Key result
Smooth muscle caldesmon rapidly dissociates the profilactin complex and induces actin polymerization, potentiated by Mg2+.
Caldesmon induces the dissociation of profilactin and subsequent actin polymerization in vitro, suggesting a potential mechanism for the regulation of actin filaments in living cells.
Hypothesis-generating for caldesmon in smooth muscle actin regulation; leaves open in vivo relevance and should not change practice.
We have investigated the effect of caldesmon, a Ca2+/calmodulin-regulated actin-binding protein, on the complex between profilin and G-actin (profilactin). We found that smooth muscle caldesmon dissociates this complex rapidly and induces the polymerization of the released actin. Native profilactin (e.g. the complex isolated from calf thymus) proved more resistant to the attack of caldesmon than a heterologous complex reconstituted from calf thymus profilin and skeletal muscle actin. The mode of caldesmon-induced profilactin dissociation was similar to that described for Mg2+, and 2 mM MgCl2 potentiated the caldesmon effect. Since both caldesmon and profilin have been found enriched in ruffling membranes of animal cells, our in vitro findings may be relevant to the regulation of actin filaments in living cells.
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Gałązkiewicz et al. (1991) studied this question. Caldesmon was evaluated on Dissociation of profilactin complex and polymerization of actin. Smooth muscle caldesmon rapidly dissociates the profilactin complex and induces the polymerization of the released actin, an effect potentiated by Mg2+.
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