PAPA-1 Is a nuclear binding partner of IGFBP-2 and modulates its growth-promoting actions.
IGF-binding proteins (IGFBPs) have multiple cellular effects, which occur by both IGF-dependent and -independent mechanisms. IGFBP-2 is involved in the regulation of both normal and carcinogenic cell growth. To further understand the actions of IGFBP-2, we carried out a yeast two-hybrid screen to search for intracellular partner proteins using a human prostate cDNA library. We isolated Pim-1-associated protein-1 (PAP-1)-associated protein-1 (PAPA-1) as an IGFBP-2-binding protein, whose expression and subcellular localization is regulated by both IGFBP-2 and androgens. Coimmunoprecipitation and glutathione S-transferase pull-down assay confirmed the interaction in vitro, and confocal microscopy showed the colocalization of IGFBP-2 and PAPA-1 in the nucleus. Suppression of PAPA-1 by small interfering RNA treatment enhanced the growth-promoting effect of IGFBP-2. Conversely, IGFBP-2-promoted bromodeoxyuridine incorporation into LNCaP cells was abrogated by the simultaneous overexpression of myc-hPAPA-1. Mouse embryonic fibroblasts from IGFBP-2 knockout mouse showed diminished growth activity compared with wild type, and expression of FLAG-mPAPA-1 decreased cell proliferation in IGFBP-2 knockout, but not control mouse embryonic fibroblasts. These studies suggest that the growth-promoting role of IGFBP-2 in prostate cancer is inhibited by its intracellular interaction with PAPA-1.
Miyako
Kenichi
K
David Geffen School of Medicine at University of California, Los Angeles, California 90095-1752, USA.
Cobb
Laura J
LJ
Francis
Malik
M
Huang
Alden
A
Peng
Bonnie
B
Pintar
John E
JE
Ariga
Hiroyoshi
H
Cohen
Pinchas
P
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D006801:Humans; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D000073718:Pancreatitis-Associated Proteins; D011467:Prostate / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000378:metabolism; D051573:Proto-Oncogene Proteins c-pim-1 / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C494434:INO80B protein, human; D018971:Insulin-Like Growth Factor Binding Protein 2; D009687:Nuclear Proteins; C494435:PAPA-1 protein, mouse; D000073718:Pancreatitis-Associated Proteins; C000612141:REG3A protein, human; D034741:RNA, Small Interfering; D051573:Proto-Oncogene Proteins c-pim-1