title: α-Lactalbumin:Oleic Acid Complex Spontaneously Delivers Oleic Acid to Artificial and Erythrocyte Membranes.
abstract: Human α-lactalbumin made lethal to tumor cells (HAMLET) is a tumoricidal complex consisting of human α-lactalbumin and multiple oleic acids (OAs). OA has been shown to play a key role in the activity of HAMLET and its related complexes, generally known as protein-fatty acid (PFA) complexes. In contrast to what is known about the fate of the protein component of such complexes, information about what happens to OA during their action is still lacking. We monitored the membrane, OA and protein components of bovine α-lactalbumin complexed with OA (BLAOA; a HAMLET-like substance) and how they associate with each other. Using ultracentrifugation, we found that the OA and lipid components follow each other closely. We then firmly identify a transfer of OA from BLAOA to both artificial and erythrocyte membranes, indicating that natural cells respond similarly to BLAOA treatment as artificial membranes. Uncomplexed OA is unable to similarly affect membranes at the conditions tested, even at elevated concentrations. Thus, BLAOA can spontaneously transfer OA to a lipid membrane. After the interaction with the membrane, the protein is likely to have lost most or all of its OA. We suggest a mechanism for passive import of mainly uncomplexed protein into cells, using existing models for OA's effect on membranes. Our results are consistent with a membrane destabilization mediated predominantly by OA insertion being a significant contribution to PFA cytotoxicity.
authors: Department of Molecular Biology, University of Bergen, Thormøhlens Gate 55, 5008 Bergen, Norway.
authors: Hanzhen
authors: H
authors: Wen
authors: Department of Molecular Biology, University of Bergen, Thormøhlens Gate 55, 5008 Bergen, Norway.
authors: Øyvind
authors: Ø
authors: Strømland
authors: Department of Molecular Biology, University of Bergen, Thormøhlens Gate 55, 5008 Bergen, Norway. Electronic address: oyvind.halskau@uib.no.
authors: Øyvind
authors: Ø
authors: Halskau
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*; D002417:Cattle; D002463:Cell Membrane Permeability; D004910:Erythrocyte Membrane / Q000378:metabolism*; D006801:Humans; D007768:Lactalbumin / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*; D008958:Models, Molecular; D019301:Oleic Acid / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*
chemical_list: D000970:Antineoplastic Agents; C560443:BAMLET complex, Bos taurus; D019301:Oleic Acid; D007768:Lactalbumin
keywords: HAMLET; PFA complexes; cell death; fatty acids; membrane