Abstract
Using intestinal monolayers, we showed that F-actin cytoskeletal stabilization and Ca(2+) normalization contribute to epidermal growth factor (EGF)-mediated protection against oxidant injury. However, the intracellular mediator responsible for these protective effects remains unknown. Since the protein kinase C-beta1 (PKC-beta1) isoform is abundant in our naive (N) cells, we hypothesized that PKC-beta1 is essential to EGF protection. Monolayers of N Caco-2 cells were exposed to H(2)O(2) +/- EGF, PKC, or Ca(2+) modulators. Other cells were transfected to over-express PKC-beta1 or to inhibit its expression and then pretreated with low or high doses of EGF or a PKC activator, OAG (1-oleoyl-2-acetyl-sn-glycerol), before H(2)O(2). In N monolayers exposed to oxidant, pretreatment with EGF or PKC activators activated PKC-beta1, enhanced (45)Ca(2+) efflux, normalized Ca(2+), decreased monomeric G-actin, increased stable F-actin, and protected the cytoarchitecture of the actin. PKC inhibitors prevented these protective effects. Transfected cells stably over-expressing PKC-beta1 (+3.1-fold) but not N cell monolayers were protected from injury by even lower doses of EGF or OAG. EGF or OAG rapidly activated the over-expressed PKC-beta1. Antisense inhibition of PKC-beta1 expression (-90%) prevented all measures of EGF protection. Inhibitors of Ca(2+)-ATPase prevented EGF protection in N cells as well as protective synergism in transfected cells. EGF protects the assembly of the F-actin cytoskeleton in intestinal monolayers against oxidants in large part through the activation of PKC-beta1. EGF normalizes Ca(2+) by enhancing Ca(2+) efflux through PKC-beta1. We have identified novel biologic functions, protection of actin and Ca(2+) homeostasis, among the classical isoforms of PKC.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
More From: Journal of Pharmacology and Experimental Therapeutics
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.