the creation of tissue polarity during development. Rab11FIP5 has been shown to be involved in the vesicle trafficking and degradation of proteins used to coordinate embryonic development. This is conducted in a manner that helps maintain the ectoderm polarity in embryonic Drosophila. Rab11FIP5 is also suggested to be involved in aiding salivary epithelial cells to adjust to extracellular pH. V-ATPase, a proton pump protein, has been shown to be reliant on Rab11FIP5 mediated vesicle trafficking. When Rab11FIP5 is knocked down, salivary cells cannot correctly translocate V-ATPase to the plasma membrane in response to extracellular acidosis. While this pathway remains largely unknown, these results suggest a link between Rab11FIP5 function and the maintenance of the buffering capacity of saliva. Rab11FIP5 is also required for regulated exocytosis in neuroendocrine cells. Knockdown of Rab11FIP5 inhibited calcium-stimulated dense core vesicle (DCV) exocytosis in a neuroendocrine cell line BON cells. DCV membrane proteins are lost to the plasma membrane during exocytosis and recycle to the Golgi through the retrograde trafficking pathway. The requirement of Rab11FIP5 for regulated DCV exocytosis may be attributed to its role in endosome-mediated retrograde trafficking. References Further reading