Molecular Programs Governing Enterococcal Translocation

Molecular Programs Governing Enterococcal Translocation Enterococcus faecalis is a commensal microbe residing in the gastrointestinal tract of healthy individuals. However, in hosts with dysbiosis or altered gut homeostasis, these bacteria can overgrow, breach intestinal barriers, and cause life-threatening systemic infections. This process, known as translocation, remains a largely unexplored phenomenon. Our team uncovered that E. faecalis produces a polysaccharide-rich extracellular matrix (ECM) that enables its movement across intestinal epithelial cell barriers. However, the mechanisms by which host cells perceive and respond to stress signals generated by these translocating enterococci remain elusive. Additionally, whether E. faecalis exploits specific molecular pathways in epithelial cells to facilitate its translocation remains unknown. Our project aims at addressing these fundamental gaps in knowledge. We postulate that E. faecalis induces endoplasmic reticulum (ER) stress in epithelial cells and that activation of the unfolded protein response (UPR) through this process promotes enterococcal egress from the intestine. Our study is innovative and significant because it has the potential to uncover key molecular mechanisms mediating E. faecalis transition from commensal to pathogen. Aim 1 will define how E. faecalis disrupts ER proteostasis in epithelial cells. Aim 2 will establish that E. faecalis-induced ER stress responses compromise intestinal barrier function. Aim 3 will test the hypothesis that disabling ER stress sensors in vivo thwarts enterococcal translocation in hosts experiencing antibiotic-induced dysbiosis. The proposed research will be accomplished by integrating our multidisciplinary expertise in E. faecalis pathogenesis, ER stress biology, and intestinal physiology. We have developed advanced models of translocation, crucial transgenic mice, sensitive ER stress reporter systems, and a unique understanding of the interplay between enterococci and the host UPR. The proposed studies could pave the way for new treatments that more effectively prevent or control systemic infections caused by gut-resident enterococci. Our project should also provide a strong rationale to define if other commensal bacteria exploit the UPR to cross intestinal barriers, hence expanding our mechanistic understanding of host-microbe interactions in the gut.