PKC IN RAT CORTICAL SYNAPTOSOMES - EFFECTS OF DEPOLARIZATION

PKC isotypes were studied in rat cortical synaptosomes. Resting synapt osomes, subfractionated into cytosolic and particulate (Triton X100-so luble and insoluble) fractions, containing PKC beta(1), gamma, delta a nd epsilon isotypes but very little PKC beta(2) or alpha. PKC gamma an d epsilon were evenly distributed in the cytosolic and particulate fra ctions; PKC beta(1) was mainly in the cytosol (70%) and PKC gamma was primarily particulate (80%). Triton X-100 extracted most of the PKC de lta and epsilon from the particulate fraction but only half of the PKC gamma, indicating PKC gamma association with the cytoskeleton. Follow ing KCl treatment (30 mM), both the classical PKC isotypes beta(1) and gamma shifted from the cytosolic to the particulate fraction, with PK C beta(1) moving specifically to the detergent insoluble fraction wher eas PKC gamma appeared to move to both. It is concluded that PKC beta( 1), gamma, and epsilon isotypes can occur presynaptically and suggeste d that PKC beta(1) and gamma are directly involved in synaptic transmi ssion. Apparent mol. wt changes in translocating forms may be related to phosphorylation and subsynaptosomal location.