Secretory diarrhea is a major cause of morbidity and mortality in children resulting from the overstimulation of chloride (Cl-) channels in intestinal epithelial cells (IECs) that leads to overwhelming fluid secretion and life- threatening dehydration. These Cl- channels are regulated by cyclic nucleotides (cAMP and cGMP) and calcium (Ca2+) signaling pathways, but there are gaps in knowledge in how pathogens, such as rotavirus (RV), cause diarrhea through elevation of cytosolic Ca2+ ([Ca2+]c). RV persistently activates stromal interaction molecule 1 (STIM1) in infected cells, which in turn activates processes for extracellular Ca2+ entry at endoplasmic reticulum-plasma membrane (ER-PM) junctions. Activated STIM1 causes formation of ER-PM junction protein complexes that regulate Ca2+ and cAMP signaling and potentially the activation of Ca2+- activated and cAMP-activated chloride channels. Understanding the identity and activation of Cl- channels in RV infection is significant for advancing scientific knowledge of fluid secretion in the GI tract as well as future development of anti-secretory therapies to treat infectious and functional diarrhea. Thus the objective of this research is to identify the Cl- channels activated during RV infection and the regulatory role of activated STIM1 in ER-PM junctional complexes in their activation. I hypothesize that persistent activation of STIM1 stimulates the activation of Ca2+- and cAMP-dependent Cl- channels for RV-induced diarrhea. Using human intestinal enteroids (HIEs) genetically modified with biosensors as a model of IECs and a mouse model of RV diarrhea, I propose [1] to identify the Cl- channels activated during RV infection and [2] to determine the dynamic composition of ER-PM junctions with STIM1 activation in RV-infected IECs. Results from the proposed project will significantly advance our current understanding of molecular mechanisms of Cl- secretion in IECs, which can be extended to study other enteric viruses and bacterial pathogens. These findings will provide new insights into the regulatory roles of ER-PM junctions in the specialization of cell functions.
Infectious diarrheal diseases, like rotavirus, cause life-threatening dehydration and are a major cause of morbidity and mortality, especially in children. Despite the use of oral rehydration therapy and vaccines, rotavirus remains a substantial global health burden and studies of the mechanisms of fluid secretion and diarrhea in the small intestine are needed. This proposal investigates the molecular mechanisms and dysregulation of fluid secretion in rotavirus-induced diarrhea with the aim of identifying targets for development of anti-secretory treatments.
