Article

Nucleotide dependent differences between the α-skeletal and α-cardiac actin isoforms

University of Pécs, Faculty of Medicine, Department of Biophysics, Pécs, Szigeti Str. 12, H-7624, Hungary.
Biochemical and Biophysical Research Communications (Impact Factor: 2.28). 05/2008; 368(3):696-702. DOI: 10.1016/j.bbrc.2008.01.158
Source: PubMed

ABSTRACT The thermodynamic properties of the actin filaments prepared from cardiomyocytes were investigated with differential scanning calorimetry. This method could distinguish between the alpha-cardiac and alpha-skeletal components of the actin filaments polymerised from ADP-actin monomers by their different melting temperatures (T(m)). Similar separation was not possible with filaments polymerised from ATP-actin monomers. Further analyses revealed that the activation energy (E(act)) was greater for filaments of alpha-skeletal actin than for alpha-cardiac actin monomers when the filaments were polymerised from ADP-actin monomers. These results showed that the alpha-cardiac actin filaments were thermodynamically less stable than the filaments of alpha-skeletal actin and their difference was nucleotide dependent. Based on these results and considering previous observations it was concluded that the existence of two actin isoforms and their nucleotide dependent conformational differences are part of the tuning regulatory mechanism by which the cardiac muscle cells can maintain their biological function under pathological conditions.

0 Followers
 · 
115 Views
 · 
2 Downloads
  • [Show abstract] [Hide abstract]
    ABSTRACT: The effect of phalloidin on the thermal stability of skeletal actin filaments polymerized from ADP-binding monomers was investigated with the method of differential scanning calorimetry. Phalloidin shifted the melting temperature of the ADP-F-actin from 59.1±1.0 to 80.0±1.2°C. The stabilizing effect of phalloidin propagated cooperatively along the filament. The cooperativity factor according to the applied model was 1.07±0.11. With these measurements it was possible to demonstrate that the binding of phalloidin has lower influence on the adjacent protomers in ADP- (k=1) than in ATP-actin filaments (k=3).
    Journal of Thermal Analysis and Calorimetry 02/2009; 95(3):709-712. DOI:10.1007/s10973-008-9407-2 · 2.21 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The effect of phalloidin on filaments polymerized from ADP-actin monomers of the heart muscle was investigated with differential scanning calorimetry. Heart muscle contains alpha-skeletal and alpha-cardiac actin isoforms. In the absence of phalloidin the melting temperature was 55 degrees C for the alpha-cardiac actin isoform and 58 degrees C for the alpha-skeletal one when the filaments were generated from ADP-actin monomers. After the binding of phalloidin the melting temperature was isoform independent (85.5 degrees C). We concluded that phalloidin stabilized the actin filaments of alpha-skeletal and alpha-cardiac actin isoforms to the same extent when they were polymerized from ADP-actin monomers.
    Journal of Thermal Analysis and Calorimetry 03/2009; 95(3):721-725. DOI:10.1007/s10973-008-9404-5 · 2.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Among six actin isoforms, alpha-skeletal and alpha-cardiac actins have similar amino acid components and are highly conserved. Although skeletal muscles essentially express alpha-skeletal actins in the adult tissue, alpha-cardiac isoform actin is prominent in the embryonic muscle tissue. Switching of actin isoforms from alpha-cardiac to alpha-skeletal actin occurs during skeletal muscle differentiation. The cardiac type alpha-actin is expressed in the regeneration and patho-physiological states of the skeletal muscles as well. In the present study, we demonstrate the morphological switching of alpha-type actin isoforms from alpha-cardiac to alpha-skeletal actin in vitro using mouse ES cells for the first time. Immunofluorescent double staining with two specific antibodies revealed that alpha-cardiac actin appeared first in myoblasts. After cell fusion to form myotubes, the cardiac type actin decreased and alpha-skeletal actin conversely increased. Finally, the alpha-skeletal isoform remained as a main actin component in the fully mature skeletal muscle fibers. The exchange of isoforms is not directly linked to the sarcomere formation. As a result, ES cells provide a useful in vitro system for exploring skeletal muscle differentiation.
    Histochemie 10/2009; 132(6):669-72. DOI:10.1007/s00418-009-0650-9 · 2.93 Impact Factor
Show more

Preview

Download
2 Downloads
Available from