title: Plexin-B3 suppresses excitatory and promotes inhibitory synapse formation in rat hippocampal neurons.
abstract: Molecular mechanisms underlying synaptogenesis and synaptic plasticity have become one of the main topics in neurobiology. Increasing evidence suggests that axon guidance molecules including semaphorins and plexins participate in synapse formation and elimination. Although class B plexins are widely expressed in the brain, their role in the nervous system remains poorly characterized. We previously identified that B-plexins modulate microtubule dynamics and through this impact dendrite growth in rat hippocampal neurons. Here, we demonstrate that Plexin-B2 and Plexin-B3 are present in dendrites, but do not localize in synapses. We find that overexpression of all B-plexins leads to decreased volume of excitatory synapses, and at the same time Plexin-B1 and Plexin-B3 promote inhibitory synapse assembly. Plexin-B3 mutants revealed that these processes use different downstream pathways. While elimination of excitatory synapses is the result of Plexin-B3 binding to microtubule end binding proteins EB1 and EB3, the increase in inhibitory synapses is mediated by regulation of Ras and Rho GTPases. Overall, our findings demonstrate that Plexin-B3 contributes to regulating synapse formation.
authors.affiliation: Department of Gene Technology, Tallinn University of Technology, Tallinn, Estonia; Competence Centre for Cancer Research, Tallinn, Estonia.
authors.forename: Piret
authors.initials: P
authors.lastname: Laht
authors.affiliation: Competence Centre for Cancer Research, Tallinn, Estonia.
authors.forename: Epp
authors.initials: E
authors.lastname: Tammaru
authors.affiliation: Competence Centre for Cancer Research, Tallinn, Estonia.
authors.forename: Maarja
authors.initials: M
authors.lastname: Otsus
authors.affiliation: Department of Gene Technology, Tallinn University of Technology, Tallinn, Estonia.
authors.forename: Johan
authors.initials: J
authors.lastname: Rohtla
authors.affiliation: Department of Gene Technology, Tallinn University of Technology, Tallinn, Estonia; Competence Centre for Cancer Research, Tallinn, Estonia.
authors.forename: Liivi
authors.initials: L
authors.lastname: Tiismus
authors.affiliation: Department of Gene Technology, Tallinn University of Technology, Tallinn, Estonia; Competence Centre for Cancer Research, Tallinn, Estonia. Electronic address: andres.veske@ttu.ee.
authors.forename: Andres
authors.initials: A
authors.lastname: Veske
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005260:Female; D006624:Hippocampus / Q000166:cytology*; D008297:Male; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000502:physiology*; D016708:Synaptophysin / Q000378:metabolism
chemical_list: C489787:MAP2 protein, rat; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; C553929:Plxnb3 protein, rat; D016708:Synaptophysin; C569016:Syp protein, rat
keywords: EB3; Neurodevelopment; Neuron; Plexin; Synapse; semaphorin