Golenhofen Nikola, Perng Ming Der, Quinlan Roy A, Drenckhahn Detlev
Institute of Anatomy and Cell Biology, University of Würzburg, Koellikerstrasse 6, 97070, Würzburg, Germany.
Histochem Cell Biol. 2004 Nov;122(5):415-25. doi: 10.1007/s00418-004-0711-z. Epub 2004 Oct 12.
Seven members of the small heat shock protein (sHSP) family are exceptional with respect to their constitutive high abundance in muscle tissue. It has been suggested that sHSPs displaying chaperone-like properties may stabilize myofibrillar proteins during stress conditions and prevent them from loss of function. In the present study five sHSPs (alphaB-crystallin, MKBP, HSP25, HSP20, and cvHSP) were investigated with respect to similarities and differences of their expression in heart and skeletal muscle under normal and ischemic conditions. In ischemic heart and skeletal muscle these five sHSPs translocated from cytosol to the Z-/I-area of myofibrils. Myofibrillar binding of all sHSPs was very tight and resisted for the most part extraction with 1 M NaSCN or 1 M urea. MKBP and HSP20 became extracted by 1 M NaSCN to a significant extent indicating that these two sHSPs may bind partially to actin-associated proteins which were completely extracted by this treatment. Ultrastructural localization of alphaB-crystallin showed diffuse distribution of immunogold label throughout the entire I-band in skeletal muscle fibers whereas in cardiomyocytes alphaB-crystallin was preferentially located at the N-line position of the I-band. These observations indicate different myofibrillar binding sites of alphaB-crystallin in cardiomyocytes versus skeletal muscle fibers. Further differences of the properties of sHSPs could be observed regarding fiber type distribution of sHSPs. Thus sHSPs form a complex stress-response system in striated muscle tissue with some common as well as some distinct functions in different muscle types.
小热休克蛋白（sHSP）家族的七个成员在肌肉组织中具有组成性高丰度，这一点很特殊。有人提出，具有伴侣样特性的sHSP可能在应激条件下稳定肌原纤维蛋白，并防止它们丧失功能。在本研究中，研究了五种sHSP（αB-晶状体蛋白、MKBP、HSP25、HSP20和cvHSP）在正常和缺血条件下心脏和骨骼肌中表达的异同。在缺血的心脏和骨骼肌中，这五种sHSP从细胞质转移到肌原纤维的Z/I区。所有sHSP与肌原纤维的结合都非常紧密，大部分能抵抗1 M NaSCN或1 M尿素的提取。MKBP和HSP20在很大程度上能被1 M NaSCN提取，这表明这两种sHSP可能部分结合到肌动蛋白相关蛋白上，而这些蛋白在这种处理下能被完全提取。αB-晶状体蛋白的超微结构定位显示，免疫金标记在骨骼肌纤维的整个I带中呈弥漫分布，而在心肌细胞中，αB-晶状体蛋白优先位于I带的N线位置。这些观察结果表明，αB-晶状体蛋白在心肌细胞和骨骼肌纤维中的肌原纤维结合位点不同。关于sHSP的纤维类型分布，还可以观察到sHSP特性的进一步差异。因此，sHSP在横纹肌组织中形成了一个复杂的应激反应系统，在不同肌肉类型中具有一些共同和一些独特的功能。
