Deciphering the transport metabolomes of SLC26A3, SLC26A6 and SLC26A9 in the human gastrointestinal tract

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Dysregulation of Cl- and/or HCO3- transport mediated by SLC26A3, SLC26A6 and SLC26A9 anion transporters and/or their interactions partners is the underlying cause or aggravating factor in a variety of gastrointestinal (GI) disease states. The transport function of these SLC26 isoforms has been studied in heterologous expression systems, and glimpses into their physiological relevance and regulation were obtained from gastrointestinal cell lines and knockout mouse models. However, for the human GI tract very little is known about the segmental and crypt-to-villus expression patterns, the functional interplay between SLC26 and other transporters, their molecular interaction partners, and their regulatory pathways in the different intestinal segments. To recapitulate the complex transport metabolome of SLC26A3/6/9 in GI epithelial cells in the different regions of the intestinal epithelium from the crypts to the upper villus area, we will use human gastric and intestinal enteroid cultures with three- and two-dimensional growth patterns. With this new model approach we will examine the function of SLC26A3/6/9 in anion transport in near-native human gastrointestinal epithelium, study the Cl-/HCO3- coupling ratios of SLC26A3/6 together with other project groups (P3 and P4). Moreover we will address their role in intestinal function and pathophysiology beyond cellular transport: thus we will investigate their role in goblet mucus composition and secretion, in luminal pH-microclimate maintenance, and in bacterial attachment and survival, using electrophysiological, fluorometric, biochemical methods in combination with genome editing tools. We will further explore the functional and structural interaction of SLC26A3/6/9 with CFTR, and the relevance of novel interacting proteins of SLC26A3 identified by other project groups (P5) in heterologous expression systems for their role in the human intestinal epithelium.