Evaluation of the crosstalk between calcium signaling and ER stress in ulcerative colitis

• Applicant: Professor André Gessner, Ph.D., since 11/2023
• Subject Area: Anatomy and Physiology ; Gastroenterology ; Cell Biology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 467016051

Correlation between compromised intestinal barrier (integrity and activity) and the aggravation of Ulcerative colitis (UC) is well established. This is mainly due to a decrease in the activity of brush border membrane hydrolases (BBM) hydrolases and to defects in basolateral membrane proteins, instrumental for key intestinal’ functions i.e. digestion, detoxification and integrity. Defects in BBM hydrolases and in basolateral membrane proteins are found in intestinal cells of both UC patients and colitis-induced animal models. Moreover, it was found that, in freshly isolated ileum from UC patients, the majority of sucrase-isomaltase (SI), a BBM enzyme, was localized in the cytosol and not on the membrane of the cells. This data indicates that SI abnormalities are not only resulting from a decrease in its synthetic levels but probably from its folding, trafficking or sorting. The initial processing and acquisition of correct conformation of apical and basolateral proteins occur in the Endoplasmic reticulum (ER), the proper function of which is tightly linked to Ca2+ levels. Therefore, Ca2+ homeostasis maintained through the consorted activity of many Ca2+ transporter/pumps present on the plasma membrane and on the ER is instrumental for its the proper function. The intertwined contribution of inflammation, ER stress, and Ca2+ disruption to intestinal dysfunction is well recognized. Nonetheless, the initial parameters triggering the observed defects are not yet deciphered. Despite the available data on the dysfunction of BBM hydrolases and basolateral membrane proteins in UC, until now data addressing the relation between Ca2+ and ER stress in the observed dysfunction is limited. Therefore, this project aims to describe Ca2+ signalling in intestinal cells under inflammation/UC-induced conditions and to study the involvement of Ca2+ and/or ER stress in the dysfunction of BBM hydrolases as well as selected basolateral membrane proteins as encountered in UC. To achieve this aim Ca2+ signaling will be studied in Caco-2 cells cultured under normal and inflammation induced-chronic ER stress conditions. In this latter case Caco-2 cells will be cultured in the presence of either a cocktail of inflammatory cytokines or in the presence of a panel of bacterial strains. Ca2+ signalling will be also evaluated using freshly isolated intestinal cells from dextran sodium sulphate-colitis-induced animal model. Furthermore, the effect of ER stress and Ca2+ on protein folding, trafficking, and sorting of specific proteins from the BBM and from the basolateral membrane will be also investigated. The completion of this project will increase our understanding about the complexity of UC and will help in identifying new potential targets such as ER chaperones and Ca2+ modulators for new combination therapy strategies in humans.

• DFG Programme: Research Grants
• Ehemalige Antragstellerin: Privatdozentin Nahed EL-Najjar, Ph.D., until 10/2023