Lineage-Specific Expression of Bestrophin-2 and Bestrophin-4 in Human Intestinal Epithelial Cells

Abstract

Intestinal epithelial cells (IECs) regulate the absorption and secretion of anions, such as HCO3- or Cl-. Bestrophin genes represent a newly identified group of calcium-activated Cl- channels (CaCCs). Studies have suggested that, among the four human bestrophin-family genes, bestrophin-2 (BEST2) and bestrophin-4 (BEST4) might be expressed within the intestinal tissue. Consistently, a study showed that BEST2 is expressed by human colonic goblet cells. However, their precise expression pattern along the gastrointestinal tract, or the lineage specificity of the cells expressing these genes, remains largely unknown. Here, we show that BEST2 and BEST4 are expressed in vivo, each in a distinct, lineage-specific manner, in human IECs. While BEST2 was expressed exclusively in colonic goblet cells, BEST4 was expressed in the absorptive cells of both the small intestine and the colon. In addition, we found that BEST2 expression is significantly down-regulated in the active lesions of ulcerative colitis, where goblet cells were depleted, suggesting that BEST2 expression is restricted to goblet cells under both normal and pathologic conditions. Consistently, the induction of goblet cell differentiation by a Notch inhibitor, LY411575, significantly up-regulated the expression of not BEST4 but BEST2 in MUC2-positive HT-29 cells. Conversely, the induction of absorptive cell differentiation up-regulated the expression of BEST4 in villin-positive Caco-2 cells. In addition, we found that the up- or down-regulation of Notch activity leads to the preferential expression of either BEST4 or BEST2, respectively, in LS174T cells. These results collectively confirmed that BEST2 and BEST4 could be added to the lineage-specific genes of humans IECs due to their abilities to clearly identify goblet cells of colonic origin and a distinct subset of absorptive cells, respectively.

Role of epithelial cells in the pathogenesis and treatment of inflammatory bowel disease

“…Mice lacking BEST2 develops spontaneous colitis, and are more susceptible to DSS challenge, suggesting that this channel may play a distinct role to maintain goblet cell-dependent barrier functions [46]. We have further identified that BEST2 expression is down-regulated in the inflamed colonic mucosa of UC patients [47]. Accordingly, BEST2 gene is located at the formerly identified disease susceptibility locus [48].…”

“…Besides mucin production, goblet cells secretes cytokines such as IL-7 [44] and thus may exert immunoregulatory functions, and can also deliver luminal antigens to the underlying DCs [45]. Recent studies have shown that a newly identified Clchannel, bestrophin2 (BEST2), is expressed specifically by colonic goblet cells [46,47]. Mice lacking BEST2 develops spontaneous colitis, and are more susceptible to DSS challenge, suggesting that this channel may play a distinct role to maintain goblet cell-dependent barrier functions [46].…”

PGE2 is a direct and robust mediator of anion/fluid secretion by human intestinal epithelial cells

“…Thus our results suggest that cooperation of these transporters is induced specifically in crypt IECs upon local secretion of PGE 2 . The possible involvement of other channels, such as ClC-2 or CaCCs48 remains to be elucidated. However, the existence and the role of CaCCs in the intestinal epithelia still remains controversial49, and these channels may have a more dominant role in intestinal motility50.…”

Bestrophin 1 and retinal disease

“…Other than being reportedly expressed in absorptive cells in human colon and small intestine (Ito et al, 2013), very little is known about the Bestrophin 4 protein. Bestrophin 3 shows a very broad tissue distribution and emerging evidence suggests that this anion channels plays important cell protective roles (Svenningsen, 2015) against endoplasmic reticulum stress (Lee et al, 2012), oxidative stress (Jiang et al, 2013), and inflammation (Song et al, 2014).…”