Regulation of Rotavirus Replication

Baylor College Of Medicine, Houston TX

Investigators

Linked publications, trials & patents

Abstract

PROJECT SUMMARY Our long-term goal is to understand how rotavirus (RV) exploits cellular pathways such as autophagy membranes, calcium homeostasis, and lipid metabolism including lipid droplet (LD) formation to enhance their replication and cause life-threatening diarrhea. Despite the global introduction of vaccines for RV over a decade ago, RV infections still cause >200,000 deaths annually, mostly in low-income countries, highlighting the need for a more complete understanding of RV pathogenesis. To establish an ideal environment for replication, RV reprograms the lipid metabolism of the infected cell. We recently discovered that RV infection leads to the proteasomal degradation of the triglyceride (TG) neutral lipid synthesis enzyme DGAT1 (diacylglycerol O- acyltransferase1). We found the RV nonstructural protein NSP2 is a new virulence factor that mediates DGAT1 degradation. DGAT1 degradation results in unexpected, enhanced LD formation, elevated TGs, elevated RV yields, and reduced or a complete loss of expression of intestinal digestive or absorptive enzymes, or proteins required for intestinal epithelial structure and function. Thus, NSP2-induced DGAT1 degradation is a new underlying mechanism of intestinal malabsorption and diarrhea. Another consequence of RV reprogramming of cellular lipid metabolism is the induction of cytoplasmic organelles (viroplasms) formed by two viral nonstructural proteins NSP2 and NSP5 and LDs that form a physical platform for efficient viral replication and maturation. LDs are dynamic, multi-functional intracellular organelles involved in lipid storage and metabolism as well as in signal transduction, membrane trafficking and modulation of immune and inflammatory responses. LDs play essential roles in several viral and intracellular bacterial infections and are important in many aspects of health and disease (metabolism, diabetes, obesity, heart disease). However, mechanistic information of the interplay between lipid accumulation, and the cellular sites and proteins required for LD biogenesis is far from complete. We propose to build on our exciting new findings to define basic mechanisms regulating lipid metabolism including DGAT1 degradation and LD formation in the intestine using RV as a model pathogen and human intestinal enteroids as a human intestinal model. We propose experiments to answer two questions. (1) What molecular mechanisms trigger NSP2-induced DGAT1 degradation leading to malabsorptive diarrhea? (2) What mechanisms elicit RV- mediated lipid reprogramming responsible for increased TG and LD biogenesis required for virus assembly/replication and pathogenesis? These studies are significant because viral perturbations of host signaling and metabolic pathways that involve LDs are critical for multiple pathogens. Because RVs replicate in enterocytes in the tips of the villi in the small intestine, the major site of fat absorption critical for energy production, membrane biosynthesis and brain development, our studies may explain why RV-induced gastroenteritis causes more severe, life-threatening disease compared to other enteric infections, and why children exhibit delayed growth and cognitive ability if they survive their RV-intestinal and diarrheal insult.