title: Death Receptor 5 Networks Require Membrane Cholesterol for Proper Structure and Function.
abstract: Death receptor 5 (DR5) is an apoptosis-inducing member of the tumor necrosis factor receptor superfamily, whose activity has been linked to membrane cholesterol content. Upon ligand binding, DR5 forms large clusters within the plasma membrane that have often been assumed to be manifestations of receptor co-localization in cholesterol-rich membrane domains. However, we have recently shown that DR5 clusters are more than just randomly aggregated receptors. Instead, these are highly structured networks held together by receptor dimers. These dimers are stabilized by specific transmembrane helix-helix interactions, including a disulfide bond in the long isoform of the receptor. The complex relationships among DR5 network formation, transmembrane helix dimerization, membrane cholesterol, and receptor activity has not been established. It is unknown whether the membrane itself plays an active role in driving DR5 transmembrane helix interactions or in the formation of the networks. We show that cholesterol depletion in cells does not inhibit the formation of DR5 networks. However, the networks that form in cholesterol-depleted cells fail to induce caspase cleavage. These results suggest a potential structural difference between active and inactive networks. As evidence, we show that cholesterol is necessary for the covalent dimerization of DR5 transmembrane domains. Molecular simulations and experiments in synthetic vesicles on the DR5 transmembrane dimer suggest that dimerization is facilitated by increased helicity in a thicker bilayer.
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, Twin Cities, Minneapolis, MN 55455, USA.
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Lewis
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, Twin Cities, Minneapolis, MN 55455, USA.
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Valley
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, Twin Cities, Minneapolis, MN 55455, USA.
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Peery
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, Twin Cities, Minneapolis, MN 55455, USA.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Brummel
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, Twin Cities, Minneapolis, MN 55455, USA.
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Braun
authors.affiliation: Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Twin Cities, Minneapolis, MN 55455, USA.
authors.forename: Christine B
authors.initials: CB
authors.lastname: Karim
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, Twin Cities, Minneapolis, MN 55455, USA. Electronic address: jnsachs@umn.edu.
authors.forename: Jonathan N
authors.initials: JN
authors.lastname: Sachs
mesh_terms: D020169:Caspases / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D008563:Membrane Lipids / Q000378:metabolism*; D008954:Models, Biological; D011487:Protein Conformation; D055503:Protein Multimerization; D059748:Proteolysis; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D008563:Membrane Lipids; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D002784:Cholesterol; D020169:Caspases
keywords: cholesterol-rich membrane domains; disulfide bond; ligand/receptor clustering; replica exchange molecular dynamics; transmembrane domain