Post-transcriptional regulation of plasminogen activator inhibitor-1 by intracellular iron in cultured human lung fibroblasts--interaction of an 81-kDa nuclear protein with the 3'-UTR.
The proteinase inhibitor, type-1 plasminogen activator inhibitor (PAI-1), is a major regulator of the plasminogen activator system involved in plasmin formation and fibrinolysis. The present study explores the effects of intracellular iron on the expression of PAI-1 and associated cell-surface plasmin activity in human lung fibroblasts; and reports the presence of a novel iron-responsive protein. ELISA revealed a dose-dependent increase in PAI-1 antigen levels expressed in the conditioned medium of cells treated with deferoxamine, in the three cell lines studied. A concomitant increase in mRNA levels was also observed by Northern analyses. Presaturation with ferric citrate quenched the effect of deferoxamine. Experiments with transcription and translation inhibitors on TIG 3-20 cells demonstrated that intracellular iron modulated PAI-1 expression at the post-transcriptional level with the requirement of de-novo protein synthesis. Electrophoretic mobility shift assay and UV crosslinking assays revealed the presence of an approximately 81-kDa nuclear protein that interacted with the 3'-UTR of PAI-1 mRNA in an iron-sensitive manner. Finally, we demonstrated that the increased PAI-1 is functional in suppressing cell-surface plasmin activity, a process that can affect wound healing and tissue remodeling.
Radha
K S
KS
Department of Physiology, Faculty of Medicine, University of Miyazaki, Miyazaki, Japan. radharao@med.miyazaki-u.ac.jp
Sugiki
M
M
Harish Kumar
M
M
Omura
S
S
Maruyama
M
M
D020413:3' Untranslated Regions; D000941:Antigens / Q000737:chemistry; D015152:Blotting, Northern; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D003432:Cross-Linking Reagents / Q000494:pharmacology; D017077:Culture Media, Conditioned / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D003676:Deferoxamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D005290:Ferric Compounds / Q000494:pharmacology; D005341:Fibrinolysin / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism; D006801:Humans; D007501:Iron / Q000378:metabolism; D008168:Lung / Q000166:cytology*; D010957:Plasmids / Q000378:metabolism; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics* / Q000378:metabolism*; D014176:Protein Biosynthesis; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D014466:Ultraviolet Rays; D014945:Wound Healing
D020413:3' Untranslated Regions; D000941:Antigens; D003432:Cross-Linking Reagents; D017077:Culture Media, Conditioned; D005290:Ferric Compounds; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; C025314:ferric citrate; D003513:Cycloheximide; D007501:Iron; D005341:Fibrinolysin; D003676:Deferoxamine