Protein kinase C subspecies in rabbit corneai epithelium: increased activity of $aL subspecies during wound healing

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Abstract
Protein kinase C (PKC) has been implicated in cell proliferation and differentiation. Multiple forms of PKC have been isolated, principally from the brain where PKC is most abundant. In rabbit corneai epithelium, two distinct major peaks of PKC activity were resolved by hydroxyapatite column chromatography. Peak 2, with 65% of the total PKC activity, corresponds to $aL-PKC, based on its mobility in the column and Western blot analysis using specific monoclonal antibodies. Peak 1 did not react with either polyclonal or monoclonal antibodies to PKC $aL-, β-, and γ-isoforms suggesting the presence of isoforms specific to the corneai epithelium, or of another member of the PKC family. To investigate possible changes in the amounts of the various PKC subspecies during wound healing, the enzyme activities of the isolated subspecies were assayed 2, 5, and 7 days after corneai de-epithelialization. Two days after wounding, by which time the migratory limbal epithelium had covered the denuded area, total PKC activity was unchanged but $aL-PKC activity had increased to 77% of the total activity, compared with 65% in nonwounded epithelium. An increased proportion of $aL-PKC activity was also observed 5 and 7 days after wounding, during which time proliferation of epithelium continued. We hypothesize that $aL-PKC plays a role in long-term responses after injury such as gene expression and corneai epithelial proliferation. Moreover, these studies indicate that the cornea provides a good model of in vivo wound healing for PKC studies.