title: Nesprin-2 mediated nuclear trafficking and its clinical implications.
abstract: Nuclear translocation of proteins has a crucial role in the pathogenesis of cancer, Alzheimer disease and viral infections. A complete understanding of nuclear trafficking mechanisms is therefore necessary in order to establish effective intervention strategies. Here we elucidate the role of Nesprin-2 in Ca(2+)/Calmodulin mediated nuclear transport. Nesprin-2 is an actin-binding nuclear envelope (NE) protein with roles in maintaining nuclear structure and location, regulation of transcription and mechanotransduction. Upon depletion of Nesprin-2 using shRNA, HaCaT cells show abnormal localization of the shuttling proteins BRCA1 and NF-κB. We show that their nuclear transport is unlikely due to the canonical RAN mediated nuclear import, but rather to a RAN independent Ca(2+)/Calmodulin driven mechanism involving Nesprin-2. We report novel interactions between the actin-binding domain of Nesprin-2 and Calmodulin and between the NLS containing region of BRCA1 and Calmodulin. Strikingly, displacing Nesprins from the NE resulted in increased steady state Ca(2+) concentrations in the cytoplasm suggesting a previously unidentified role of Nesprins in Ca(2+) regulation. On comparing Nesprin-2 and BRCA1 localization in the ovarian cancer cell lines SKOV-3 and Caov-3, Nesprin-2 and BRCA1 were localized to the NE envelope and the nucleus in SKOV-3, respectively, and to the cytoplasm in Caov-3 cells. Fibroblasts obtained from EDMD5 (Emery Dreifuss muscular dystrophy) patients showed loss of Nesprin-2 from the nuclear envelope, corresponding reduced nuclear localization of BRCA1 and enhanced cytoplasmic Ca(2+). Taken together, the data suggests a novel role of Nesprin-2 in Ca(2+)/Calmodulin mediated nuclear trafficking and provides new insights which can guide future therapies.
authors.affiliation: a Institute for Biochemistry I; Medical Faculty; University of Cologne ; Köln , Germany.|b Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD); University of Cologne ; Köln , Germany.|c Center for Molecular Medicine; University of Cologne ; Köln , Germany.
authors.forename: Pranav
authors.initials: P
authors.lastname: Kelkar
authors.affiliation: d Institute of Vegetative Physiology; Medical Faculty; University of Cologne ; Köln ; Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Walter
authors.affiliation: d Institute of Vegetative Physiology; Medical Faculty; University of Cologne ; Köln ; Germany.
authors.forename: Symeon
authors.initials: S
authors.lastname: Papadopoulos
authors.affiliation: a Institute for Biochemistry I; Medical Faculty; University of Cologne ; Köln , Germany.|b Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD); University of Cologne ; Köln , Germany.|c Center for Molecular Medicine; University of Cologne ; Köln , Germany.
authors.forename: Carmen
authors.initials: C
authors.lastname: Mroß
authors.affiliation: a Institute for Biochemistry I; Medical Faculty; University of Cologne ; Köln , Germany.|b Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD); University of Cologne ; Köln , Germany.|c Center for Molecular Medicine; University of Cologne ; Köln , Germany.
authors.forename: Martina
authors.initials: M
authors.lastname: Munck
authors.affiliation: a Institute for Biochemistry I; Medical Faculty; University of Cologne ; Köln , Germany.|b Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD); University of Cologne ; Köln , Germany.|c Center for Molecular Medicine; University of Cologne ; Köln , Germany.
authors.forename: Vivek S
authors.initials: VS
authors.lastname: Peche
authors.affiliation: a Institute for Biochemistry I; Medical Faculty; University of Cologne ; Köln , Germany.|b Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD); University of Cologne ; Köln , Germany.|c Center for Molecular Medicine; University of Cologne ; Köln , Germany.
authors.forename: Angelika A
authors.initials: AA
authors.lastname: Noegel
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000818:Animals; D019313:BRCA1 Protein / Q000378:metabolism; D019556:COS Cells; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D002460:Cell Line; D002522:Chlorocebus aethiops; D017930:Genes, Reporter; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D008840:Microfilament Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D020389:Muscular Dystrophy, Emery-Dreifuss / Q000378:metabolism / Q000473:pathology; D016328:NF-kappa B / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D022022:Nuclear Pore / Q000378:metabolism; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D020931:ran GTP-Binding Protein / Q000378:metabolism
chemical_list: D019313:BRCA1 Protein; D002147:Calmodulin; D008565:Membrane Proteins; D008840:Microfilament Proteins; D016328:NF-kappa B; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; C485904:SYNE2 protein, human; C092710:emerin; D020931:ran GTP-Binding Protein; D002118:Calcium
keywords: BRCA1; Calmodulin; NF-κB; Nesprin-2; RAN; nuclear transport