Endocytic trafficking and Wnt/ß-catenin signaling.

Several mechanisms function in the endocytic regulation of the Wnt/ß-catenin signaling pathway to promote or interrupt the progression of critical cellular processes during embryonic development or disease progression. Endocytosis was initially associated with the formation of a morphogen gradient of Wnt/ß-catenin signaling, but current studies have documented its role in defining signal intensity and propagation. Although the exact parameters that define and dictate the internalization of Wnt receptors and co-receptors via clathrin- or caveolae-mediated endocytosis remain unclear, new studies indicate that the trafficking of the signaling pool of the dual-function protein beta-catenin from sites of cell-cell contacts serve as a mechanism to finely tune the outcome of the Wnt/ß-catenin signaling. This review discusses the endocytic regulation of Wnt/ß-catenin signaling that occurs at the cell surface as well as within the cell.