Photoinduced inactivation of protein kinase C by dequalinium identifies the RACK-1-binding domain as a recognition site.

Abstract

1,1'-Decamethylenebis-4-aminoquinaldinium diiodide (DECA; dequalinium) is an anti-tumor agent and protein kinase C (PKC) inhibitor whose mechanism of action with PKC is unknown. This study reports that with human PKC alpha, DECA exhibited competitive inhibition (Ki = 11.5 +/- 5 microM) with respect to RACK-1 (receptor for activated C kinase-1), an adaptor protein that has been proposed to bind activated PKC following translocation (Ron, D., Luo, J., and Mochly-Rosen, D. (1995) J. Biol. Chem. 270, 24180-24187). When exposed to UV light, DECA covalently modified and irreversibly inhibited PKC (alpha or beta), with IC50 = 7-18 microM. UV/DECA treatment of synthetic peptides modeled after the RACK-1-binding site in the C2 region of PKC beta induced modification of Ser218-Leu-Asn-Pro-Glu-Trp-Asn-Glu-Thr226, but not of a control peptide. This modification occurred at a tryptophan residue (Trp223) that is conserved in all conventional PKC isoforms. In overlay assays with native RACK-1 that had been immobilized on nitrocellulose, UV-treated control PKC alpha bound well to RACK-1, whereas UV/DECA-inactivated PKC alpha had reduced binding activity. The significance of these findings is shown with adenocarcinoma cells, which, when pretreated with 10 microM DECA and UV light, exhibited diminished 12-O-tetradecanoylphorbol-13-acetate-induced PKC alpha translocation. Overall, this work identifies DECA as a tool that prevents PKC translocation by inhibiting formation of the PKC.RACK-1 complex.

• Authors: S A Rotenberg, X G Sun
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 273 Issue 4 Pg. 2390-5 (Jan 23 1998) ISSN: 0021-9258 [Print] United States
• PMID: 9442087 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Anti-Infective Agents, Local
• Isoenzymes
• Receptors for Activated C Kinase
• Receptors, Cell Surface
• Dequalinium
• PRKCA protein, human
• Protein Kinase C
• Protein Kinase C-alpha
• Proton-Translocating ATPases
• Tetradecanoylphorbol Acetate

Topics

• Amino Acid Sequence
• Anti-Infective Agents, Local (metabolism, pharmacology)
• Binding Sites
• Dequalinium (metabolism, pharmacology)
• Humans
• Isoenzymes (antagonists & inhibitors, metabolism)
• Molecular Sequence Data
• Photochemistry
• Protein Kinase C (antagonists & inhibitors, metabolism)
• Protein Kinase C-alpha
• Proton-Translocating ATPases (metabolism)
• Receptors for Activated C Kinase
• Receptors, Cell Surface (metabolism)
• Tetradecanoylphorbol Acetate (pharmacology)
• Tumor Cells, Cultured
• Ultraviolet Rays