IMMUNOLOCALIZATION OF LACRIMAL GLAND PKC ISOFORMS - EFFECT OF PHORBOLESTERS AND CHOLINERGIC AGONISTS ON THEIR CELLULAR-DISTRIBUTION

In previous studies, we showed that lacrimal gland acini express three isoforms of protein kinase C (PKC): PKC alpha-delta, and -epsilon. In the present study, we report the identification of two other PKC isof orms, namely PKC mu and -iota/lambda. Using immunofluorescence techniq ues, we showed that these isoforms are differentially located. PKC alp ha and -mu showed the most prominent membrane localization, whereas PK C delta, -epsilon and -iota/lambda were mainly cytosolic. Using cell f ractionation and western blotting techniques, we showed that the phorb ol ester, phorbol 12, 13-dibutyrate (PdBu, 10(-6) M), translocated all PKC isoforms, except PKC iota/lambda, from the soluble fraction into the particulate fraction. The effect was maximum at 5 min and persiste d at 10 min. PKC epsilon was the most responsive to PdBu reaching almo st maximal translocation at a PdBu concentration as low as 10(-9) M. T he cholinergic agonist, carbachol (10(-5) and 10(-3) M), induced trans location which was transient for PKC delta, and -mu, but persisted for 10 min for PKC epsilon. Carbachol did not translocate PKC alpha and, like PdBu, did not translocate PKC iota/lambda. We concluded that lacr imal gland PKC isoforms are differentially localized and that they tra nslocate differentially in response to phorbol esters and cholinergic agonists.