Plays a role in intracellular protein trafficking and degradation (PubMed:12149515). May regulate CFTR chloride currents and acid-induced ASIC3 currents by modulating cell surface expression of both channels (PubMed:15317815). May also regulate the intracellular trafficking of the ADR1B receptor (By similarity). May play a role in autophagy (PubMed:12372286). Together with MARCHF2 mediates the ubiquitination and lysosomal degradation of CFTR (By similarity). Overexpression results in CFTR intracellular retention and degradation in the lysosomes (By similarity). Homooligomer (PubMed:11162552). Interacts with FZD5 (PubMed:11520064). Interacts with FZD8 (PubMed:11520064). Interacts with GRID2 and BECN1 (PubMed:12372286). Interacts with CSPG5 (PubMed:12885772). Interacts with CLCN3 (PubMed:12471024). Interacts with STX6 (By similarity). Interacts with CFTR (PubMed:12471024). Interacts with ASIC3 (PubMed:15317815). Interacts with GOLGA3 (By similarity). Interacts with NLGN1 (By similarity). Interacts with RHOQ (PubMed:11162552). Interacts with MARCHF2; the interaction leads to CFTR ubiquitination and degradation (By similarity). May interact with CACNG2 (PubMed:15136571). Enriched in synaptosomal and postsynaptic densities (PSD) fractions. Expressed in cell bodies and dendrites of Purkinje cells. Localized at the trans-Golgi network (TGN) of spermatids and the medulla of round spermatides. Ubiquitously expressed (at protein level). Expressed in dorsal root glanglion (DRG), spinal cord and brain. Isoform 1 is preferentially expressed in whole brain (at protein level) and cerebellum. Expressed in spermatocytes and spermatides but not in Sertoli cells and spermatogonia. In the cerebellum, expression increases post-natally, following maturation of this tissue (at protein level). The coiled-coil region probably mediates targeting to the Golgi, oligomerization and interaction with RHOQ. May also mediates association to membranes and interactions with GOLGA3 and STX6 (By similarity). The PDZ domain mediates interaction with ADRB1 (By similarity). Mediates also interactions with FZD5, FZD8, ASIC3, GRID2, CFTR, CLCN3. Male mice are infertile with globozoospermia. Spermatozoa display a default in acrosome formation and are unable to activate oocytes.