Misra U K, Wang F, Pizzo S V
Department of Pathology, Duke University Medical Center, Durham, North Carolina 27710, USA.
J Cell Biochem. 2009 Feb 15;106(3):381-9. doi: 10.1002/jcb.22016.
Receptor-recognized forms of alpha(2)-macroglobulin (alpha(2)M*) bind to cell surface-associated GRP78 and induce proliferative and survival signaling in prostate cancer cells. As part of the cellular response to alpha(2)M*, GRP78 expression is itself upregulated. In response to other stimuli, the transcription factor TFII-I upregulates GRP78 by binding to its gene promoter. We have, therefore, studied the role of TFII-I in transcriptional upregulation of GRP78 in 1-LN human prostate cancer cells stimulated with alpha(2)M*. This treatment caused a two- to threefold increase in TFII-I and GRP78 synthesis from [(35)S]-labeled precursor amino acids. Synthesis of both TFII-I and GRP78 were significantly reduced by silencing TFII-I gene expression or pretreatment of cells with genistein or actinomycin D. Confocal microscopy was employed to demonstrate relocation of TFII-I to the nucleus. In alpha(2)M*-stimulated cells, moreover, TFII-I bound to the GRP78 promoter as determined by CHIP assay. We also demonstrate binding of TFII-I to the c-fos promoter, consistent with its role in upregulating c-fos gene expression. In non-lymphoid cells, phosphorylated c-Src is an activator of TFII-I. Ligation of GRP78 on 1-LN cells with alpha(2)M* was followed by tyrosine phosphorylation of c-Src as well as TFII-I. We conclude that alpha(2)M*-induced increase in GRP78 synthesis is caused by transcriptional upregulation of TFII-I which binds to the GRP78 promoter and thus potentiates its cell survival and antipoptotic functions in 1-LN prostate cancer cells.
受体识别形式的α2-巨球蛋白(α2M*)与细胞表面相关的GRP78结合,并在前列腺癌细胞中诱导增殖和存活信号。作为细胞对α2M反应的一部分,GRP78的表达本身会上调。响应其他刺激时,转录因子TFII-I通过结合GRP78基因启动子来上调其表达。因此,我们研究了TFII-I在α2M刺激的1-LN人前列腺癌细胞中GRP78转录上调中的作用。这种处理使TFII-I和GRP78从[35S]标记的前体氨基酸合成增加了两到三倍。通过沉默TFII-I基因表达或用染料木黄酮或放线菌素D预处理细胞,可显著降低TFII-I和GRP78的合成。采用共聚焦显微镜来证明TFII-I向细胞核的重新定位。此外,通过CHIP分析确定,在α2M刺激的细胞中,TFII-I与GRP78启动子结合。我们还证明了TFII-I与c-fos启动子的结合,这与其上调c-fos基因表达的作用一致。在非淋巴细胞中,磷酸化的c-Src是TFII-I的激活剂。用α2M连接1-LN细胞上的GRP78后,c-Src以及TFII-I发生酪氨酸磷酸化。我们得出结论,α2M*诱导的GRP78合成增加是由TFII-I的转录上调引起的,TFII-I与GRP78启动子结合,从而增强其在1-LN前列腺癌细胞中的细胞存活和抗凋亡功能。