Incubation of permeabilized rat myocytes with phosphopeptide analogues of HSP20 increased the rate of shortening, lengthening, and calcium transient decay.
Does phosphorylated HSP20 increase myocyte shortening rate in rat heart models?
Phosphorylated HSP20 increases myocyte shortening rate through increases in calcium uptake and more rapid lengthening in rat heart models.
BACKGROUND: The small heat shock proteins HSP20, HSP25, alphaB-crystallin, and myotonic dystrophy kinase binding protein (MKBP) may regulate dynamic changes in the cytoskeleton. For example, the phosphorylation of HSP20 has been associated with relaxation of vascular smooth muscle. This study examined the function of HSP20 in heart muscle. METHODS AND RESULTS: Western blotting identified immunoreactive HSP20, alphaB-crystallin, and MKBP in rat heart homogenates. Subcellular fractionation demonstrated that HSP20, alphaB-crystallin, and MKBP were predominantly in cytosolic fractions. Chromatography with molecular sieving columns revealed that HSP20 and alphaB-crystallin were associated in an aggregate of approximately 200 kDa, and alphaB-crystallin coimmunoprecipitated with HSP20. Immunofluorescence microscopy demonstrated that the pattern of HSP20, alphaB-crystallin, and actin staining was predominantly in transverse bands. Treatment with sodium nitroprusside led to increases in the phosphorylation of HSP20, as determined with 2-dimensional immunoblots. Incubation of transiently permeabilized myocytes with phosphopeptide analogues of HSP20 led to an increase in the rate of shortening. The increased shortening rate was associated with an increase in the rate of lengthening and a more rapid decay of the calcium transient. CONCLUSIONS: HSP20 is associated with alphaB-crystallin, possibly at the level of the actin sarcomere. Phosphorylated HSP20 increases myocyte shortening rate through increases in calcium uptake and more rapid lengthening.
Pipkin et al. (Tue,) conducted a other in Rat heart muscle function. Phosphopeptide analogues of HSP20 / Sodium nitroprusside was evaluated on Myocyte shortening rate and calcium transient decay. Incubation of permeabilized rat myocytes with phosphopeptide analogues of HSP20 increased the rate of shortening, lengthening, and calcium transient decay.