Guanine nucleotide exchange factor (GEF) regulating clathrin-mediated endocytosis through RAB35 activation. Promotes the exchange of GDP to GTP, converting inactive GDP-bound RAB35 into its active GTP-bound form. Regulates clathrin-mediated endocytosis of synaptic vesicles and mediates exit from early endosomes (PubMed:20154091, PubMed:20937701). Binds phosphatidylinositol-phosphates (PtdInsPs), with some preference for PtdIns(3)P (By similarity).