| First Author | Burkart EM | Year | 2003 |
| Journal | J Biol Chem | Volume | 278 |
| Issue | 13 | Pages | 11265-72 |
| PubMed ID | 12551921 | Mgi Jnum | J:82583 |
| Mgi Id | MGI:2653723 | Doi | 10.1074/jbc.M210712200 |
| Citation | Burkart EM, et al. (2003) Phosphorylation or glutamic acid substitution at protein kinase C sites on cardiac troponin I differentially depress myofilament tension and shortening velocity. J Biol Chem 278(13):11265-72 |
| abstractText | There is evidence that multi-site phosphorylation of cardiac troponin I (cTnI) by protein kinase C is important in both long- and short-term regulation of cardiac function. To determine the specific functional effects of these phosphorylation sites (Ser-43, Ser-45, and Thr-144), we measured tension and sliding speed of thin filaments in reconstituted preparations in which endogenous cTnI was replaced with cTnI phosphorylated by protein kinase C-epsilon or mutated to cTnI-S43E/S45E/T144E, cTnI-S43E/S45E, or cTnI-T144E. We used detergent-skinned mouse cardiac fiber bundles to measure changes in Ca(2+)-dependence of force. Compared with controls, fibers reconstituted with phosphorylated cTnI, cTnI-S43E/S45E/T144E, or cTnI-S43E/S45E were desensitized to Ca(2+), and maximum tension was as much as 27% lower, whereas fibers reconstituted with cTnI-T144E showed no change. In the in vitro motility assay actin filaments regulated by troponin complexes containing phosphorylated cTnI or cTnI-S43E/S45E/T144E showed both a decrease in Ca(2+) sensitivity and maximum sliding speed compared with controls, whereas filaments regulated by cTnI-S43E/S45E showed only decreased maximum sliding speed and filaments regulated by cTnI-T144E demonstrated only desensitization to Ca(2+). Our results demonstrate novel site specificity of effects of PKC phosphorylation on cTnI function and emphasize the complexity of modulation of the actin-myosin interaction by specific changes in the thin filament. |
