RESUMEN
This study defines the in vitro phenomenon of ciliated bovine bronchial epithelial cell (BBEC) detachment from the basal epithelium and regulation of cilia motility mediated through protein kinase C epsilon (PKCepsilon). The authors determined the time course of activation and downregulation of PKCepsilon by the known PKC activator phorbol 12-myristate 13-acetate (PMA) and demonstrate that chemical inhibition of PKC by calphostin C or the novel PKC isoform inhibitor Ro 31-8220 induced striking detachment of ciliated BBECs from the basal cell monolayer within 1 hour, independent of apoptosis or necrotic cell death. The results of this study support a possible novel PKCepsilon-mediated signaling pathway through which ciliated cell attachment is maintained.
Asunto(s)
Bronquios/citología , Adhesión Celular/fisiología , Proteína Quinasa C-epsilon/antagonistas & inhibidores , Mucosa Respiratoria/citología , Mucosa Respiratoria/enzimología , Animales , Carcinógenos/farmacología , Bovinos , Adhesión Celular/efectos de los fármacos , Células Cultivadas , Cilios/efectos de los fármacos , Cilios/enzimología , Activación Enzimática/efectos de los fármacos , Activación Enzimática/fisiología , Inhibidores Enzimáticos/farmacología , Indoles/farmacología , Naftalenos/farmacología , Proteína Quinasa C-epsilon/metabolismo , Transducción de Señal/efectos de los fármacos , Transducción de Señal/fisiología , Acetato de Tetradecanoilforbol/farmacologíaRESUMEN
SGK-1 (serum- and glucocorticoid-regulated kinase-1) is a stress-induced serine/threonine kinase that is phosphorylated and activated downstream of PI3K (phosphoinositide 3-kinase). SGK-1 plays a critical role in insulin signalling, cation transport and cell survival. SGK-1 mRNA expression is transiently induced following cellular stress, and SGK-1 protein levels are tightly regulated by rapid proteasomal degradation. In the present study we report that SGK-1 forms a complex with the stress-associated E3 ligase CHIP [C-terminus of Hsc (heat-shock cognate protein) 70-interacting protein]; CHIP is required for both the ubiquitin modification and rapid proteasomal degradation of SGK-1. We also show that CHIP co-localizes with SGK-1 at or near the endoplasmic reticulum. CHIP-mediated regulation of SGK-1 steady-state levels alters SGK-1 kinase activity. These data suggest a model that integrates CHIP function with regulation of the PI3K/SGK-1 pathway in the stress response.