Date of Award

8-2013

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Program

Biomedical Sciences

Track

Cell Biology and Biochemistry

Research Advisor

Anjaparavanda P. Naren, Ph.D.

Committee

Randal K. Buddington, Ph.D. Ivan C. Gerling, Ph.D. David R. Nelson, Ph.D. Kaushik Parthasarathi, Ph.D.

Keywords

CFTR Diarrhea Gastrointestinal inflammations Inflammation-associated diarrhea Macromolecular complexes Protein-protein interactions

Abstract

Macromolecular complexes of cystic fibrosis transmembrane conductance regulator (CFTR) comprise of network of proteins that can regulate cAMP-/cGMP-activated CFTR chloride channel function. We report the physical and functional coupling of CFTR with nitric oxide (NO) producing enzyme-inducible nitric oxide synthase (iNOS) at the apical plasma membrane in inflammatory bowel disease (IBD). The complex formation requires the scaffolding protein Na+ /H+ exchanger regulatory factor 2 (NHERF2). We demonstrate that iNOS is overexpressed at or near the apical plasma membrane of gut epithelial cells in IBD and, through the stimulation of the NO-cGMP pathway, generates compartmentalized cGMP underneath the plasma membrane. This action triggers the hyperactivation of CFTR chloride channels and causes secretory diarrhea phenotype in IBD. Inhibition of CFTR and iNOS activity attenuates diarrhea in dextran sodium sulfate (DSS) induced colitis. Dissolution of the macromolecular complex in Nherf2 -/- mice renders them resistant to CFTR-mediated secretory diarrhea in murine colitis models compared to Nherf2+/+. Our findings have important therapeutic implications in IBD and other forms of gastrointestinal inflammations.

DOI

10.21007/etd.cghs.2013.0018

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