Figure 8.

Schematic of the role of miR-155 in mast cells. FcεRI crosslinking (XL) induces miR-155 expression in mast cells. miR-155 acts to inhibit the expression of an Akt phosphatase and a COX-2 repressor, thereby, facilitating Akt phosphorylation (activation) and COX-2 expression which normally occur following FcεRI XL. Increased Akt phosphorylation (activation) and COX-2 expression result in the production of cytokines and prostaglandins, respectively. Thus, miR-155 is a positive regulator of FcεRI-induced cytokine production and prostaglandin biosynthesis. miR-155 has no effect on degranulation or leukotriene production.