Gth a1-syntrophin cDNA (see above) as template and primers 59-ACTGGAATTCCGCCGCGTGACGGTGCGCAAGGC-39 and 59ATCGCTCGAGCTTCATGTACTTAACCTCCAACACAACCTCCTTGCCTGTCTTC-39. The resulting PCR fragment was inserted by blunt end ligation into the EcoRV site of pBluescript (Fermentas, Glen Burnie, Maryland), cut out with EcoRI and XhoI and inserted into plasmid pGEX-4T-1 (GE Healthcare Biosciences AB, Uppsala, Sweden) to yield a construct for the expression of the NH2-terminally GST-tagged PDZ domain of a1-syntrophin. For expression in vertebrate cells we used a construct encoding COOH-terminally myc-tagged LC1 described previously [5]. For the expression of a1-syntrophin we fused the MunI/XhoI fragment of pQEsyn encoding full length a1-syntrophin (see above) in frame to NH2-terminal GFP in an EcoRI/XhoI restricted derivative of pEGFP-C1 (Clontech) which IPI549 contains a human cytomegalovirus immediate early promoter. The correct sequence of all constructs was confirmed.AntibodiesAffinity-purified rabbit polyclonal anti-LC1 antibody [5] and anti-HC1 antibody (anti-HC750) [33]; affinity-purified rabbit polyclonal anti-myc [5]; monoclonal pan anti-syntrophin antibody anti-syn1351 [34]; polyclonal rabbit anti-DRP2 [35] kindly provided by P. Brophy; polyclonal rabbit anti-paranodin antibody SL51 [36] kindly provided by J. A. Girault; polyclonal rabbit antiezrin (Upstate, Lake Placid, NY); monoclonal mouse anti-atubulin B-5-1-2 (Sigma, St. Louis, MO) and monoclonal rat antia-tubulin (YL1-2; Abcam, Cambridge, UK); Secondary antibodies: Alexa Fluor 488- or Fluor 568-labelled goat anti-rabbit, anti-rat, or anti-mouse (Molecular Probes, Leiden, The Netherlands), rhodamine-red-labeled goat anti-mouse or anti-rabbit (Jackson, West Grove, PA) and Cy5-labelled donkey anti-rat (Jackson). Secondary antibodies for immunoblots: HRP-conjugated goat anti-rabbit or anti-mouse (Jackson) or alkaline phosphaMAP1A and MAP1B Interact with a1-SyntrophinFigure 1. The light chains of MAP1B and MAP1A interact with a1-syntrophin. a) Schematic representation of MAP1B, MAP1A, and a1syntrophin to indicate the relevant domains. The drawings are not to scale. Numbers indicate amino acid positions for rat MAP1A [71,72], rat MAP1B (according to database entry XM_215469), and mouse a1-syntrophin [16,32]. MAP1B and MAP1A are 24272870 synthesized as polyprotein precursors which are proteolytically MedChemExpress JNJ-7706621 cleaved to yield heavy chains (HC1 and HC2, respectively) and light chains (LC1 and LC2, starting at residue 2212 and 2778 of the polyprotein precursor, respectively). NT-HC1, NH2 terminus of HC1; CT-LC1, COOH terminus of LC1; PH1a, PH1b, and PH2, pleckstrin homology domains; PDZ, postsynaptic density protein 95/disk large/zonula occludens-1 protein homology domain; SU, syntrophin unique domain; b) Microtiter plates coated with 100 nM recombinant LC1 (LC1) or BSA (BSA) were overlaid with increasing concentrations of Eu3+-labeled recombinant a1syntrophin. a1-syntrophin was found to bind specifically to LC1, whereas binding to BSA was weak and considered to be unspecific background of the assay. The values represent the mean 6 standard deviation of three independent experiments. c) The indicated recombinant proteins were subjected to SDS-PAGE, stained with Coomassie brilliant blue or blotted onto nitrocellulose and probed with recombinant a1-syntrophin protein. For immunological detection of syntrophin bound to blotted proteins the pan-syntrophin antibody (anti-syn1351) was used. Syntrophin was found to bind to L.Gth a1-syntrophin cDNA (see above) as template and primers 59-ACTGGAATTCCGCCGCGTGACGGTGCGCAAGGC-39 and 59ATCGCTCGAGCTTCATGTACTTAACCTCCAACACAACCTCCTTGCCTGTCTTC-39. The resulting PCR fragment was inserted by blunt end ligation into the EcoRV site of pBluescript (Fermentas, Glen Burnie, Maryland), cut out with EcoRI and XhoI and inserted into plasmid pGEX-4T-1 (GE Healthcare Biosciences AB, Uppsala, Sweden) to yield a construct for the expression of the NH2-terminally GST-tagged PDZ domain of a1-syntrophin. For expression in vertebrate cells we used a construct encoding COOH-terminally myc-tagged LC1 described previously [5]. For the expression of a1-syntrophin we fused the MunI/XhoI fragment of pQEsyn encoding full length a1-syntrophin (see above) in frame to NH2-terminal GFP in an EcoRI/XhoI restricted derivative of pEGFP-C1 (Clontech) which contains a human cytomegalovirus immediate early promoter. The correct sequence of all constructs was confirmed.AntibodiesAffinity-purified rabbit polyclonal anti-LC1 antibody [5] and anti-HC1 antibody (anti-HC750) [33]; affinity-purified rabbit polyclonal anti-myc [5]; monoclonal pan anti-syntrophin antibody anti-syn1351 [34]; polyclonal rabbit anti-DRP2 [35] kindly provided by P. Brophy; polyclonal rabbit anti-paranodin antibody SL51 [36] kindly provided by J. A. Girault; polyclonal rabbit antiezrin (Upstate, Lake Placid, NY); monoclonal mouse anti-atubulin B-5-1-2 (Sigma, St. Louis, MO) and monoclonal rat antia-tubulin (YL1-2; Abcam, Cambridge, UK); Secondary antibodies: Alexa Fluor 488- or Fluor 568-labelled goat anti-rabbit, anti-rat, or anti-mouse (Molecular Probes, Leiden, The Netherlands), rhodamine-red-labeled goat anti-mouse or anti-rabbit (Jackson, West Grove, PA) and Cy5-labelled donkey anti-rat (Jackson). Secondary antibodies for immunoblots: HRP-conjugated goat anti-rabbit or anti-mouse (Jackson) or alkaline phosphaMAP1A and MAP1B Interact with a1-SyntrophinFigure 1. The light chains of MAP1B and MAP1A interact with a1-syntrophin. a) Schematic representation of MAP1B, MAP1A, and a1syntrophin to indicate the relevant domains. The drawings are not to scale. Numbers indicate amino acid positions for rat MAP1A [71,72], rat MAP1B (according to database entry XM_215469), and mouse a1-syntrophin [16,32]. MAP1B and MAP1A are 24272870 synthesized as polyprotein precursors which are proteolytically cleaved to yield heavy chains (HC1 and HC2, respectively) and light chains (LC1 and LC2, starting at residue 2212 and 2778 of the polyprotein precursor, respectively). NT-HC1, NH2 terminus of HC1; CT-LC1, COOH terminus of LC1; PH1a, PH1b, and PH2, pleckstrin homology domains; PDZ, postsynaptic density protein 95/disk large/zonula occludens-1 protein homology domain; SU, syntrophin unique domain; b) Microtiter plates coated with 100 nM recombinant LC1 (LC1) or BSA (BSA) were overlaid with increasing concentrations of Eu3+-labeled recombinant a1syntrophin. a1-syntrophin was found to bind specifically to LC1, whereas binding to BSA was weak and considered to be unspecific background of the assay. The values represent the mean 6 standard deviation of three independent experiments. c) The indicated recombinant proteins were subjected to SDS-PAGE, stained with Coomassie brilliant blue or blotted onto nitrocellulose and probed with recombinant a1-syntrophin protein. For immunological detection of syntrophin bound to blotted proteins the pan-syntrophin antibody (anti-syn1351) was used. Syntrophin was found to bind to L.