Probable role in the clearance of triglyceride-rich lipoprotein from blood. Binds chylomicrons, LDL and VLDL in presence of free fatty acids and allows their subsequent uptake in the cells (PubMed:10224102). Maintains epithelial barrier function by recruiting MARVELD2/tricellulin to tricellular tight junctions (By similarity). Homotrimer or homotetramer constituted of isoform 1 and/or isoform 2 and isoform 3 (PubMed:10224102). Assembles into cell-cell contacts. Interacts (via the cytoplasmic domain) with MARVELD2 (via C-terminal cytoplasmic domain); the interaction is required to recruit MARVELD2 to tricellular contacts. Interacts with OCLN (By similarity). Located at tricellular contacts. Specifically expressed in liver. Also detected in kidney and lung. Phosphorylation at Ser-308 by MAPK8/JNK1 and MAPK9/JNK2 may be required for exclusive localization at tricellular tight junstions. Belongs to the immunoglobulin superfamily. LISCH7 family.