title: Control of protein kinase C activity, phorbol ester-induced cytoskeletal remodeling, and cell survival signals by the scaffolding protein SSeCKS/GRAVIN/AKAP12.
abstract: The product of the SSeCKS/GRAVIN/AKAP12 gene ("SSeCKS") is a major protein kinase (PK) C substrate that exhibits tumor- and metastasis-suppressing activity likely through its ability to scaffold multiple signaling mediators such as PKC, PKA, cyclins, calmodulin, and Src. Although SSeCKS and PKCα bind phosphatidylserine, we demonstrate that phosphatidylserine-independent binding of PKC by SSeCKS is facilitated by two homologous SSeCKS motifs, EG(I/V)(T/S)XWXSFK(K/R)(M/L)VTP(K/R)K(K/R)X(K/R)XXXEXXXE(E/D) (amino acids 592-620 and 741-769). SSeCKS binding to PKCα decreased kinase activity and was dependent on the two PKC-binding motifs. SSeCKS scaffolding of PKC was increased in confluent cell cultures, correlating with significantly increased SSeCKS protein levels and decreased PKCα activity, suggesting a role for SSeCKS in suppressing PKC activation during contact inhibition. SSeCKS-null mouse embryo fibroblasts displayed increased relative basal and phorbol ester (phorbol 12-myristate 13-acetate)-induced PKC activity but were defective in phorbol 12-myristate 13-acetate-induced actin cytoskeletal reorganization and cell shape change; these responses could be rescued by the forced expression of full-length SSeCKS but not by an SSeCKS variant deleted of its PKC-binding domains. Finally, the PKC binding sites in SSeCKS were required to restore cell rounding and/or decreased apoptosis in phorbol ester-treated LNCaP, LNCaP-C4-2, and MAT-LyLu prostate cancer cells. Thus, PKC-mediated remodeling of the actin cytoskeleton is likely regulated by the ability of SSeCKS to control PKC signaling and activity through a direct scaffolding function.
authors: Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York 14263.
authors: Li-Wu
authors: LW
authors: Guo
authors: Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York 14263.
authors: Lingqiu
authors: L
authors: Gao
authors: Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York 14263.
authors: Julian
authors: J
authors: Rothschild
authors: Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York 14263.
authors: Bing
authors: B
authors: Su
authors: Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York 14263. Electronic address: irwin.gelman@roswellpark.org.
authors: Irwin H
authors: IH
authors: Gelman
mesh_terms: D054758:A Kinase Anchor Proteins / Q000737:chemistry / Q000502:physiology*; D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000502:physiology*; D002470:Cell Survival; D003599:Cytoskeleton / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D010703:Phorbol Esters / Q000494:pharmacology*; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000737:chemistry*
chemical_list: D054758:A Kinase Anchor Proteins; C491162:AKAP12 protein, human; C491161:Akap12 protein, mouse; D018797:Cell Cycle Proteins; D010703:Phorbol Esters; D020033:Protein Isoforms; D011493:Protein Kinase C