Guanine nucleotide exchange factor (GEF) for RAB35 that acts as a regulator of T-cell receptor (TCR) internalization in TH2 cells. Acts by promoting the exchange of GDP to GTP, converting inactive GDP-bound RAB35 into its active GTP-bound form. Plays a role in clathrin-mediated endocytosis. Controls cytokine production in TH2 lymphocytes by controlling the rate of TCR internalization and routing to endosomes: acts by mediating clathrin-mediated endocytosis of TCR via its interaction with the adapter protein complex 2 (AP-2) and GEF activity. Dysregulation leads to impaired TCR down-modulation and recycling, affecting cytokine production in TH2 cells. Interacts with RAB35 (PubMed:26774822). Interacts with clathrin heavy chain/CLTC (By similarity). Interacts with components of the adapter protein complex 2 (AP-2) AP2A2 and AP2B1 (By similarity). Interacts with CD3E (PubMed:26774822). Expressed in a subset of dendritic cells (DCs). The FXDXF motif mediates interaction the AP-2 complex. The clathrin box motif mediates interaction with clathrin. Phosphorylated on serine and/or threonine, possibly regulating the guanine nucleotide exchange factor (GEF) activity. Mice are developmentally normal and fertile but accumulate more splenic and lymph node CD4(+) and CD8(+) effector/memory T-cells with age. TH2 cells display increased TCR-mediated responses, due to delayed surface TCR down-modulation and recycling, and increased production of cytokines. Mice have increased antigen-induced allergic responses.