Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.1.52 (PNGase F)
 1,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Platelet-derived growth factor (PDGF) is believed to be a critical mediator of vascular smooth muscle cell (SMC) proliferation. Because insulin-like growth factor (IGF) I (IGF-I) functions as a progression factor for the mitogenic effects of PDGF, we hypothesized that IGF-I gene expression and the production of IGF binding proteins (IGFBPs) by cultured rat aortic SMCs might be regulated by one or more of the three isoforms of PDGF: PDGF-AA, -BB, and -AB. IGF-I gene expression was highly dependent on cell density: IGF-I mRNA transcripts decreased markedly as a function of cell confluence. IGF-I mRNA content was inhibited to a similar degree by PDGF-AA, -BB, and -AB through a mechanism requiring protein synthesis. The inhibition was readily apparent at 4 hours, reaching approximately 25% of control levels after 24 hours. Radioimmunoassayable IGF-I was only barely detectable in SMC-conditioned serum-free medium and not significantly modulated by PDGF. Western ligand blot revealed that vascular SMCs release 30-kd and 24-kd IGFBP into serum-free conditioned medium. PDGF isoforms did not significantly alter release of the 30-kd IGFBP but evoked a fivefold to sixfold increase in the 24-kd IGFBP. The 24-kd IGFBP was found to comigrate with IGFBP-4, a recently identified binding protein that inhibits IGF action. The 30-kd protein was not merely a glycosylated form of IGFBP-4, because it was not sensitive to N-glycanase digestion. PDGF-AA, -BB, and -AB markedly induced expression of IGFBP-4 mRNA in a time- and concentration-dependent fashion. Vascular SMCs also express IGFBP-2 mRNA, but its abundance was not induced by PDGF. In conclusion, PDGF evokes a complex pattern of regulation of genes in the IGF/IGFBP system. By inhibiting IGF-I production and specifically inducing biosynthesis of the inhibitory binding protein IGFBP-4, PDGF may set in motion mechanisms to limit the final magnitude of the mitogenic response.
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PMID:Platelet-derived growth factor isoforms decrease insulin-like growth factor I gene expression in rat vascular smooth muscle cells and selectively stimulate the biosynthesis of insulin-like growth factor binding protein 4. 137 93

Breast tumor cell lines have been shown to secrete several distinct polypeptide growth factors, although conflicting results exist for the insulin-like growth factors (IGFs). In contrast a limited number of breast tumor cell lines have definitely been shown to secrete the high affinity IGF binding proteins (IGFBPs) that modify IGF actions. To characterize the types of IGFBPs that are secreted by breast tumor cell lines, conditioned medium was collected from seven separate tumor cell lines, three of which were estrogen receptor (ER) negative, and four of which were ER positive. All three of the ER negative cell lines, MDA-231, MDA-330, and HS578T, secreted binding proteins of 49,000 and 43,000 Mr (IGFBP-3) as well as 29,000 (IGFBP-1) and 24,000 Mr. In contrast, all four ER positive cell lines secreted 34,000 (IGFBP-2) or 24,000 Mr forms, and none secreted the 49,000 and 43,000 or 29,000 Mr forms. BT-20, a cell line that is positive for ER messenger RNA (mRNA) but negative for ER protein, secreted predominantly a 34,000 Mr protein. The amount of total IGFBP activity released in 24 h ranged between 0.4 and 5.6 nM equivalents of IGFBP-1, and there was no significant difference between the ER positive and negative cell lines. The MCF-7 cells that produced predominantly 34,000 and 24,000 Mr forms showed a 1.8-fold increase in IGFBP secretion after estrogen stimulation. Immunoblotting and a specific RIA for IGFBP-1 showed that only the ER negative lines MDA-330, MDA-231, and HS578T secreted this form. Northern blotting analysis for the mRNA encoding this protein showed that both MDA-330 and MDA-231 contained a single 1.6 kilobase mRNA species that hybridized with an IGFBP-1 complementary DNA (cDNA) probe. Immunoblotting analysis of the other cell lines showed that only the 34,000 Mr form secreted by the ER positive cell lines reacted with IGFBP-2 antisera. Exposure of the conditioned media from the three ER negative cell lines to N-glycanase revealed that the 49,000 and 43,000 Mr forms of IGFBP were glycosylated and therefore probably represent IGFBP-3. We conclude that ER negative cell lines secrete three forms of IGFBPs, IGFBP-1, IGFBP-3, and a 24,000 Mr form. In contrast, the ER positive cell lines secrete predominantly IGFBP-2 and the 24,000 Mr form but do not secrete IGFBP-3 or 1.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Insulin-like growth factor binding protein secretion by breast carcinoma cell lines: correlation with estrogen receptor status. 170 Nov 24