Li Yan, Friedmann David R, Mhatre Anand N, Lalwani Anil K
Laboratory of Molecular Otology, Department of Otolaryngology, New York University School of Medicine, New York, New York 10016, USA.
Cell Motil Cytoskeleton. 2008 May;65(5):393-405. doi: 10.1002/cm.20268.
MYH9 encodes a class II nonmuscle myosin heavy chain-A (NMHC-IIA), a widely expressed 1960 amino acid polypeptide, with translated molecular weight of 220 kDa. From studies of type II myosin in invertebrates and analogy with the skeletal and smooth muscle myosin II, NMHC-IIA is considered to be involved in diverse cellular functions, including cell shape, motility and division. The current study assessed the consequences of two separate, naturally occurring MYH9 dominant mutant alleles, MYH9(R702C) and MYH9(R705H) linked to syndromic and nonsyndromic hearing loss, respectively, upon diverse NMHC-IIA related functions in two separate cultured cell lines. MYH9-siRNA-induced inhibition of NMHC-IIA in HeLa cells or HEK293 cells resulted in alterations in their shape, actin cytoskeleton and adhesion properties. However, HeLa or HEK293 cells transfected with naturally occurring MYH9 mutant alleles, MYH9(R702C) or MYH9(R705H), as well as in vitro generated deletion derivatives, MYH9(DeltaN592) or MYH9(DeltaC570), were unaffected. The effects of MYH9-siRNA-induced suppression underline the critical role of NMHC-IIA in maintenance of cell shape and adhesion. However, the results also indicate that the NMHC-IIA mutants, R702C and R705H do not inactivate or suppress the endogenous wild type NMHC-IIA within the HeLa or HEK293 cell assay system.
MYH9编码一种II类非肌肉肌球蛋白重链A（NMHC-IIA），这是一种广泛表达的含有1960个氨基酸的多肽，其翻译后的分子量为220 kDa。通过对无脊椎动物中II型肌球蛋白的研究以及与骨骼肌和平滑肌肌球蛋白II的类比，NMHC-IIA被认为参与多种细胞功能，包括细胞形状、运动性和分裂。本研究评估了两个单独的、自然发生的与综合征性和非综合征性听力损失相关的MYH9显性突变等位基因MYH9(R702C)和MYH9(R705H)对两种不同培养细胞系中多种与NMHC-IIA相关功能的影响。在HeLa细胞或HEK293细胞中，MYH9-siRNA诱导的NMHC-IIA抑制导致细胞形状、肌动蛋白细胞骨架和黏附特性发生改变。然而，用自然发生的MYH9突变等位基因MYH9(R702C)或MYH9(R705H)以及体外产生的缺失衍生物MYH9(DeltaN592)或MYH9(DeltaC570)转染的HeLa或HEK293细胞未受影响。MYH9-siRNA诱导的抑制作用强调了NMHC-IIA在维持细胞形状和黏附中的关键作用。然而，结果还表明，在HeLa或HEK293细胞检测系统中，NMHC-IIA突变体R702C和R705H不会使内源性野生型NMHC-IIA失活或抑制其活性。
