title: Calsyntenin-3 molecular architecture and interaction with neurexin 1α.
abstract: Calsyntenin 3 (Cstn3 or Clstn3), a recently identified synaptic organizer, promotes the development of synapses. Cstn3 localizes to the postsynaptic membrane and triggers presynaptic differentiation. Calsyntenin members play an evolutionarily conserved role in memory and learning. Cstn3 was recently shown in cell-based assays to interact with neurexin 1α (n1α), a synaptic organizer that is implicated in neuropsychiatric disease. Interaction would permit Cstn3 and n1α to form a trans-synaptic complex and promote synaptic differentiation. However, it is contentious whether Cstn3 binds n1α directly. To understand the structure and function of Cstn3, we determined its architecture by electron microscopy and delineated the interaction between Cstn3 and n1α biochemically and biophysically. We show that Cstn3 ectodomains form monomers as well as tetramers that are stabilized by disulfide bonds and Ca(2+), and both are probably flexible in solution. We show further that the extracellular domains of Cstn3 and n1α interact directly and that both Cstn3 monomers and tetramers bind n1α with nanomolar affinity. The interaction is promoted by Ca(2+) and requires minimally the LNS domain of Cstn3. Furthermore, Cstn3 uses a fundamentally different mechanism to bind n1α compared with other neurexin partners, such as the synaptic organizer neuroligin 2, because Cstn3 does not strictly require the sixth LNS domain of n1α. Our structural data suggest how Cstn3 as a synaptic organizer on the postsynaptic membrane, particularly in tetrameric form, may assemble radially symmetric trans-synaptic bridges with the presynaptic synaptic organizer n1α to recruit and spatially organize proteins into networks essential for synaptic function.
authors.affiliation: the Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, the School of Life Science and Technology and Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an 710049, China.
authors.forename: Zhuoyang
authors.initials: Z
authors.lastname: Lu
authors.affiliation: the University of Michigan, Ann Arbor, Michigan 48109.
authors.forename: Yun
authors.initials: Y
authors.lastname: Wang
authors.affiliation: the University of Michigan, Ann Arbor, Michigan 48109.
authors.forename: Fang
authors.initials: F
authors.lastname: Chen
authors.affiliation: the Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720.
authors.forename: Huimin
authors.initials: H
authors.lastname: Tong
authors.affiliation: From the Department of Pharmacology and Toxicology and.
authors.forename: M V V V Sekhar
authors.initials: MV
authors.lastname: Reddy
authors.affiliation: the Department of Psychiatry, University of British Columbia, Vancouver V6T 2A1, Canada, and.
authors.forename: Lin
authors.initials: L
authors.lastname: Luo
authors.affiliation: From the Department of Pharmacology and Toxicology and.
authors.forename: Suchithra
authors.initials: S
authors.lastname: Seshadrinathan
authors.affiliation: the Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.affiliation: the Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston Texas 77555.
authors.forename: Luis Marcelo F
authors.initials: LM
authors.lastname: Holthauzen
authors.affiliation: the Department of Psychiatry, University of British Columbia, Vancouver V6T 2A1, Canada, and.
authors.forename: Ann Marie
authors.initials: AM
authors.lastname: Craig
authors.affiliation: the Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, gren@lbl.gov.
authors.forename: Gang
authors.initials: G
authors.lastname: Ren
authors.affiliation: From the Department of Pharmacology and Toxicology and the Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston Texas 77555, garudenk@utmb.edu.
authors.forename: Gabby
authors.initials: G
authors.lastname: Rudenko
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D002417:Cattle; D005110:Extracellular Space / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D051381:Rats; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism
chemical_list: C472553:CLSTN3 protein, human; D002135:Calcium-Binding Proteins; D008565:Membrane Proteins; C547193:Nrxn1 protein, rat; D011956:Receptors, Cell Surface
keywords: Calsyntenins; Cell Adhesion; Cell Surface Receptor; Neurexins; Neuropsychiatric Disorders; Protein-Protein Interaction; Single-particle Analysis; Synapse; Synaptic Organizers