Evidence That Atypical Protein Kinase C-λ and Atypical Protein Kinase C-ζ Participate in Ras-mediated Reorganization of the F-actin Cytoskeleton

Abstract

Expression of transforming Ha-Ras L61 in NIH3T3 cells causes profound morphological alterations which include a disassembly of actin stress fibers. The Ras-induced dissolution of actin stress fibers is blocked by the specific PKC inhibitor GF109203X at concentrations which inhibit the activity of the atypical aPKC isotypes λ and ζ, whereas lower concentrations of the inhibitor which block conventional and novel PKC isotypes are ineffective. Coexpression of transforming Ha-Ras L61 with kinase-defective, dominant-negative (DN) mutants of aPKC-λ and aPKC-ζ, as well as antisense constructs encoding RNA-directed against isotype-specific 5′ sequences of the corresponding mRNA, abrogates the Ha-Ras–induced reorganization of the actin cytoskeleton. Expression of a kinase-defective, DN mutant of cPKC-α was unable to counteract Ras with regard to the dissolution of actin stress fibers. Transfection of cells with constructs encoding constitutively active (CA) mutants of atypical aPKC-λ and aPKC-ζ lead to a disassembly of stress fibers independent of oncogenic Ha-Ras. Coexpression of (DN) Rac-1 N17 and addition of the phosphatidylinositol 3′-kinase (PI3K) inhibitors wortmannin and LY294002 are in agreement with a tentative model suggesting that, in the signaling pathway from Ha-Ras to the cytoskeleton aPKC-λ acts upstream of PI3K and Rac-1, whereas aPKC-ζ functions downstream of PI3K and Rac-1.This model is supported by studies demonstrating that cotransfection with plasmids encoding L61Ras and either aPKC-λ or aPKC-ζ results in a stimulation of the kinase activity of both enzymes. Furthermore, the Ras-mediated activation of PKC-ζ was abrogated by coexpression of DN Rac-1 N17.

Regulation of glioblastoma cell invasion by PKCι and RhoB

“…The actin cytoskeleton is a dynamic element within cells that undergoes changes that are essential to cell motility (Lambrechts et al, 2004). PKCi depletion resulted in the formation of long actin stress fibers; similar changes in stress fibers were described by Soloff et al (2004), in PKCi knockout mouse embryonic fibroblasts) and other studies have also implicated the atypical protein kinase C family in stress fiber loss (Uberall et al, 1999;Coghlan et al, 2000).…”

Bisindolylmaleimide I Suppresses Fibroblast Growth Factor-mediated Activation of Erk MAP Kinase in Chondrocytes by Preventing Shp2 Association with the Frs2 and Gab1 Adaptor Proteins

“…The FGF-mediated activation of Erk was completely inhibited by higher Bis I concentrations that are necessary to inhibit PKC and - (Fig. 1A) (51), and the treatment with PKC / -specific pseudosubstrate abolished FGF-mediated Erk activation (Fig. 6D), both demonstrating the role of an aPKC.…”

Protein Kinase C-ζ and Protein Kinase B Regulate Distinct Steps of Insulin Endocytosis and Intracellular Sorting

“…PI3K and its downstream effectors have been implicated in the trafficking of endocytic and exocytic vesicles in yeast and mammalian cells (20,21). Atypical PKC isoforms, such as PKC and PKC , which need phosphoinositides generated by the PI3K for their catalytic functions, may regulate vesicle trafficking by modulating cytoskeletal re-organization via Rho and Rac small GTPases (22,23). Other small GTPases controlling vesicle traffic, such as Rab proteins, can be modulated by growth factors (24) and redistributed intracellularly following receptor tyrosine kinase activation (25).…”