The role of Gα/Gα signaling in intestinal epithelial cells.

Intestinal homeostasis and the coordinated actions of digestion, absorption and excretion are tightly regulated by a number of gastrointestinal hormones. Most of them exert their actions through G-protein-coupled receptors. Recently, we showed that the absence of Gα/Gα signaling impaired the maturation of Paneth cells, induced their differentiation toward goblet cells, and affected the regeneration of the colonic mucosa in an experimental model of colitis. Although an immunohistochemical study showed that Gα/Gα were highly expressed in enterocytes, it seemed that enterocytes were not affected in Int-G/G double knock-out intestine. Thus, we used an intestinal epithelial cell line to examine the role of signaling through Gα/Gα in enterocytes and manipulated the expression level of Gα and/or Gα. The proliferation was inhibited in IEC-6 cells that overexpressed Gα/Gα and enhanced in IEC-6 cells in which Gα/Gα was downregulated. The expression of T-cell factor 1 was increased according to the overexpression of Gα/Gα. The expression of Notch1 intracellular cytoplasmic domain was decreased by the overexpression of Gα/Gα and increased by the downregulation of Gα/Gα. The relative mRNA expression of , a goblet cell marker, was elevated in a Gα/Gα knock-down experiment. Our findings suggest that Gα/Gα-mediated signaling inhibits proliferation and may support a physiological function, such as absorption or secretion, in terminally differentiated enterocytes.