Site-specific phosphorylation and point mutations of telokin modulate its Ca2+-desensitizing effect in smooth muscle.
Forskolin and 8-bromoguanosine 3'-5'-cyclic monophosphate (8-Br-cGMP) induce phosphorylation of Ser-13 of telokin and relaxation of smooth muscle at constant calcium. Comparison with the effect of wild type with aspartate (D; to mimic phosphorylation) and alanine ( A; non-phosphorylatable) mutants of telokin showed that the S13D mutant was more effective than wild type in relaxing smooth muscle at constant calcium. The efficacy of the Ser-13A, S12A, and S12D mutants was not significantly different from that of wild-type telokin. The effect of neither S13D nor Ser-13A was affected by 8-Br-cGMP, whereas the effect of wild type, S12A, and S12D was enhanced by 8-Br-cGMP, indicating the specificity of Ser-13 charge modification. Mutation of Ser-19 (a mitogen-activated protein kinase site) showed the S19A to be more effective than, and S19D to be not different from, wild-type telokin. The effect of both mutants was slightly enhanced by 8-Br-cGMP. A truncated (residues 1-142) form lacking the acidic C terminus had the same relaxant effect as wild-type telokin, whereas the C-terminal peptide (residues 142-155) had no effect. We conclude that site-specific modification of the N terminus modulates the Ca2+ -desensitizing effect of telokin on force.[1]References
- Site-specific phosphorylation and point mutations of telokin modulate its Ca2+-desensitizing effect in smooth muscle. Walker, L.A., MacDonald, J.A., Liu, X., Nakamoto, R.K., Haystead, T.A., Somlyo, A.V., Somlyo, A.P. J. Biol. Chem. (2001) [Pubmed]
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