Shelters ceramides and diacylglycerol lipids inside its START domain and mediates the intracellular trafficking of ceramides and diacylglycerol lipids in a non-vesicular manner (By similarity). Isoform 1 plays a role in neural development and skeletal muscle development. Negatively regulates apoptosis during development. N-hexadecanoylsphing-4-enine(in) = N-hexadecanoylsphing-4-enine(out) Interacts with VAPA and VAPB. Interaction with VAPB is less efficient than with VAPA. Interacts (via FFAT motif) with the MOSPD2 (via MSP domain). Preferentially localized to the Golgi apparatus. Widely expressed during embryogenesis. The isoforms are differentially expressed during development. Isoform 1 is expressed maternally with expression gradually decreasing as development progresses, whereas expression of isoform 2 is barely detectable during the first 12 hours post-fertilization (hpf) but increases by the second day of development. The START domain recognizes ceramides and diacylglycerol lipids, interacts with membranes, and mediates the intermembrane transfer of ceramides and diacylglycerol lipids. The FFAT motif is required for interaction with VAPA, VAPB and MOSPD2. The PH domain targets the Golgi apparatus.