Ligation of prostate cancer cell surface GRP78 activates a proproliferative and antiapoptotic feedback loop: a role for secreted prostate-specific antigen.
GRP78, a well characterized chaperone in the endoplasmic reticulum, is critical to the unfolded protein response. More recently, it has been identified on the cell surface, where it has many roles. On cancer cells, it functions as a signaling receptor coupled to proproliferative/antiapoptotic and promigratory mechanisms. In the current study, we demonstrate that ligation of prostate cancer cell surface GRP78 by its natural ligand, activated α(2)-macroglobulin (α(2)M*), results in a 2-3-fold up-regulation in the synthesis of prostate-specific antigen (PSA). The PSA is secreted into the medium as an active proteinase, where it binds to native α(2)M. The resultant α(2)M·PSA complexes bind to GRP78, causing a 1.5-2-fold increase in the activation of MEK1/2, ERK1/2, S6K, and Akt, which is coupled with a 2-3-fold increase in DNA and protein synthesis. PSA is a marker for the progression of prostate cancer, but its mechanistic role in the disease is unclear. The present studies suggest that PSA may be involved in a signal transduction-dependent feedback loop, whereby it promotes a more aggressive behavior by human prostate cancer cells.
Department of Pathology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Uma K
UK
Misra
Sturgis
S
Payne
Salvatore V
SV
Pizzo
D017209:Apoptosis / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology; D000091342:Endoplasmic Reticulum Chaperone BiP; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D025461:Feedback, Physiological / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008297:Male; D008744:Methylamines / Q000494:pharmacology; D017430:Prostate-Specific Antigen / Q000235:genetics / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology; D000511:alpha-Macroglobulins / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D008744:Methylamines; D000511:alpha-Macroglobulins; C027451:methylamine; D051057:Proto-Oncogene Proteins c-akt; D019893:Ribosomal Protein S6 Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; D017430:Prostate-Specific Antigen