Differential Turnover of Myosin Chaperone UNC-45A Isoforms Increases in Metastatic Human Breast Cancer
Differential Turnover of Myosin Chaperone UNC-45A Isoforms Increases in Metastatic Human Breast Cancer
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DOI：
10.1016/j.jmb.2011.07.012
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发表时间：
2011-09-23
影响因子：
5.6
通讯作者：
Epstein, Henry F.
中科院分区：
文献类型：
--
作者：
Guo, Wei;Chen, Daisi;Epstein, Henry F.
α-45 A是一种靶向非肌肉肌球蛋白的分子伴侣，对细胞分裂至关重要。在这里，我们发现，在人乳腺癌和乳腺癌转移来源的细胞系中，α-45 A mRNA和蛋白表达升高。此外，小发夹RNA敲低内源性过度表达的α-45 A在大多数转移性细胞系中导致细胞增殖和侵袭速率的显著降低，伴随着肌球蛋白II与肌动蛋白丝的相互作用的减少。进一步探索这些发现的机制，我们发现，在mRNA和蛋白质水平上，α-45 A作为两种异构体交替表达。这两种亚型的区别仅在于靠近氨基末端的富含脯氨酸的15个氨基酸序列。在具有转移活性的增加的表达中，同种型mRNA的比率保持恒定，但与944-氨基酸同种型相比，929-氨基酸蛋白质同种型显示出高达约3倍的增加。细胞标记实验表明，944亚型的降解速率比929亚型高5倍，这种降解需要泛素-蛋白酶体系统。爱思唯尔有限公司出版
UNC-45A is a molecular chaperone targeted to non-muscle myosins and is essential for cell division. Here, we show that UNC-45A mRNA and protein expression was elevated in human breast carcinomas and cell lines derived from breast carcinoma metastases. Moreover, small hairpin RNA knockdowns of endogenously overexpressed UNC-45A in the most metastatic cell line led to significant decreases in the rates of cell proliferation and invasion, concomitant with reduction in the interaction of myosin II with actin filaments. Exploring the mechanism of these findings further, we found that UNC-45A is alternatively expressed at the mRNA and protein levels as two isoforms. The two isoforms differ only by a proline-rich 15-amino-acid sequence near the amino-terminus. In the increased expression with metastatic activity, the ratio of the isoform mRNAs remained constant, but the 929-amino-acid protein isoform showed increases up to about 3-fold in comparison to the 944-amino-acid isoform. The differential accumulation was explained by cellular labeling experiments that showed that the 944 isoform is degraded at a 5-fold greater rate than the 929 isoform and that this degradation required the ubiquitin-proteasome system. Published by Elsevier Ltd.