Functional characterization of the interaction between Bex2 and torsinA, a protein involved in early-onset torsion dystonia der Fakultät für Biologie der EBERHARD KARLS UNIVERSITÄT TÜBINGEN zur Erlangung des Grades eines Doktors der Naturwissenschaften von Susann Horn aus Werdau vorgelegte Dissertation 2007 Tag der mündlichen Prüfung: 25.07.2007 Dekan: Prof. Dr. F. Schöffl 1. Berichterstatter: Prof. Dr. T. Gasser 2. Berichterstatter: Prof. Dr. O. Rieß Teile dieser Studie wurden bereits veröffentlicht: Wissenschaftliche Publikationen: Horn, S., Kullmann, S., Hewett, J. W., Gasser, T., and Kamm, C. (2007) The early- onset torsion dystonia protein torsinA interacts with Bex2 at the nuclear envelope. Manuscript submitted. Grundmann K., Reischmann B., Vanhoutte, G., Huebner, J., Teismann, P., Hauser, T. K., Bonin, M., Wilbertz, J., Horn, S., Nguyen, H. P., Kuhn, M., Chanarat, S., Wolburg, H., Van der Linden, A., and Riess, O. (2007) Overexpression of human wildtype torsinA and human ΔGAG torsinA in a transgenic mouse model causes phenotypic abnormalities. Neurobiol. Dis. doi:10.1016/j.nbd.2007.04.015 Tagungsbeiträge: Poster Horn, S., Kullmann, S., Hewett, J. W., Gasser, T., and Kamm, C. The early-onset torsion dystonia protein torsinA interacts with Bex2. Society for Neuroscience 36th Annual Meeting, Atlanta 2006. Meiner Familie gewidmet Content 1 SUMMARY ..................................................................................1 2 INTRODUCTION .........................................................................3 2.1 Definition and classification of dystonia.................................................. 3 2.2 Primary dystonia ........................................................................................ 6 2.3 Predominantly generalized dystonia – EOTD .......................................... 7 2.4 TorsinA – structure and expression......................................................... 8 2.5 TorsinA - putative functions.................................................................... 12 2.5.1 TorsinA in the endoplasmic reticulum.............................................. 12 2.5.2 TorsinA – an AAA+ protein with chaperone function ........................ 15 2.5.3 TorsinA at the nuclear envelope (NE).............................................. 16 2.5.4 TorsinA in dopaminergic neurons .................................................... 18 2.5.5 TorsinA, cell polarity and the cytoskeleton....................................... 19 2.6 Mouse models of early onset torsion dystonia ..................................... 20 2.7 TorsinA interactors .................................................................................. 22 2.7.1 TorsinB ............................................................................................ 22 2.7.2 Kinesin-I........................................................................................... 23 2.7.3 Vimentin........................................................................................... 24 2.7.4 LAP1 and LULL1 ............................................................................. 25 2.8 Objectives ................................................................................................. 26 2.8.1 Preliminary work .............................................................................. 26 2.8.2 Goals of this study ........................................................................... 27 3 RESULTS ..................................................................................29 3.1 Characterization of the polyclonal Bex2 antibody ................................ 29 3.2 Expression of Bex2 and torsinA in mammalian tissues and cell lines........................................................................................................... 32 3.3 Bex2 and torsinA interact in in vitro affinity precipitation assays....... 35 3.4 Bex2 and torsinA co-localize at the NE and in processes of neuron-like cells....................................................................................... 39 3.5 Bex2 and torsinA accumulation in the membranous fraction of mouse neuroblastoma cells .................................................................... 42 3.6 Bex2 and torsinA are associated with synaptosomal membranes in the mammalian brain ........................................................................... 45 3.7 Bex2, torsinA and kinesin-I co-localize in primary cortical rat neurons ..................................................................................................... 47 3.8 Characterization of hBex2 deletion variants.......................................... 51 3.9 Bex2 and torsinA are similarly distributed throughout adult rat brain .......................................................................................................... 55 3.10 TorsinA and Bex2 co-localization in neurons of adult rat brain .......... 59 i Content 4 DISCUSSION.............................................................................61 4.1 The polyclonal Bex2 antibody specifically recognizes Bex2 ............... 61 4.2 Bex2 interacts with wildtype and EOTD-causing torsinA in vitro........ 64 4.3 Bex2 and torsinA co-localize at the NE of neuronl-like cells ............... 66 4.4 Bex2 and TorsinA are associated with synaptosomal membranes..... 68 4.5 Expression of Bex2 and torsinA in neurons of the adult rat brain ...... 70 4.6 hBex2 deletions........................................................................................ 71 4.7 The role of Bex1 in neurotrophin signaling, the cell cycle and neuronal differentiation – putative functions for Bex2? ....................... 73 4.8 Orientation of Bex2 and torsinA at cellular membranes....................... 76 4.9 Conclusion................................................................................................ 78 4.10 Outlook...................................................................................................... 79 5 MATERIALS AND METHODS ..................................................83 5.1 Equipment and consumables ................................................................. 83 5.1.1 Molecular biology............................................................................. 83 5.1.2 Protein biochemistry ........................................................................ 83 5.1.3 Cell biology...................................................................................... 84 5.2 Chemicals and solutions ......................................................................... 84 5.2.1 Molecular biology............................................................................. 87 5.2.2 Protein biochemistry ........................................................................ 87 5.2.3 Cell biology...................................................................................... 89 5.3 Antibodies................................................................................................. 90 5.4 Expression and cloning vectors ............................................................. 92 5.5 Oligonucleotides ...................................................................................... 93 5.6 Methods in molecular biology................................................................. 94 5.6.1 Polymerase chain reaction (PCR) ................................................... 94 5.6.2 Reverse transcriptase PCR (RT-PCR) ............................................ 94 5.6.3 Quantitative Real time PCR (qRT-PCR).......................................... 95 5.6.4 Agarose gel electrophoresis ............................................................ 97 5.6.5 Isolation and purification of DNA-fragments .................................... 97 5.6.6 Enzymatic digestion of DNA ............................................................ 97 5.6.7 Ligation of DNA ............................................................................... 98 5.6.8 Transformation of DNA into One Shot® TOP10Electrocomp™ E. coli .............................................................................................. 98 5.6.9 Production of bacterial glycerol stocks ............................................ 98 5.6.10 Production of electrocompetent cells............................................... 98 5.6.11 Preparation and purification of plasmid DNA................................... 99 5.7 Methods in protein biochemistry.......................................................... 100 5.7.1 Preparation of protein extracts....................................................... 100 ii Content 5.7.2 Protein quantification by Bradford and Bicinchoninic Acid Assay (BCA) ............................................................................................ 100 5.7.3 SDS-polyacrylamid gel electrophoresis (PAGE)............................ 101 5.7.4 Immunoblotting .............................................................................. 102 5.7.5 Stripping of PVDF and nitrocellulose membranes ......................... 102 5.7.6 Coomassie staining of polyacrylamid gels..................................... 102 5.7.7 Ponceau S staining of PVDF- and nitrocellulose membranes ....... 103 5.7.8 Expression and purification of MBP fusion proteins....................... 103 5.7.9 Affinity precipitation assays (pull down)......................................... 104 5.7.10 Co-Immunoprecipitation assay ...................................................... 106 5.7.11 Subcellular fractionation assay.....................................................