Blebbistatin specifically inhibits actin-myosin interaction in mouse cardiac muscle

Abstract

Blebbistatin is a powerful inhibitor of actin-myosin interaction in isolated contractile proteins. To examine whether blebbistatin acts in a similar manner in the organized contractile system of striated muscle, the effects of blebbistatin on contraction of cardiac tissue from mouse were studied. The contraction of paced intact papillary muscle preparations and shortening of isolated cardiomyocytes were inhibited by blebbistatin with inhibitory constants in the micromolar range (1.3-2.8 muM). The inhibition constants are similar to those previously reported for isolated cardiac myosin subfragments showing that blebbistatin action is similar in filamentous myosin of the cardiac contractile apparatus and isolated proteins. The inhibition was not associated with alterations in action potential duration or decreased influx through L-type Ca(2+) channels. Experiments on permeabilized cardiac muscle preparations showed that the inhibition was not due to alterations in Ca(2+) sensitivity of the contractile filaments. The maximal shortening velocity was not affected by 1 muM blebbistatin. In conclusion, we show that blebbistatin is an inhibitor of the actin-myosin interaction in the organized contractile system of cardiac muscle and that its action is not due to effects on the Ca(2+) influx and activation systems.

Myofilament Ca2+ sensitization causes susceptibility to cardiac arrhythmia in mice

“…While a specific Ca 2+ desensitizing compound does not exist, the myosin ATPase inhibitor blebbistatin has been used as a contractile uncoupling agent for electrophysiological studies and has been reported to have either minimal or no significant effects on cardiac ion channels and APs (28). Given that blebbistatin inhibits force generation of strongly attached crossbridges (23) and based upon the indirect interaction between troponin C and crossbridges (29), we hypothesized that blebbistatin would also decrease myofilament Ca 2+ sensitivity.…”

Interdependency of cell adhesion, force generation and extracellular proteolysis in matrix remodeling

“…3C,D). Cytochalasin D disrupts the formation of actin filaments, whereas blebbistatin specifically inhibits non-muscular myosin II (Dou et al, 2007;Fenteany and Zhu, 2003;Schliwa, 1982). We counted and evaluated on average 90 cells for the Cytochalsin D and 130 cells for the blebbistatin treatment.…”

Blebbistatin extends culture life of adult mouse cardiac myocytes and allows efficient and stable transgene expression

“…The specificity of blebbistatin may be a basis for its superiority to BDM in our side-to-side experiments. Blebbistatin, being relatively recently characterized as a contraction inhibitor, has been less studied, and so far most published reports have evaluated it as a specific myosin II inhibitor (2,6,12). In a recent study by Dou et al (6), 10 M blebbistatin inhibited papillary muscle force and cardiomyocyte shortening but showed no effects on Ca 2ϩ currents via L-type channels and the duration of action potential.…”

“…Blebbistatin, being relatively recently characterized as a contraction inhibitor, has been less studied, and so far most published reports have evaluated it as a specific myosin II inhibitor (2,6,12). In a recent study by Dou et al (6), 10 M blebbistatin inhibited papillary muscle force and cardiomyocyte shortening but showed no effects on Ca 2ϩ currents via L-type channels and the duration of action potential. This is in contrast with the following effects observed in the presence of BDM: exposure to BDM induces a dose-dependent shortening of action potential and progressively inhibits the current through L-type Ca 2ϩ channels (4).…”