Date of Award

2019

Degree Name

Biomedical Sciences

College

Joan C. Edwards School of Medicine

Type of Degree

Ph.D.

Document Type

Dissertation

First Advisor

Dr. Uma Sundaram, Committee Chairperson

Second Advisor

Dr. Gary Rankin

Third Advisor

Dr. Todd Green

Fourth Advisor

Dr. Richard Egleton

Fifth Advisor

Dr. Sandrine Pierre

Abstract

The integral membrane protein sodium potassium adenosine triphosphate (Na-K-ATPase), has been extensively studied in various animal cell models. Na-K-ATPase is a multifunctional enzyme which plays a significant role in cellular physiology by regulating electrochemical potential, cell volume, pH, cytosolic calcium, and many nutrient and electrolyte transport processes. As such, it has been implicated in the pathogenesis of inflammatory bowel diseases (IBD) and has been shown to play a vital role in the malabsorption of nutrients and electrolytes. In this context, a significant amount of research has been done over the last two decades to understand the mechanisms of alteration of various nutrient absorptive processes in IBD. Though it has been well acknowledged that Na-K-ATPase plays an essential role in the alteration of nutrient absorptive mechanisms during inflammation of the intestine, the molecular mechanisms responsible for the modulation of Na-K-ATPase in IBD was not known. To study the regulation of Na-K-ATPase, we used an in vitro model (rat intestinal epithelial cell line, IEC-18 cells) of intestinal epithelial cells that matured from the crypt to villus cells, very similar to that seen in the mammalian system. During the maturation process, these cells show an increase in Na-K-ATPase activity to support the absorptive capacity of the villus cells. The increased activity of Na-K-ATPase was found to be likely due to phosphorylation of the α1 subunit of Na-K-ATPase rather than altered transcription or trafficking of the enzyme. Numerous inflammatory mediators are produced during IBD; therefore, it is beneficial to uncover the role of individual inflammatory mediators in regulating transport processes regulated by Na-K-ATPase. We found that the inflammatory mediator leukotriene D4 (LTD4) stimulates the activity of Na-K-ATPase through a Ca-activated PKC pathway in crypt-like cells, while prostaglandin E2 (PGE2) reduces the activity of Na-K-ATPase through cAMP-activated PKA pathway in villus-like IEC-18 cells.

Subject(s)

Cell physiology.

Aluminum -- Toxicology.

Enzymes.

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