Ontogenetic changes in the level and subcellular distribution of protein kinase C in cat visual cortex

Ontogenetic changes of the total activity and the subcellular distribution of Ca2+-activated, phospholipid-dependent protein kinase (protein kinase C) were investigated in the cat visual cortex. Following homogenization of the tissue in Ca2+-free buffer and separation of membrane-bound and soluble protein kinase C, the enzyme was partially purified by diethylaminoethyl-cellulose chromatography. Total, membrane-bound and soluble enzyme activity were determined by measuring the phosphate incorporation into lysine-rich histone, a substrate for protein kinase C. It was found that the total activity level, while being low in the first 4 weeks, increased rapidly to peak values at 5 weeks of age and declined slightly thereafter. Although at all developmental stages most of the enzyme was recovered in the soluble fraction, the membrane-bound activity exhibited a considerable increase at 5 weeks of age, reflecting a relative shift of protein kinase C from the cytosol to the membranes. The increase and redistribution of protein kinase C activity coincide in time with the developmental phase during which the visual cortex is particularly susceptible to undergo use-dependent modifications. This finding is compatible with the hypothesis that protein kinase C-mediated phosphorylation processes are involved in activity-dependent modifications of neuronal transmission.