© 2004 American Heart Association, Inc.
Letters to the Editor |
Heat Shock–Related Protein 20 (HSP20) in Cardiomyocytes
Harrington Department of Bioengineering and Arizona, Biodesign Institute, Arizona State University, Tempe, Ariz, and, Carl T. Hayden Veteran’s Affairs Medical Center, Phoenix, Ariz, colleen.brophy@asu.edu
An extract of the first 250 words of the full text is provided, because this article has no abstract. |
To the Editor:
In the article, "Phosphoproteome analysis of cardiomyocytes subjected to ß-adrenergic stimulation," Chu et al concluded that "a de novo phosphorylation of a cardiac heat shock protein p20 was identified, for the first time, in mouse cardiomyocytes, after prolonged activation of the ß-adrenergic signaling pathway.1 However, cyclic nucleotide-dependent phosphorylation of p20, also referred to as heat shock-related protein 20 (HSP20), has been well characterized in smooth, skeletal, and cardiac muscles.2 The phosphorylation on serine 16 has also been described.3 Thus, the novelty of this report by Chu et al is limited to the animal model (mouse) and the modality of stimulation (ß-adrenergic).
Chu et al used adenoviral transfection of p20 to determine the functional relevance of the protein. They suggested that transfection of p20 leads to "increased cell contractility and intracellular calcium transients amplitudes." Our group used a different approach, that of transiently permeabililzing rat cardiomyocytes and treating the cells with phosphopeptide analogues of p20 to elucidate the function of this molecule.2 The phosphopeptide analogue, but not scrambled peptide controls, led to an increased rate of contractility because of a more rapid relaxation time. We found no change in the amplitude of the calcium transient; however, there was a more rapid rate of decay of the calcium transient. Chu et al did not indicate what the transfection efficiency was, nor did they provide any information on changes in p20 expression or phosphorylation after transfection. Without this information, it is difficult to compare and contrast the differing results.