| Summary: | Abstract In metazoans, intracellular trafficking is mediated by many conserved pathways. The main trafficking pathways involve the Adaptor Protein complexes (AP) AP-1, AP-2 and AP-3, Clathrin and Clathrin Associated Sorting Proteins (CLASPS). These proteins direct cargoes to and from the Golgi, the endosome, the lysosome and the plasma membrane. Lipoprotein receptors are one class of proteins that use these pathways and are endocytosed by AP-2 and Disabled family proteins. Disabled family proteins are ~ conserved family of monomeric adaptor proteins and consist of a single PTB domain and have a variety of motifs associated with trafficking. C. elegans has one Disabled family member, DAB-1.1 show here that .DAB-1 is a generally expressed regulator of membrane trafficking. Loss of dab-1 function, as well as an array of molecules involved membrane trafficking, perturbs cadherin-catenin function, though I have not been able to determine the precise basis of these gene'tic interactions. I show that DAB-1 is essential for the uptake of yolk protein by developing oocytes, and for the localisation of the yolk receptor RME-2. DAB1 localisation is dependent upon c1athrin and AP-2 and it co-localises with these proteins. This shows that Disabled-mediated lipoprotein receptor endocytosis is an evolutionary conserved pathway. It also is an essential component of endocytosis in the macrophage-like coelomocytes. I have identified potential DAB-1 interacting receptors, including several lipoprotein receptors, suggesting that it is involved in multiple pathways. Finally, I demonstrate that dab-1 mutations are synthetic lethal in combination with loss-of-function mutations affecting the AP-1 and AP-3 complexes, suggesting that the reduced fluid and membrane uptake exhibited by dab-1 mutants sensitises them to defects in other trafficking pathways. ,.
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