Impairment of the normal function of intestinal epithelial cells (IECs) contributes to the development of intestinal diseases such as Crohn's disease (CD) and ulcerative colitis. Because our understanding of these diseases is limited, their treatment remains far from optimal. One CD-relevant cell type is the Paneth cell, which is a specialized secretory cell that creates a nurturing and anti-bacterial environment to maintain intestinal integrity. Therefore, it is important to define how the cell fate and function of Paneth cells are controlled in order to uncover the CD pathology and develop new therapeutics. Here, we investigated the mechanisms that regulate Paneth cell homeostasis in vitro, ex vivo and in vivo, with special focus on the role of the atypical Protein Kinase C lambda/iota (PKCl/i).Methods:
The expression of PKCl/i was analyzed by immunohistochemistory in mouse and human intestines from 40 CD patients. By crossing PKCl/i-floxed mice with Villin-cre or Defa6-cre line, we generated the mouse lacking PKCl/i in either IECs or Paneth cells, and analyzed their phenotype in terms of Paneth cell alteration, intestinal inflammation and tumorigenesis. 3D organoid system was also used to examine the differentiation potential for Paneth cells.Results:
The expression of PKCl/i is highly enriched in Paneth cells in both mouse and human small intestine, and it decreases with progression of CD. The selective inactivation of PKCl/i in IECs results in the loss of mature Paneth cells, accumulation of intermediate cells between Paneth and goblet cells, and increased IEC death, enteritis and tumorigenesis while Paneth cell-specific loss of PKCl/i does not induce any alteration in the intestine. Combination of in vitro, organoid and in vivo studies demonstrated that PKCl/i is required for Paneth cell differentiation at the level of Atoh1 and Gfi1, through the regulation of protein stability of a PRC2 component, EZH2, by direct phosphorylation.Conclusions:
PKCl/i plays a critical role to suppress intestinal inflammation and tumorigenesis through the control of Paneth cell fate and IEC survival. Therefore, PKCl/i could be a novel therapeutic target for CD through the restoring the Paneth cell function.