PKC in rat cortical synaptosomes: Effects of depolarization

PKC isotypes were studied in rat cortical synaptosomes. Resting synaptosomes, subfractionated into cytosolic and particulate (Triton X100-soluble and insoluble) fractions, containing PKC beta(1), gamma, delta and epsilon isotypes but very little PKC beta(2) or alpha. PKC gamma and epsilon were evenly distributed in the cytosolic and particulate fractions; PKC beta(1) was mainly in the cytosol (70%) and PKC gamma was primarily particulate (80%). Triton X-100 extracted most of the PKC delta and epsilon from the particulate fraction but only half of the PKC gamma, indicating PKC gamma association with the cytoskeleton. Following KCl treatment (30 mM), both the classical PKC isotypes beta(1) and gamma shifted from the cytosolic to the particulate fraction, with PKC beta(1) moving specifically to the detergent insoluble fraction whereas PKC gamma appeared to move to both. It is concluded that PKC beta(1), gamma, and epsilon isotypes can occur presynaptically and suggested that PKC beta(1) and gamma are directly involved in synaptic transmission. Apparent mol. wt changes in translocating forms may be related to phosphorylation and subsynaptosomal location.