RhoA leads to up-regulation and relocalization of utrophin in muscle fibers.

International audienceUp-regulation of utrophin, a homolog of dystrophin, is known to ameliorate the dystrophic phenotype in animal models of Duchenne muscular dystrophy. We have previously demonstrated that the active form of RhoA (RhoAV14) increases the expression of utrophin and its localization at the plasma membrane in cultured myoblasts. In this paper, we ask whether RhoAV14 can up-regulate utrophin also in mice. A plasmid encoding for RhoAV14 was injected into skeletal muscles followed by electroporation. Muscles expressing RhoAV14 were analyzed by Western-immunoblotting, real time PCR amplification and immunohistochemistry. We found that RhoAV14 increased utrophin protein expression and distribution specifically at the plasma membrane in muscle fibers without any effect on utrophin transcription. Utrophin up-regulation, uncoupled from that of its mRNA, has been previously observed in pathological processes and in normal regenerating conditions

Chemical modification of the sole histidine residue of smooth muscle caldesmon

AbstractCaldesmon was stoichiometrically N-carbethoxylated specifically at the only histidine residue (His-610) with diethylpyrocarbonate. Carbethoxylation of a 1:1 molar complex of caldesmon and calmodulin in the presence of Ca2+ resulted in the stoichiometric N-carbethoxylation of His-610 of caldesmon and His-107 of calmodulin. Carbethoxy-caldesmon, like the unmodified protein, bound to immobilized calmodulin (in the presence of Ca2+) and to immobilized tropomyosin (at low ionic strength). The affinity of F-actin for carbethoxy-caldesmon (K4 = 1.29 × 10−4M) was similar to that for unmodified caldesmon (K4 = 0.88 × 10−4M), and the modified protein was as effective as control caldesmon in the inhibition of the actin-activated MgATPase of skeletal muscle myosin. We conclude that the predicted basic amphiphilic α-helical sequence (Arg-593-His-610) does not represent the calmodulin-binding site of caldesmon. Furthermore, His-610 does not play a major role in the interaction of caldesmon with F-actin or tropomyosin

dystrophin and utrophin complexed with different associated proteins in cardiac Purkinje fibres

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