Transcriptional regulation of LDL receptor-related protein by IFN-gamma and the antagonistic activity of TGF-beta(1) in the RAW 264.7 macrophage-like cell line.
Low density lipoprotein receptor-related protein (LRP) is a major receptor for multiple ligands, including chylomicron and VLDL remnants, bacterial toxins, viruses, proteinases, lipoprotein lipase, and activated alpha2-macroglobulin (alpha2M). In this study, we used Northern blot analyses and nuclear run-on experiments to demonstrate that interferon-gamma (IFN-gamma) causes a concentration-dependent decrease in steady-state LRP mRNA expression and gene transcription rate in RAW 264.7 cells. IFN-gamma also markedly increased expression of inducible nitric oxide synthase (NOS), as expected; however, the increase in nitric oxide was not responsible for the down-regulation of LRP expression since the NOS inhibitor, N(G)-monomethyl-L-arginine, did not preserve LRP expression in IFN-gamma-treated cells. Transforming growth factor-beta1 (TGF-beta1; 2.5 ng/mL) had no independent effect on LRP expression and did not modify the response to IFN-gamma when the two cytokines were added simultaneously to cultures. When TGF-beta1 was added 24 h prior to IFN-gamma, the extent of LRP down-regulation was significantly reduced. Specific binding of the LRP ligand, activated (125)I-alpha2M, was decreased by 76 +/- 5% in cells treated with 100 U/mL IFN-gamma, but only by 45 +/- 7% in cells treated with 100 U/mL IFN-gamma after TGF-beta1-pretreatment. The antagonistic activity of TGF-beta1 on the IFN-gamma response in RAW 264.7 cells did not result from a change in LRP mRNA stability or IFN-gamma receptor expression, as determined by Northern blot analyses and (125)I-IFN-gamma binding experiments. The studies presented here suggest that the balance between IFN-gamma and TGF-beta1 may be critical in determining LRP expression at sites of infection and inflammation.
Hussaini
I M
IM
Department of Pathology, University of Virginia Health Sciences Center, Charlottesville, 22908, USA.
LaMarre
J
J
Lysiak
J J
JJ
Karns
L R
LR
VandenBerg
S R
SR
Gonias
S L
SL
D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D002460:Cell Line; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D012333:RNA, Messenger / Q000032:analysis; D011971:Receptors, Immunologic / Q000187:drug effects / Q000235:genetics*; D017471:Receptors, Interferon / Q000032:analysis; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D019323:omega-N-Methylarginine; D000096743:Interferon gamma Receptor
D015703:Antigens, CD; D001120:Arginine; D007371:Interferon-gamma; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D012333:RNA, Messenger; D011971:Receptors, Immunologic; D017471:Receptors, Interferon; D016212:Transforming Growth Factor beta; D019323:omega-N-Methylarginine; D000096743:Interferon gamma Receptor