The occurrence of protein kinase C ? and λ isoforms in retina of different species

The localization and immunochemical identification of the novel protein kinase C ϕ (nPKC ϕ) and the atypical protein kinase C λ (aPKC λ) isoforms in retinas of different species were analyzed by immunohistochemistry and SDS-PAGE/Western blotting. nPKC ϕ immunoreactivity is associated with bipolar cells of mammalian (rabbit, rat and guinea pig) retinas but not the non-mammalian goldfish retina which has a lower concentration of nPKC ϕ. However, SDS-PAGE and Western blotting data indicate the antigen recognized by the nPKC ϕ monoclonal antibody in the retina is of a lower molecular weight than that expected for nPKC ϕ. This would suggest nPKC ϕ is more susceptible to degradation/breakdown than other PKC isoforms found in the retina or that the nPKC ϕ antibody may be recognizing an unknown retinal antigen. A comparison of nPKC ϕ and nPKC ϕ is present in the developing retina at an earlier stage than cPKC α. The typical ‘transport’ of cPKC α toward axonal terminals by phorbol-12,13-dibutyrate does not occur for nPKC ϕ yet both are translocated from the cytosolic to membrane compartments. The inner plexiform layer and the inner nuclear layer (putative horizontal cells) of all species examined (rabbit, rat, guinea pig and goldfish) exhibited positive immunoreactivity for aPKC λ as confirmed by SDS-PAGE/Western blotting. Special issue dedicated to Dr. Kinya Kuriyama.