Abundance and Location of the Small Heat Shock Proteins HSP25 and αB-Crystallin in Rat and Human Heart

Abstract
Background In the heart, there are high constitutive levels of the two related small heat shock proteins, HSP25 and αB-crystallin. To gain insight into their functional role, we have analyzed abundance and location of both proteins in rat and human hearts at different stages of development and in diseased state. Methods and Results Immunoblotting analysis of rat ventricular tissue at fetal, neonatal, and adult stages reveals the level of HSP25 to decline strongly during development, whereas the level of αB-crystallin remains nearly constant. In parallel, the portion of phosphorylated isoforms of HSP25 decreases as shown by two-dimensional polyacrylamide gel electrophoresis. HSP25 is detected in cardiomyocytes and endothelial and vascular smooth muscle cells, whereas αB-crystallin is detected in cardiomyocytes only by immunofluorescence and immunoelectron microscopy. Both proteins colocalize in the I-band and M-line region of myofibrils in cardiomyocytes. In diseased and transplanted adult human hearts, HS...

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