AN INCREASE IN PHOSPHORYLATION OF MICROTUBULE-ASSOCIATED PROTEIN-2 ACCOMPANIES DENDRITE EXTENSION DURING THE DIFFERENTIATION OF CULTURED HIPPOCAMPAL-NEURONS

Hippocampal neurones, from embryonic rats, were cultured for different times and the extension of dendrite-like processes was analysed morph ologically and by immunofluorescence, using microtubule-associated pro tein 2 (MAP2) as a marker. Simultaneously, the changes in phosphorylat ion in MAP2 were analyzed and a correlation between dendrite sprouting and an increase in MAP2 phosphorylation was found. Phospho-MAP2 was c leaved by Staphylococcus aureus V8 protease limited proteolysis and it s phosphopeptide pattern was compared to that obtained with two protei n kinases (calcium/calmodulin-dependent kinase and protein kinase C) i n vitro. An involvement of calcium/calmodulin-dependent protein kinase in the phosphorylation of MAP2, occurring simultaneously with dendrit e extension during neuronal differentiation in vitro, is suggested.