title: Endoplasmic reticulum stress increases AT1R mRNA expression via TIA-1-dependent mechanism.
abstract: As the formation of ribonucleoprotein complexes is a major mechanism of angiotensin II type 1 receptor (AT1R) regulation, we sought to identify novel AT1R mRNA binding proteins. By affinity purification and mass spectroscopy, we identified TIA-1. This interaction was confirmed by colocalization of AT1R mRNA and TIA-1 by FISH and immunofluorescence microscopy. In immunoprecipitates of endogenous TIA- 1, reverse transcription-PCR amplified AT1R mRNA. TIA-1 has two binding sites within AT1R 3'-UTR. The binding site proximal to the coding region is glyceraldehyde-3-phosphate dehydrogenase (GAPDH)-dependent whereas the distal binding site is not. TIA-1 functions as a part of endoplasmic reticulum (ER) stress response leading to stress granule (SG) formation and translational silencing. We and others have shown that AT1R expression is increased by ER stress-inducing factors. In unstressed cells, TIA-1 binds to AT1R mRNA and decreases AT1R protein expression. Fluorescence microscopy shows that ER stress induced by thapsigargin leads to the transfer of TIA-1 to SGs. In FISH analysis AT1R mRNA remains in the cytoplasm and no longer colocalizes with TIA-1. Thus, release of TIA-1-mediated suppression by ER stress increases AT1R protein expression. In conclusion, AT1R mRNA is regulated by TIA-1 in a ER stress-dependent manner.
authors.affiliation: Department of Medicine, University of Helsinki, Helsinki, FIN-00014, Finland.
authors.forename: Michael
authors.initials: M
authors.lastname: Backlund
authors.affiliation: Department of Medicine, University of Helsinki, Helsinki, FIN-00014, Finland.
authors.forename: Kirsi
authors.initials: K
authors.lastname: Paukku
authors.affiliation: Department of Medicine, University of Helsinki, Helsinki, FIN-00014, Finland Helsinki University Hospital, Helsinki, FIN-00029, Finland.
authors.forename: Kimmo K
authors.initials: KK
authors.lastname: Kontula
authors.affiliation: Department of Medicine, University of Helsinki, Helsinki, FIN-00014, Finland Heart and Lung Center, Department of Cardiology, Helsinki University Central Hospital, Helsinki, FIN-00029, Finland jukka.lehtonen@hus.fi.
authors.forename: Jukka Y A
authors.initials: JY
authors.lastname: Lehtonen
mesh_terms: D020413:3' Untranslated Regions; D001665:Binding Sites; D002478:Cells, Cultured; D059865:Endoplasmic Reticulum Stress; D005786:Gene Expression Regulation; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D039102:Poly(A)-Binding Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D044140:Receptor, Angiotensin, Type 1 / Q000235:genetics*; D000074019:T-Cell Intracellular Antigen-1
chemical_list: D020413:3' Untranslated Regions; D039102:Poly(A)-Binding Proteins; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D000074019:T-Cell Intracellular Antigen-1; C071558:TIA1 protein, human; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases