title: Loss of cell surface TFII-I promotes apoptosis in prostate cancer cells stimulated with activated α₂ -macroglobulin.
abstract: Receptor-recognized forms of α₂ -macroglobulin (α₂ M) bind to cell surface-associated GRP78 and initiate pro-proliferative and anti-apoptotic signaling. Ligation of GRP78 with α₂ M also upregulates TFII-I, which binds to the GRP78 promoter and enhances GRP78 synthesis. In addition to its transcriptional functions, cytosolic TFII-I regulates agonist-induced Ca(2+) entry. In this study we show that down regulation of TFII-I gene expression by RNAi profoundly impairs its cell surface expression and anti-apoptotic signaling as measured by significant reduction of GRP78, Bcl-2, and cyclin D1 in 1-Ln and DU-145 human prostate cancer cells stimulated with α₂ M. In contrast, this treatment significantly increases levels of the pro-apoptotic proteins p53, p27, Bax, and Bak and causes DNA fragmentation. Furthermore, down regulation of TFII-I expression activates agonist-induced Ca(2+) entry. In plasma membrane lysates p-PLCγ1, TRPC3, GRP78, MTJ1, and caveolin co-immunoprecipitate with TFII-I suggesting multimeric complexes of these proteins. Consistent with this hypothesis, down regulating TFII-I, MTJ1, or GRP78 expression by RNAi greatly attenuates cell surface expression of TFII-I. In conclusion, we demonstrate that not only does cell surface GRP78 regulate apoptosis, but it also regulates Ca(2+) homeostasis by controlling cell surface localization of TFII-I.
authors.affiliation: Department of Pathology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: U K
authors.initials: UK
authors.lastname: Misra
authors.forename: Y M
authors.initials: YM
authors.lastname: Mowery
authors.forename: G
authors.initials: G
authors.lastname: Gawdi
authors.forename: S V
authors.initials: SV
authors.lastname: Pizzo
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D015153:Blotting, Western; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D005434:Flow Cytometry; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D034622:RNA Interference; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism; D019473:Transcription Factors, TFII / Q000235:genetics / Q000378:metabolism*; D000511:alpha-Macroglobulins / Q000494:pharmacology*
chemical_list: D051242:Caveolin 1; C485368:DNAJC1 protein, human; D000091342:Endoplasmic Reticulum Chaperone BiP; C104259:GTF2I protein, human; D050956:HSP40 Heat-Shock Proteins; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D050052:TRPC Cation Channels; C104603:TRPC3 cation channel; D019473:Transcription Factors, TFII; D000511:alpha-Macroglobulins