was added to the incubation medium, although protein synthesis in the total homogenate was not affected, the entry of labeled PLP into myelin and fraction SN(4) (a myelin related membrane), decreased to 20% of control values. Transport of basic and Wolfgram proteins was not affected by cobalt ions. Similar results were obtained when slices were incubated in a calcium-free medium or in a calcium free medium containing cobalt chloride. The entry of fucose labeled glycoproteins into myelin, which followed a pattern similar to that of PLP, was also inhibited by the presence of cobalt in the incubation medium. These results indicate that the delivery of PLP and glycoproteins on the one hand and of the other myelin proteins on the other is regulated by different mechanisms and that calcium-dependent, cobalt-sensitive steps are involved in the transfer of the former. Acylation of myelin PLP, assayed by the incorporation of palmitic acid, was not influenced by the presence of cobalt chloride in the incubation medium, suggesting that this posttranscriptional event ocurrs close to myelin or in the myelin membrane itself.
Pasquini
J M
JM
Departamento de Química Biológica, Facultad de Farmacia y Bioquimica, Universidad de Buenos Aires and Programa de Investigaciones en Neuroquìmica (PRINEUQUI), CONICET, Junin 956, 1113 Buenos Aires, Argentina.
Bizzozero
O A
OA
Besio Moreno
M
M
Soto
E F
EF