Dominant-negative PKC-ε impairs apical actin remodeling in parallel with inhibition of carbachol-stimulated secretion in rabbit lacrimal acini

Abstract

We investigated the involvement of PKC-epsilon in apical actin remodeling in carbachol-stimulated exocytosis in reconstituted rabbit lacrimal acinar cells. Lacrimal acinar PKC-epsilon cosedimented with actin filaments in an actin filament binding assay. Stimulation of acini with carbachol (100 microM, 2-15 min) significantly (P < or = 0.05) increased PKC-epsilon recovery with actin filaments in two distinct biochemical assays, and confocal fluorescence microscopy showed a significant increase in PKC-epsilon association with apical actin in stimulated acini as evidenced by quantitative colocalization analysis. Overexpression of dominant-negative (DN) PKC-epsilon in lacrimal acini with replication-defective adenovirus (Ad) resulted in profound alterations in apical and basolateral actin filaments while significantly inhibiting carbachol-stimulated secretion of bulk protein and beta-hexosaminidase. The chemical inhibitor GF-109203X (10 microM, 3 h), which inhibits PKC-alpha, -beta, -delta, and -epsilon, also elicited more potent inhibition of carbachol-stimulated secretion relative to Gö-6976 (10 microM, 3 h), which inhibits only PKC-alpha and -beta. Transduction of lacrimal acini with Ad encoding syncollin-green fluorescent protein (GFP) resulted in labeling of secretory vesicles that were discharged in response to carbachol stimulation, whereas cotransduction of acini with Ad-DN-PKC-epsilon significantly inhibited carbachol-stimulated release of syncollin-GFP. Carbachol also increased the recovery of secretory component in culture medium, whereas Ad-DN-PKC-epsilon transduction suppressed its carbachol-stimulated release. We propose that DN-PKC-epsilon alters lacrimal acinar apical actin remodeling, leading to inhibition of stimulated exocytosis and transcytosis.