Uring development, respectively [1]. MAP1S is smaller (120 kDa) and is ubiquitously expressed [2]. All three proteins share several defining features. They are synthesized as polyprotein precursors and are subsequently cleaved into a heavy and a light chain which bind to each other to form the respective MAP1 complex [1,2]. Heavy and light chains of all MAP1 proteins contain structurally and functionally conserved domains that mediate heavy chain-light chain interaction, microtubule binding, and the potential to interact with F-actin [1?]. The best characterized member of the MAP1 family is MAP1B, a 320-kDa protein which is expressed in the central nervous predominantly during development and in the peripheral nervous system throughout life [1,6]. While originally thought to be expressed mainly in neurons, MAP1B was found to be expressedin Schwann cells [7] and oligodendrocytes [8?0] as well. Consistent with its expression in the nervous system, MAP1B deficient mice display defects in brain development [11?4]. In the peripheral nervous system, MAP1B deficiency results in a reduced number of large myelinated axons, the reduced thickness of myelin sheaths, and a decrease in nerve conduction velocity in the sciatic nerve [13]. In order to elucidate molecular mechanisms that might be involved in the function of MAP1B during development we performed a search for protein interaction partners using one of the domains conserved between MAP1A, MAP1B, and MAP1S as bait. Here we show that the COOH terminus of the light chain of MAP1B interacts with a1-syntrophin, a modular adapter protein associated with the dystrophin-glycoprotein complex (DGC) [15?18]. a1-syntrophin, a 58-kD protein highly expressed in the brain, belongs to a multigene family which consists of five isoforms a1, ? and ?, c1 and c2. The syntrophins function by recruiting signaling molecules through their multiple protein interaction motifs. These consist of pleckstrin homology domains 1a, 1b, and 2 (PH1a, PH1b, PH2), a PDZ (postsynaptic density protein 95/MAP1A and MAP1B Interact with a1-Syntrophindisk large/zonula occludens-1 protein homology) domain, and the syntrophin unique domain (SU). TA 01 web a1-syntrophin associates with the DGC in the plasma membrane of several cell types via direct binding of its PH2 and SU region to dystrophin, dystrobrevin or utrophin [19,20]. The PDZ domain of a1-syntrophin binds to a variety of signaling molecules including sodium channels [21,22], neuronal nitric oxide synthase [23?5], aquaporin-4 [26,27] and serine/threonine kinases [28,29]. Mice lacking a1-syntrophin display aberrations in neuromuscular synapses with 24786787 undetectable levels of postsynaptic utrophin and reduced levels of acetylcholine receptor and acetylcholinesterase [30].Materials and Methods Ethics StatementTissues from mice were obtained in compliance with the Austrian law regulating the use of animals in biomedical hPTH (1-34) research, Tierversuchsgesetz, BGBl. Nr. 501/1989 and BGBl. I Nr. 162/ 2005. The manuscript does not include experiments on live animals. The production and culling of mice in order to obtain tissues (as performed in this manuscript) does not require approval of the Austrian Ministry of Science and Research, the governmental body regulating the use of animals in biomedical research. Wild-type and MAP1B2/2 mice were anesthetized and sacrificed by decapitation.Yeast 2-hybrid Screen and Recombinant ClonesThe Matchmaker 1662274 2-hybrid system (Clontech, Mountain View, California) was employ.Uring development, respectively [1]. MAP1S is smaller (120 kDa) and is ubiquitously expressed [2]. All three proteins share several defining features. They are synthesized as polyprotein precursors and are subsequently cleaved into a heavy and a light chain which bind to each other to form the respective MAP1 complex [1,2]. Heavy and light chains of all MAP1 proteins contain structurally and functionally conserved domains that mediate heavy chain-light chain interaction, microtubule binding, and the potential to interact with F-actin [1?]. The best characterized member of the MAP1 family is MAP1B, a 320-kDa protein which is expressed in the central nervous predominantly during development and in the peripheral nervous system throughout life [1,6]. While originally thought to be expressed mainly in neurons, MAP1B was found to be expressedin Schwann cells [7] and oligodendrocytes [8?0] as well. Consistent with its expression in the nervous system, MAP1B deficient mice display defects in brain development [11?4]. In the peripheral nervous system, MAP1B deficiency results in a reduced number of large myelinated axons, the reduced thickness of myelin sheaths, and a decrease in nerve conduction velocity in the sciatic nerve [13]. In order to elucidate molecular mechanisms that might be involved in the function of MAP1B during development we performed a search for protein interaction partners using one of the domains conserved between MAP1A, MAP1B, and MAP1S as bait. Here we show that the COOH terminus of the light chain of MAP1B interacts with a1-syntrophin, a modular adapter protein associated with the dystrophin-glycoprotein complex (DGC) [15?18]. a1-syntrophin, a 58-kD protein highly expressed in the brain, belongs to a multigene family which consists of five isoforms a1, ? and ?, c1 and c2. The syntrophins function by recruiting signaling molecules through their multiple protein interaction motifs. These consist of pleckstrin homology domains 1a, 1b, and 2 (PH1a, PH1b, PH2), a PDZ (postsynaptic density protein 95/MAP1A and MAP1B Interact with a1-Syntrophindisk large/zonula occludens-1 protein homology) domain, and the syntrophin unique domain (SU). a1-syntrophin associates with the DGC in the plasma membrane of several cell types via direct binding of its PH2 and SU region to dystrophin, dystrobrevin or utrophin [19,20]. The PDZ domain of a1-syntrophin binds to a variety of signaling molecules including sodium channels [21,22], neuronal nitric oxide synthase [23?5], aquaporin-4 [26,27] and serine/threonine kinases [28,29]. Mice lacking a1-syntrophin display aberrations in neuromuscular synapses with 24786787 undetectable levels of postsynaptic utrophin and reduced levels of acetylcholine receptor and acetylcholinesterase [30].Materials and Methods Ethics StatementTissues from mice were obtained in compliance with the Austrian law regulating the use of animals in biomedical research, Tierversuchsgesetz, BGBl. Nr. 501/1989 and BGBl. I Nr. 162/ 2005. The manuscript does not include experiments on live animals. The production and culling of mice in order to obtain tissues (as performed in this manuscript) does not require approval of the Austrian Ministry of Science and Research, the governmental body regulating the use of animals in biomedical research. Wild-type and MAP1B2/2 mice were anesthetized and sacrificed by decapitation.Yeast 2-hybrid Screen and Recombinant ClonesThe Matchmaker 1662274 2-hybrid system (Clontech, Mountain View, California) was employ.
