title: Regulation of nuclear envelope permeability in cell death and survival.
abstract: The nuclear pore complex (NPC) mediates macromolecular exchange between nucleus and cytoplasm. It is a regulated channel whose functional properties are modulated in response to the physiological status of the cell. Identifying the factors responsible for regulating NPC activity is crucial to understand how intracellular signaling cues are integrated at the level of this channel to control nucleocytoplasmic trafficking. For proteins lacking active translocation signals the NPC acts as a molecular sieve limiting passage across the nuclear envelope (NE) to proteins with a MW below ~40 kD. Here, we investigate how this permeability barrier is altered in paradigms of cell death and cell survival, i.e., apoptosis induction via staurosporine, and enhanced viability via overexpression of Bcl-2. We monitor dynamic changes of the NPC's size-exclusion limit for passive diffusion by confocal time-lapse microscopy of cells undergoing apoptosis, and use different diffusion markers to determine how Bcl-2 expression affects steady-state NE permeability. We show that staurosporine triggers an immediate and gradual leakiness of the NE preceding the appearance of apoptotic hallmarks. Bcl-2 expression leads to a constitutive increase in NE permeability, and its localization at the NE is sufficient for the effect, evincing a functional role for Bcl-2 at the nuclear membrane. In both settings, NPC leakiness correlates with reduced Ca²⁺ in internal stores, as demonstrated by fluorometric measurements of ER/NE Ca²⁺ levels. By comparing two cellular models with opposite outcome these data pinpoint ER/NE Ca²⁺ as a general and physiologically relevant regulator of the permeability barrier function of the NPC.
authors.affiliation: Bioimaging Center, Department of Biology, University of Konstanz, Konstanz, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Strasser
authors.forename: Patricia
authors.initials: P
authors.lastname: Grote
authors.forename: Karin
authors.initials: K
authors.lastname: Schäuble
authors.forename: Magdalena
authors.initials: M
authors.lastname: Ganz
authors.forename: Elisa
authors.initials: E
authors.lastname: Ferrando-May
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects*; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D018613:Microscopy, Confocal; D009685:Nuclear Envelope / Q000378:metabolism*; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D019311:Staurosporine / Q000378:metabolism / Q000633:toxicity*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism / Q000633:toxicity
chemical_list: C079377:NUP153 protein, human; D028861:Nuclear Pore Complex Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D053221:TNF-Related Apoptosis-Inducing Ligand; D019311:Staurosporine; D002118:Calcium