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αB-crystallin is highly expressed in the heart and slow skeletal muscle; however, the roles of αB-crystallin in the muscle are obscure. Previously, we showed that αB-crystallin localizes at the sarcomere Z-bands, corresponding to the focal adhesions of cultured cells. In myoblast cells, αB-crystallin completely colocalizes with microtubules and maintains cell shape and adhesion. In this study, we show that in beating cardiomyocytes α-tubulin and αB-crystallin colocalize at the I- and Z-bands of the myocardium, where it may function as a molecular chaperone for tubulin/microtubules. Fluorescence recovery after photobleaching (FRAP) analysis revealed that the striated patterns of GFP-αB-crystallin fluorescence recovered quickly at 37°C. FRAP mobility assay also showed αB-crystallin to be associated with nocodazole-treated free tubulin dimers but not with taxol-treated microtubules. The interaction of αB-crystallin and free tubulin was further confirmed by immunoprecipitation and microtubule sedimentation assay in the presence of 1–100 μM calcium, which destabilizes microtubules. Förster resonance energy transfer analysis showed that αB-crystallin and tubulin were at 1–10 nm apart from each other in the presence of colchicine. These results suggested that αB-crystallin may play an essential role in microtubule dynamics by maintaining free tubulin in striated muscles, such as the soleus or cardiac muscles. [ABSTRACT FROM AUTHOR]

Resilience to stretch stress is an important characteristic that helps maintain cell adhesion and consequently, human health. This study aimed to elucidate the underlying mechanism of adaptation to stretch stress regulated by the molecular chaperone αB-crystallin. Three rat myoblast L6 cell lines, wild type (L6-WT), αB-crystallin knock down (L6-KD), and αB-crystallin overexpressing (L6-OE) cells were used. Muscle cells are less motile because they are specialized for contraction. Forced stretch stress was given to the three cell lines on a soft adhesive sheet, and we found that L6-OE cells showed the highest resilience to stretch stress and the least motility compared to other cell lines. Conversely, L6-KD cells showed the least resilience to stretch stress. Vinculin staining showed that total focal adhesion (FA) size and area of L6-OE cells were significantly larger than those of other cell types. Thus αB-crystallin in myoblast cells contributes the resilience of FA stability during stretch stress. [ABSTRACT FROM AUTHOR]