Required to generate and maintain the structure of the tubular endoplasmic reticulum network and the vacuole. Induces high curvature in membranes and causes membrane tubule formation. Involved in membrane/vesicle trafficking (By similarity). Required for the correct positioning of the cellular division plane by delimiting the actomyosin ring assembly at the cell equator (PubMed:20434336). Oligomer (By similarity). Interacts with RTN1 and TTS1. Enriched at the cell equator during mitosis. The short lumenal loops between transmembrane domains 1 and 2 and between transmembrane domains 3 and 4 may impart a wedge-like configuration, thus deforming membranes. Belongs to the DP1 family.