Open AccessHyperammonemia decreases protein‐kinase‐C‐dependent phosphorylation of microtubule‐associated protein 2 and increases its binding to tubulin
Author(s) -
FELIPO Vicente,
GRAU Eugenio,
MIÑANA MaríaDolores,
GRISOLÍA Santiago
Publication year - 1993
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1993.tb17917.x
Subject(s) - microtubule , tubulin , phosphorylation , cytosol , biology , kinase , microtubule associated protein , hyperammonemia , protein kinase a , microbiology and biotechnology , protein phosphorylation , biochemistry , medicine , enzyme
Hyperammonemia increases the polymerization of brain microtubules, which is controlled by the binding of microtubule‐associated protein (MAP) 2; binding of MAP‐2 is, in turn, regulated by phosphorylation. We have found that the binding of MAP‐2 to tubulin is greatly increased by hyperammonemia, however, the brain content of MAP‐2 is not affected. Microtubules isolated from hyperammonemic rats contained approximately twice the MAP‐2/mg microtubular protein that of microtubules isolated from control animals. MAP isolated from brain microtubules of hyperammonemic rats stimulated the polymerization of tubulin more than MAP isolated from control animals. This appears to be due to the increased content of MAP‐2. In vitro phosphorylation, using brain homogenates, showed that protein‐kinase‐C‐dependent phosphorylation of MAP‐2 was markedly decreased in hyperammonemic rats. Hyperammonemia also affected the intracellular distribution of brain protein kinase C; its content in the cytosol increased about 23%, while in membranes it decreased by 46%. The possible role of decreased protein‐kinase‐C‐dependent phosphorylation on the increased binding of MAP‐2 to tubulin and in the increased polymerization of microtubules in the brain of hyperammonemic rats is discussed.