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Biochem Biophys Res Commun. 2002 Feb 8;290(5):1368-75.

Calmodulin and cyclin D anchoring sites on the Src-suppressed C kinase substrate, SSeCKS.

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Department of Medicine and Ruttenberg Cancer Center, Mount Sinai School of Medicine, Box 1090, One Gustave L. Levy Place, New York, New York 10029-6574, USA.


SSeCKS and its human orthologue, Gravin, are large scaffolding proteins that are thought to facilitate mitogenic control by anchoring key signal mediators such as protein kinase (PK) C, PKA, the plasma membrane associated isoform of alpha-1,4-galactosyltransferase (GalTase), beta2-adrenergic receptor, and cyclins. SSeCKS is also a major PKC substrate and phosphatidylserine-dependent PKC binding protein whose phosphorylation sites shares homology with a site in the MARCKS protein that encodes phosphorylation-sensitive calmodulin (CaM) binding activity. In the present study, we mapped the in vitro binding sites for CaM and cyclins on SSeCKS. Four CaM binding sites were identified by binding assays that conform to the so-called 1-5-10 motif. Notably, CaM binding was antagonized by prephosphorylation of SSeCKS by PKC. We also identified two major cyclin binding (CY) sites that overlap a major PKC phosphorylation site in SSeCKS (Ser(507/515)), and showed that cyclin D binding is attenuated if SSeCKS is prephosphorylated by PKC. These data suggest that the scaffolding activities of SSeCKS are modulated by mitogenically stimulated kinases such as PKC.

[Indexed for MEDLINE]

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