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Sam68 contributes to intestinal inflammation in experimental and human colitis

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Abstract

Sam68 is an RNA-binding protein with an adaptor role in signal transduction. Our previous work identified critical proinflammatory and apoptotic functions for Sam68, downstream of the TNF/TNFR1 and TLR2/3/4 pathways. Recent studies have shown elevated Sam68 in inflamed tissues from rheumatoid arthritis and ulcerative colitis (UC) patients, suggesting that Sam68 contributes to chronic inflammatory diseases. Here, we hypothesized that deletion of Sam68 is protective against experimental colitis in vivo, via reductions in TNF-associated inflammatory signaling. We used Sam68 knockout (KO) mice to study the role of Sam68 in experimental colitis, including its contributions to TNF-induced inflammatory gene expression in three-dimensional intestinal organoid cultures. We also studied the expression of Sam68 and inflammatory genes in colon tissues of UC patients. Sam68 KO mice treated with an acute course of DSS exhibited significantly less weight loss and histopathological inflammation compared to wild-type controls, suggesting that Sam68 contributes to experimental colitis. Bone marrow transplants showed no pathologic role for hematopoietic cell-specific Sam68, suggesting that non-hematopoietic Sam68 drives intestinal inflammation. Gene expression analyses showed that Sam68 deficiency reduced the expression of proinflammatory genes in colon tissues from DSS-treated mice, as well as TNF-treated three-dimensional colonic organoids. We also found that inflammatory genes, such as TNF, CCR2, CSF2, IL33 and CXCL10, as well as Sam68 protein, were upregulated in inflamed colon tissues of UC patients. This report identifies Sam68 as an important inflammatory driver in response to intestinal epithelial damage, suggesting that targeting Sam68 may hold promise to treat UC patients.

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All of the data underlying this article are available in the article and in its online supplementary data. Materials such as reagents will be available upon request.

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Acknowledgements

The authors thank Dr. Stephane Richard, McGill University for providing the Sam68 KO mice. We thank the Cleveland Digestive Disease Research Core Center (DDRCC) for support, particularly Drs. Fabio Cominelli, M.D., Ph.D. (Center Director and Mouse Models Core Director), Dr. Theresa Pizarro, Ph.D. (Associate Center Director and Histology/Imaging Core Director), and Dr. Claudio Fiocchi, M.D. (Associate Center Director and Biorepository Core Director). We also thank Dr. Wei Xin, M.D., Ph.D., board-certified DDRCC Pathologist, for his expert analysis of DSS-treated colon tissues.

Funding

This work was supported by supported by the National Institute of Allergy and Infectious Diseases at National Institute of Health grants R01 AI116730 and R21 AI144264, and National Cancer Institute at National Institute of Health grant R21 CA246194, to P.R. Research reported in this publication was also supported by the National Institute Of Diabetes And Digestive And Kidney Diseases at the National Institutes of Health under Award Number P30DK097948 that supported Cleveland Digestive Disease Research Core Center Pilot/Feasibility Award to P.R. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. W.A.G. was supported by the National Institute Of Diabetes And Digestive And Kidney Diseases at the National Institutes of Health grants R01 DK128143, K01 DK105138, R03 DK123579, and Crohn’s & Colitis Foundation Senior Research Award #635911. A.R.L was supported by the National Institute of Health NIH/NEI T32 pre-doctoral training grant T32EY007157.

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Authors and Affiliations

  1. Department of Pathology, School of Medicine, Case Western Reserve University and University Hospitals Cleveland Medical Center, 2103 Cornell Road, Room 6526, Wolstein Research Building, Cleveland, OH, 44106, USA

    Wendy A. Goodman, Shrikanth C. Basavarajappa, Angela R. Liu, Franklin D. Staback Rodriguez, Tailor Mathes & Parameswaran Ramakrishnan

  2. Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA

    Parameswaran Ramakrishnan

  3. The Case Comprehensive Cancer Center, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA

    Parameswaran Ramakrishnan

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  1. Wendy A. Goodman
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  2. Shrikanth C. Basavarajappa
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  3. Angela R. Liu
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  4. Franklin D. Staback Rodriguez
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Contributions

WAG performed experiments, analyzed data, and wrote the manuscript. SB performed experiments and analyzed data. ARL, FDSR and TM performed experiments. PR conceived of the study, performed experiments, analyzed data and edited the manuscript.

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Correspondence to Parameswaran Ramakrishnan.

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Conflict of interest

PR has a patent on the use of Sam68 for modulating signaling through the TNF receptor (US8598137B2). Other authors have declared that no conflict of interest exists.

Ethics approval

All mouse studies were approved under CWRU IACUC protocol 2013-0134. All human tissue samples used in this study were slated to be discarded samples that were deidentified and procured through the Cleveland Digestive Disease Research Biorepositoy Core facility with non-human subject research IRB approval from University Hospitals, IRB number NHR-16-103 and STUDY20210825.

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Goodman, W.A., Basavarajappa, S.C., Liu, A.R. et al. Sam68 contributes to intestinal inflammation in experimental and human colitis. Cell. Mol. Life Sci. 78, 7635–7648 (2021). https://doi.org/10.1007/s00018-021-03976-7

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