LAPTM4B controls the sphingolipid and ether lipid signature of small extracellular vesicles

Lysosome Associated Protein Transmembrane 4B (LAPTM4B) is a four-membrane spanning ceramide interacting protein that regulates mTORC1 signaling. Here, we show LAPTM4B sorted into intraluminal vesicles (ILVs) of multivesicular endosomes (MVEs) and released in small extracellular (sEVs) conditioned cell culture medium human urine. Efficient sorting ILV membranes depends on its third transmembrane domain containing sphingolipid interaction motif (SLim). Unbiased lipidomic analysis reveals strong enrichment glycosphingolipids sEVs secreted from knockout cells expressing SLim-deficient mutant. The altered profile accompanied by distinct SLim-dependent co-modulation ether lipid species. changes the composition derived reflected an increased stability membrane nanodomains sEVs. These results identify as determinant glycosphingolipid properties