title: Nuclear localization of Munc18-1 (p67) in the adult rat brain and PC12 cells.
abstract: Munc18-1, also referred to as p67, co-purifies with Cdk5 and has an important role in neurotransmitter release. The role of Munc18-1 for functional connectivity of the nervous system was demonstrated by gene knockout experiments in mice, wherein accumulation of neurotransmitter and silencing of synaptic activity was observed. Our earlier studies have shown that both Munc18-1 and Cdk5 co-purify and co-localize with cytoskeletal components, implying that apart from having a regulatory role in vesicle docking and fusion, Munc18-1 could also affect the dynamics of neuronal cytoskeleton. In the present study we have shown the presence of Munc18-1 in nuclear rich fraction from rat brain and confirmed the nuclear localization of this protein in PC12 cells and adult rat brain neurons by immunofluorescence and immunoelectron microscopy. We also demonstrate the binding of Munc18-1 to double stranded (ds) DNA. The ability of Munc18-1 to bind dsDNA, albeit the lack of DNA binding domains, suggests that the binding may be mediated through protein-protein interaction through some other DNA-binding proteins. The presence of both nuclear import and export signals in Munc18-1 primary structure corroborates its nuclear localization and makes it a putative shuttle protein between nuclear and cytoplasmic compartments, the precise physiological relevance of which needs to be elucidated.
authors.affiliation: Department of Neurochemistry, National Institute of Mental Health and Neurosciences, Bangalore 560 029, Karnataka, India.
authors.forename: Vandana M
authors.initials: VM
authors.lastname: Sharma
authors.forename: Momin M
authors.initials: MM
authors.lastname: Shareef
authors.forename: Kiran
authors.initials: K
authors.lastname: Bhaskar
authors.forename: Savitha
authors.initials: S
authors.lastname: Kalidas
authors.forename: Pavankumar A
authors.initials: PA
authors.lastname: Shetty
authors.forename: Rita
authors.initials: R
authors.lastname: Christopher
authors.forename: Y
authors.initials: Y
authors.lastname: Ramamohan
authors.forename: Harish C
authors.initials: HC
authors.lastname: Pant
authors.forename: Taranath K
authors.initials: TK
authors.lastname: Shetty
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000648:ultrastructure; D002451:Cell Compartmentation / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism* / Q000648:ultrastructure; D051360:Cyclin-Dependent Kinase 5; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D008297:Male; D046529:Microscopy, Electron, Transmission; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D019913:Nuclear Localization Signals / Q000378:metabolism; D016716:PC12 Cells; D017434:Protein Structure, Tertiary / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D033921:Vesicular Transport Proteins / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins; D019913:Nuclear Localization Signals; C497939:Stxbp1 protein, rat; D033921:Vesicular Transport Proteins; D004247:DNA; D051360:Cyclin-Dependent Kinase 5; C495907:Cdk5 protein, rat; D018844:Cyclin-Dependent Kinases