AdipoR2 is transcriptionally regulated by ER stress-inducible ATF3 in HepG2 human hepatocyte cells.
Adiponectin acts as an insulin-sensitizing adipokine that protects against obesity-linked metabolic disease, which is generally associated with endoplasmic reticulum (ER) stress. The physiological effects of adiponectin on energy metabolism in the liver are mediated by its receptors. We found that the hepatic expression of adiponectin receptor 2 (AdipoR2) was lower, but the expression of markers of the ER stress pathway, 78 kDa glucose-regulated protein (GRP78) and activating transcription factor 3 (ATF3), was higher in the liver of ob/ob mice compared with control mice. To investigate the regulation of AdipoR2 by ER stress, we added thapsigargin, an ER stress inducer, to a human hepatocyte cell line, HepG2. Addition of the ER stress inducer increased the levels of GRP78 and ATF3, and decreased that of AdipoR2, whereas addition of a chemical chaperone, 4-phenyl butyric acid (PBA), could reverse them. Up- or down-regulation of ATF3 modulated the AdipoR2 protein levels and AdipoR2 promoter activities. Reporter gene assays using a series of 5'-deleted AdipoR2 promoter constructs revealed the location of the repressor element responding to ER stress and ATF3. In addition, using electrophoretic mobility shift and chromatin immunoprecipitation assays, we identified a region between nucleotides -94 and -86 of the AdipoR2 promoter that functions as a putative ATF3-binding site in vitro and in vivo. Thus, our findings suggest that the ER stress-induced decrease in both protein and RNA of AdipoR2 results from a concomitant increase in expression of ATF3, which may play a role in the development of obesity-induced insulin resistance and related ER stress in hepatocytes.
Koh
In-uk
IU
Division of Metabolic Disease, Department of Biomedical Science, National Institutes of Health, Seoul, South Korea.
Lim
Joo H
JH
Joe
Myung K
MK
Kim
Won H
WH
Jung
Myeong H
MH
Yoon
Jong B
JB
Song
Jihyun
J
D051700:Activating Transcription Factor 3 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D047369:Chromatin Immunoprecipitation; D004247:DNA / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000502:physiology*; D000091342:Endoplasmic Reticulum Chaperone BiP; D017353:Gene Deletion; D015870:Gene Expression / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D006360:Heat-Shock Proteins / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D009765:Obesity / Q000378:metabolism; D010654:Phenylbutyrates / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D054419:Receptors, Adiponectin / Q000235:genetics* / Q000378:metabolism; D050436:Regulatory Elements, Transcriptional / Q000235:genetics; D013312:Stress, Physiological / Q000187:drug effects / Q000502:physiology*; D019284:Thapsigargin / Q000494:pharmacology; D014162:Transfection
C475420:ADIPOR2 protein, human; C490449:ATF3 protein, human; D051700:Activating Transcription Factor 3; C103002:Atf3 protein, mouse; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D010654:Phenylbutyrates; D034741:RNA, Small Interfering; D054419:Receptors, Adiponectin; C475421:adiponectin receptor 2, mouse; D019284:Thapsigargin; C075773:4-phenylbutyric acid; D004247:DNA