ALPHA, BETA-I, BETA-II, DELTA, AND EPSILON PROTEIN-KINASE-C ISOFORMS AND COMPOUND ACTIVITY IN THE SCIATIC-NERVE OF NORMAL AND DIABETIC RATE

Defective protein kinase C (PKC) has been implicated in impaired Na+,K +-ATPase activity in the sciatic nerve of streptozotocin-induced diabe tic rats. In the present study, alpha, beta I, beta II, gamma, delta, and epsilon isoform-specific antibodies were used in parallel to the m easurement of compound PKC activity for the characterization of PKC di stribution and isoform expression in sciatic nerves of normal and diab etic rats. To distinguish isoform expression between the axonal and gl ial compartments, PKC isoforms were evaluated in nerves subjected to W allerian degeneration and in a pure primary Schwann cell culture. alph a, beta I, beta II, delta, and epsilon but no gamma isoforms were dete cted in sciatic nerve. Similar immunoreactivity was observed in degene rated nerves 3-4 days after transection except for diminished beta I a nd epsilon species; in Schwann cell cultures, only alpha, beta II, del ta, and epsilon were detected. In normal nerves, two-thirds of PKC com pound activity was found in the cytosol and 50% of total enzyme activi ty translocated to the Na+,K+-ATPase-enriched membrane fraction with p horbol myristate acetate. Similar redistribution patterns were observe d for the immunoreactivity of all isoforms with-the exception of delta , which did not translocate to the membrane with phorbol myristate ace tate. No abnormality in compound PKC activity, in the immunoreactive i ntensity, or in the distribution of PKC isoforms could be detected in rat sciatic nerve after 6-12 weeks of diabetes. Thus, defective activa tion rather than decreased intrinsic PKG activity may occur in diabeti c neuropathy.