Fig. 7

A Ca²⁺-Cn-FoxO signaling pathway regulates MuRF1 expression.

(A) HEK293T cells were transiently transfected with the MuRF1a (−638) luciferase reporter construct. Cells were incubated with FK506 or KN62 before DMSO or A23187 treatment. (B) Luciferase assay of the MuRF1a (−638) reporter cotransfected with foxo3a, wild type calcineurin (WT-Cn) or dominant-negative calcineurin (DN-Cn). (C) Diagram of the MuRF1a (−638) reporter serial deletion constructs generated for this study. The bar graph (right) shows the luciferase activity of each reporter construct relative to that of the empty expression plasmid. The red dotted box indicates the minimal cis-regulatory element of MuRF1a. The lower diagrams represent an alignment of the zebrafish, Xenopus, mouse and human MuRF1 promoters. Blue circles indicate putative FoxO binding sites (D) Whole-mount in situ hybridization detects foxo3a expression in the zebrafish heart. White arrowheads point to the heart. (E) HEK293T cells were transfected with the MuRF1a (−638) luciferase reporter and foxo3a expression plasmid. (F) HEK293T cells were transfected with the MuRF1a (−638) reporter plasmid and either a wild type or dominant negative foxo3a expression plasmid. Values on the y-axis are expressed relative to the luciferase activity of DMSO treated cells. **p<0.01; ***p<0.001; NS, not significant.