Elucidating the role of Myosin 5b in microvilli assembly and in the setting of inflammation - Project Summary/Abstract Inflammatory bowel disease (IBD), comprising Crohn's Disease and Ulcerative Colitis, is a chronic condition characterized by gastrointestinal inflammation. Among the IBD subtypes, Crohn’s disease is the most common, affecting 1.6 million individuals in the United States today. The prevalence of IBD is increasing worldwide, underscoring its significance as a major health issue. Despite being a significant healthcare and economic burden there is no cure for the disease currently. The complex etiology of IBD involves a combination of genetic, environmental, and immunological/microbial factors. Currently, the precise triggers of gastrointestinal inflammation in IBD remains unclear. Recent studies highlight that patients with Crohn’s disease have increased pathogenic bacteria levels and individuals with Crohn’s disease are more susceptible to bacterial infections. Other studies have shown that microvilli and the proteins responsible for linking microvilli together, the intermicrovillar adhesion complex (IMAC), are disorganized in Crohn’s disease patients. Under normal physiological conditions, the IMAC are found at the tips of microvilli where they provide physical interactions between neighboring protrusions. The IMAC increase the functional capacity of intestinal absorptive cells by promoting dense packing of microvilli and by regulating microvilli length. To reach the microvilli tips, IMAC components must be trafficked to the apical membrane and be correctly targeted to the tips of microvilli. It is well documented that the molecular motor Myosin 7b traffics and anchors IMAC proteins from the apical membrane to the tips of microvilli. Recent findings from our group have demonstrated that Myosin 5b is the molecular motor responsible for trafficking IMAC proteins to the apical membrane of enterocytes. Interestingly, preliminary data also suggests that Myosin 5b may play a role in the pathogenesis of IBD. However, there has yet to be a single study that has investigated Myosin 5b, IMAC, and Crohn’s disease. This research proposal aims to investigate how Myosin 5b regulates microvilli assembly in the intestine and investigate the degree of susceptibility of microvilli exhibiting aberrant packing and size to pathogenic bacteria that are elevated in Crohn's disease patients. We hypothesize that Crohn's disease patients have reduced Myosin 5b protein levels, leading to mislocalization of IMAC components. We further hypothesize that the lack of IMAC delivery results in disordered microvilli thereby increasing the susceptibility of the intestinal epithelium to bacterial insults. We will use both in vivo and in vitro models to explore the alterations in Myosin 5b and IMAC components that occur in Crohn’s disease (Aim 1), and how loss of Myosin 5b affects microvilli regulation, organization, and susceptibility to bacterial insults (Aim 2). By employing Myosin 5b deficient mouse models and leveraging human Crohn’s disease tissue, we aim to gain better understanding of the function of Myosin 5b in microvilli assembly and gain novel insights into the pathogenesis of Crohn’s disease.
