Marini Monica, Bruschi Maurizio, Pecci Alessandro, Romagnoli Roberta, Musante Luca, Candiano Giovanni, Ghiggeri Gian Marco, Balduini Carlo, Seri Marco, Ravazzolo Roberto
Laboratory of Molecular Genetics, G. Gaslini Institute, 16147 Genova, Italy.
Int J Mol Med. 2006 May;17(5):729-36.
Myosins of class II constitute part of a superfamily of several classes of proteins expressed in almost all eukaryotic cell types. Differences in the heavy chains produce three isoforms of class II non-muscle myosins (A, B and C), which are widely distributed in most tissues and thought to be components of the cell motor systems, although specific functional roles are largely unknown. In particular, it is still a matter of debate whether they interact and have overlapping or distinct functions. This argument is relevant not only to cell physiology, but also to human pathology since mutations of the MYH9 gene encoding non-muscle myosin heavy chain II A (NMMHC-A) cause MYH9-related disease (MYH9-RD), an autosomal dominant disorder characterized by platelet macrocytosis, thrombocytopenia and leukocyte inclusions, variably associated with sensorineural hearing loss, cataracts and/or glomerulonephritis. In this study, we report the results of yeast two-hybrid screening showing that the C-terminals of NMMHC-A and -B interact. This interaction was confirmed by immunoprecipitation in transfected COS-7 cells and in skin fibroblasts naturally expressing both isoforms. Moreover, our immunomorphological study revealed that isoforms A and B co-localize in fibroblasts, erythroblasts and kidney cells. These results suggest that isoforms A and B are strictly related molecules and support the hypothesis that their interrelationship could be involved both in the variability of clinical phenotype and selectivity of tissue damage of MYH9-RD.
II类肌球蛋白是在几乎所有真核细胞类型中表达的几类蛋白质超家族的一部分。重链的差异产生了II类非肌肉肌球蛋白的三种同工型（A、B和C），它们广泛分布于大多数组织中，被认为是细胞运动系统的组成部分，尽管其具体功能作用在很大程度上尚不清楚。特别是，它们是否相互作用以及具有重叠或不同的功能仍是一个有争议的问题。这一争论不仅与细胞生理学相关，也与人类病理学相关，因为编码非肌肉肌球蛋白重链II A（NMMHC-A）的MYH9基因突变会导致MYH9相关疾病（MYH9-RD），这是一种常染色体显性疾病，其特征为血小板大细胞症、血小板减少和白细胞包涵体，还可能伴有感音神经性听力损失、白内障和/或肾小球肾炎。在本研究中，我们报告了酵母双杂交筛选的结果，显示NMMHC-A和-B的C末端相互作用。这种相互作用在转染的COS-7细胞和天然表达这两种同工型的皮肤成纤维细胞中通过免疫沉淀得到了证实。此外，我们的免疫形态学研究表明，同工型A和B在成纤维细胞、成红细胞和肾细胞中共定位。这些结果表明，同工型A和B是密切相关的分子，并支持这样一种假说，即它们的相互关系可能与MYH9-RD临床表型的变异性和组织损伤的选择性都有关。
