miR-542-5p targets c-myc and negates the cell proliferation effect of SphK1 in intestinal epithelial cells.

Intestinal epithelial barrier defects occur commonly during a variety of pathological conditions, though their underlying mechanisms are not completely understood. Sphingosine-1-phosphate (S1P) has been shown to be a critical regulator of proliferation and of maintenance of an intact intestinal epithelial barrier, as is also sphingosine kinase 1 (SphK1), the rate-limiting enzyme for S1P synthesis. SphK1 has been shown to modulate its effect on intestinal epithelial proliferation through increased levels of c-myc. We conducted genome-wide profile analysis to search for differential microRNA expression related to overexpressed SphK1 demonstrating adjusted expression of microRNA 542-5p (miR-542-5p). Here, we show that miR-542-5p is regulated by SphK1 activity and is an effector of c-myc translation that ultimately serves as a critical regulator of the intestinal epithelial barrier. miR-542-5p directly regulates c-myc translation through direct binding to the c-myc mRNA. Exogenous S1P analogs administered in vivo protect murine intestinal barrier from damage due to mesenteric ischemia reperfusion, and damaged intestinal tissue had increased levels of miR-542-5p. These results indicate that miR-542-5p plays a critical role in the regulation of S1P-mediated intestinal barrier function, and may highlight a novel role in potential therapies.