Phosphorylation and Proteolytic Degradation of Neurofilaments

Abstract

Phosphorylation of neurofilaments (NFs) by endogenous kinases in the presence of various protein kinase inhibitors was examined. Staurosporin (an inhibitor of protein kinase C and src kinase), PK-I (an inhibitor of protein kinase A) and an inhibitor peptide for p34 kinase had little or no effect on endogenous phosphorylation. However, heparin at 100 µg/ml inhibited and polylysine at 20 µg/ml markedly stimulated endogenous phosphorylation, suggesting a possible role of protein kinase P in NF phosphorylation. Phosphorylation of NFs by either protein kinase C or protein kinase P protected partially against proteolytic digestion by trypsin or cathepsin L.