Epithelial tubulogenesis is based on several intracellular events. For the initial step of the tubulogenesis, the cells have to form apicobasal polarity and this step is mediated by polarized transport. The cargo molecules have to be precisely sorted and delivered to the specific destination, such as apical and basolateral membrane domain. However, this sorting and delivering mechanism is still ambiguous. We have already identified and characterized several key transport machineries involved in apicobasal polarity formation in epithelial cells, for examples, Rab8, Syntaxin-3. Our aim is further characterization of the molecular function of these proteins.

We are going to identify the novel effector for Rab8 using GST-pull down and yeast two hybrid system. Fortunately, we were able to identify a novel interacting protein for Rab8. We are currently trying to find another interacting protein for the novel Rab8 effector protein using immunoprecipitation and pull down methods. All candidates identified in this work will be tested for the membrane traffic, cyst, and tubule formation using RNAi technique and 3D cell culture system.

As written before, the molecular mechanism of sorting and delivering of cargo molecule are poorly understood. Rab8 is known as a key protein for sorting apical cargo protein and maintaining the proper apical lumen structure. However, important questions are still remained: How Rab8 functions on apical transport and why apicobasal integrity is altered when apical transport is disrupted. To answer the question, we are going to create the molecular network map on Rab8, by finding novel interactors, including machineries and specific cargo proteins.