Natural helix 9 mutants of PPARγ differently affect its transcriptional activity
Broekema, Marjoleine F.; Massink, Maarten P.G.; Donato, Cinzia; de Ligt, Joep; Schaarschmidt, Joerg; Borgman, Anouska; Schooneman, Marieke G.; Melchers, Diana; Gerding, Martin N.; Houtman, René; Bonvin, Alexandre M.J.J.; Majithia, Amit R.; Monajemi, Houshang; van Haaften, Gijs W.; Soeters, Maarten R.; Kalkhoven, Eric
(2019) Molecular Metabolism, volume 20, pp. 115 - 127
(Article)
Abstract
Objective: The nuclear receptor PPARγ is the master regulator of adipocyte differentiation, distribution, and function. In addition, PPARγ induces terminal differentiation of several epithelial cell lineages, including colon epithelia. Loss-of-function mutations in PPARG result in familial partial lipodystrophy subtype 3 (FPDL3), a rare condition characterized by aberrant adipose tissue distribution
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and severe metabolic complications, including diabetes. Mutations in PPARG have also been reported in sporadic colorectal cancers, but the significance of these mutations is unclear. Studying these natural PPARG mutations provides valuable insights into structure-function relationships in the PPARγ protein. We functionally characterized a novel FPLD3-associated PPARγ L451P mutation in helix 9 of the ligand binding domain (LBD). Interestingly, substitution of the adjacent amino acid K450 was previously reported in a human colon carcinoma cell line. Methods: We performed a detailed side-by-side functional comparison of these two PPARγ mutants. Results: PPARγ L451P shows multiple intermolecular defects, including impaired cofactor binding and reduced RXRα heterodimerisation and subsequent DNA binding, but not in DBD-LBD interdomain communication. The K450Q mutant displays none of these functional defects. Other colon cancer-associated PPARγ mutants displayed diverse phenotypes, ranging from complete loss of activity to wildtype activity. Conclusions: Amino acid changes in helix 9 can differently affect LBD integrity and function. In addition, FPLD3-associated PPARγ mutations consistently cause intra- and/or intermolecular defects; colon cancer-associated PPARγ mutations on the other hand may play a role in colon cancer onset and progression, but this is not due to their effects on the most well-studied functional characteristics of PPARγ.
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Keywords: Adult, Binding Sites, Cell Line, Tumor, Colorectal Neoplasms/genetics, Female, HEK293 Cells, Humans, Lipodystrophy, Familial Partial/genetics, Mutation, Missense, PPAR gamma/chemistry, Phenotype, Protein Multimerization, Case Reports, Journal Article, Research Support, Non-U.S. Gov't
ISSN: 2212-8778
Publisher: Elsevier GmbH
Note: Funding Information: We thank the index patient and her family for their participation in this study. We thank Dr. F. Payne (Wellcome Trust Sanger Institute, UK), Dr. I. Barroso (Wellcome Trust Sanger Institute, UK), and Prof. Dr. D. Savage (University of Cambridge, UK) for helpful discussions on the SNP analysis. Understanding Society: The UK Household Longitudinal Study is led by the Institute for Social and Economic Research at the University of Essex and funded by the Economic and Social Research Council. The survey was conducted by NatCen and the genome-wide scan data were analyzed and deposited by the Wellcome Trust Sanger Institute. Information on how to access the data can be found on the Understanding Society website https://www.understandingsociety.ac.uk/. Bioinformatics support was provided by the UMCU Bioinformatics Expertise Core (UBEC; www.ubec.nl). AMJJB and JS acknowledge financial support from the Horizon 2020 West-Life e-Infrastructure Virtual Research Environment project No. 675858. We also thank members of the Kalkhoven and Van Mil laboratories for helpful discussions. Funding Information: We thank the index patient and her family for their participation in this study. We thank Dr. F. Payne (Wellcome Trust Sanger Institute, UK), Dr. I. Barroso (Wellcome Trust Sanger Institute, UK), and Prof. Dr. D. Savage (University of Cambridge, UK) for helpful discussions on the SNP analysis. Understanding Society: The UK Household Longitudinal Study is led by the Institute for Social and Economic Research at the University of Essex and funded by the Economic and Social Research Council . The survey was conducted by NatCen and the genome-wide scan data were analyzed and deposited by the Wellcome Trust Sanger Institute. Information on how to access the data can be found on the Understanding Society website https://www.understandingsociety.ac.uk/ . Bioinformatics support was provided by the UMCU Bioinformatics Expertise Core (UBEC; www.ubec.nl ). AMJJB and JS acknowledge financial support from the Horizon 2020 West-Life e-Infrastructure Virtual Research Environment project No. 675858 . We also thank members of the Kalkhoven and Van Mil laboratories for helpful discussions. Publisher Copyright: © 2018 The Authors
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