title: Live imaging and modeling of inner nuclear membrane targeting reveals its molecular requirements in mammalian cells.
abstract: Targeting of inner nuclear membrane (INM) proteins is essential for nuclear architecture and function, yet its mechanism remains poorly understood. Here, we established a new reporter that allows real-time imaging of membrane protein transport from the ER to the INM using Lamin B receptor and Lap2β as model INM proteins. These reporters allowed us to characterize the kinetics of INM targeting and establish a mathematical model of this process and enabled us to probe its molecular requirements in an RNA interference screen of 96 candidate genes. Modeling of the phenotypes of genes involved in transport of these INM proteins predicted that it critically depended on the number and permeability of nuclear pores and the availability of nuclear binding sites, but was unaffected by depletion of most transport receptors. These predictions were confirmed with targeted validation experiments on the functional requirements of nucleoporins and nuclear lamins. Collectively, our data support a diffusion retention model of INM protein transport in mammalian cells.
authors.affiliation: Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Boni
authors.affiliation: Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany.
authors.forename: Antonio Z
authors.initials: AZ
authors.lastname: Politi
authors.affiliation: Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany.
authors.forename: Petr
authors.initials: P
authors.lastname: Strnad
authors.affiliation: Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany.
authors.forename: Wanqing
authors.initials: W
authors.lastname: Xiang
authors.affiliation: Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany.
authors.forename: M Julius
authors.initials: MJ
authors.lastname: Hossain
authors.affiliation: Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany jan.ellenberg@embl.de.
authors.forename: Jan
authors.initials: J
authors.lastname: Ellenberg
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D057054:Molecular Imaging; D009685:Nuclear Envelope / Q000235:genetics / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D000097682:Lamin B Receptor
chemical_list: D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D000097682:Lamin B Receptor; C093413:lamina-associated polypeptide 2