Rab11FIP1-deficient mice develop spontaneous inflammation and show increased susceptibility to colon damage.

The small GTPase, Rab11a, regulates vesicle trafficking and cell polarity in epithelial cells through interaction with Rab11 family-interacting proteins (Rab11-FIPs). We hypothesized that deficiency of Rab11-FIP1 would affect mucosal integrity in the intestine. Global Rab11FIP1 knockout (KO) mice were generated by deletion of the second exon. Pathology of intestinal tissues was analyzed by immunostaining of colonic sections and RNA-sequencing of isolated colonic epithelial cells. A low concentration of dextran sodium sulfate (DSS, 2%) was added to drinking water for 5 days, and injury score was compared between Rab11FIP1 KO, Rab11FIP2 KO, and heterozygous littermates. Rab11FIP1 KO mice showed normal fertility and body weight gain. More frequent lymphoid patches and infiltration of macrophages and neutrophils were identified in Rab11FIP1 KO mice before the development of rectal prolapse compared with control mice. The population of trefoil factor 3 (TFF3)-positive goblet cells was significantly lower, and the ratio of proliferative to nonproliferative cells was higher in Rab11FIP1 KO colons. Transcription signatures indicated that Rab11FIP1 deletion downregulated genes that mediate stress tolerance response, whereas genes mediating the response to infection were significantly upregulated, consistent with the inflammatory responses in the steady state. Lack of Rab11FIP1 also resulted in abnormal accumulation of subapical vesicles in colonocytes and the internalization of transmembrane mucin, MUC13, with Rab14. After DSS treatment, Rab11FIP1 KO mice showed greater body weight loss and more severe mucosal damage than those in heterozygous littermates. These findings suggest that Rab11FIP1 is important for cytoprotection mechanisms and for the maintenance of colonic mucosal integrity.NEW & NOTEWORTHY Although Rab11FIP1 is important in membrane trafficking in epithelial cells, the gastrointestinal phenotype of Rab11FIP1 knockout (KO) mice had never been reported. This study demonstrated that Rab11FIP1 loss induces mistrafficking of Rab14 and MUC13 and decreases in colonic goblet cells, resulting in impaired mucosal integrity.