title: The acidic domain of the endothelial membrane protein GPIHBP1 stabilizes lipoprotein lipase activity by preventing unfolding of its catalytic domain.
abstract: GPIHBP1 is a glycolipid-anchored membrane protein of capillary endothelial cells that binds lipoprotein lipase (LPL) within the interstitial space and shuttles it to the capillary lumen. The LPL•GPIHBP1 complex is responsible for margination of triglyceride-rich lipoproteins along capillaries and their lipolytic processing. The current work conceptualizes a model for the GPIHBP1•LPL interaction based on biophysical measurements with hydrogen-deuterium exchange/mass spectrometry, surface plasmon resonance, and zero-length cross-linking. According to this model, GPIHBP1 comprises two functionally distinct domains: (1) an intrinsically disordered acidic N-terminal domain; and (2) a folded C-terminal domain that tethers GPIHBP1 to the cell membrane by glycosylphosphatidylinositol. We demonstrate that these domains serve different roles in regulating the kinetics of LPL binding. Importantly, the acidic domain stabilizes LPL catalytic activity by mitigating the global unfolding of LPL's catalytic domain. This study provides a conceptual framework for understanding intravascular lipolysis and GPIHBP1 and LPL mutations causing familial chylomicronemia.
authors.affiliation: Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.|Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.|Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark.
authors.forename: Simon
authors.initials: S
authors.lastname: Mysling
authors.affiliation: Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.|Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Kristian Kølby
authors.initials: KK
authors.lastname: Kristensen
authors.affiliation: Department of Medicine, University of California, Los Angeles, Los Angeles, United States.
authors.forename: Mikael
authors.initials: M
authors.lastname: Larsson
authors.affiliation: Department of Medicine, University of California, Los Angeles, Los Angeles, United States.
authors.forename: Anne P
authors.initials: AP
authors.lastname: Beigneux
authors.affiliation: Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.|Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Gårdsvoll
authors.affiliation: Department of Medicine, University of California, Los Angeles, Los Angeles, United States.
authors.forename: Loren G
authors.initials: LG
authors.lastname: Fong
authors.affiliation: Division of Nutritional Science, Cornell University, Ithaca, United States.
authors.forename: André
authors.initials: A
authors.lastname: Bensadouen
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark.
authors.forename: Thomas Jd
authors.initials: TJ
authors.lastname: Jørgensen
authors.affiliation: Department of Medicine, University of California, Los Angeles, Los Angeles, United States.|Department of Human Genetics, University of California, Los Angeles, Los Angeles, United States.
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Young
authors.affiliation: Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.|Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Ploug
mesh_terms: D000818:Animals; D020134:Catalytic Domain; D002460:Cell Line; D004795:Enzyme Stability; D006801:Humans; D007700:Kinetics; D008071:Lipoprotein Lipase / Q000737:chemistry / Q000378:metabolism*; D013058:Mass Spectrometry; D011485:Protein Binding; D011487:Protein Conformation; D000072417:Protein Domains; D017510:Protein Folding; D018110:Receptors, Lipoprotein / Q000737:chemistry / Q000378:metabolism*; D020349:Surface Plasmon Resonance
chemical_list: C523701:GPIHBP1 protein, human; D018110:Receptors, Lipoprotein; D008071:Lipoprotein Lipase
keywords: HDX-MS; biophysics; familial chylomicronemia; human; human biology; hyperlipidemia; intrinsically disordered protein; lipolysis; medicine; structural biology; surface plasmon resonance