title: The guanine-exchange factor Ric8a binds to the Ca²⁺ sensor NCS-1 to regulate synapse number and neurotransmitter release.
abstract: The conserved Ca(2+)-binding protein Frequenin (homolog of the mammalian NCS-1, neural calcium sensor) is involved in pathologies that result from abnormal synapse number and probability of neurotransmitter release per synapse. Both synaptic features are likely to be co-regulated but the intervening mechanisms remain poorly understood. We show here that Drosophila Ric8a (a homolog of mammalian synembryn, which is also known as Ric8a), a receptor-independent activator of G protein complexes, binds to Frq2 but not to the virtually identical homolog Frq1. Based on crystallographic data on Frq2 and site-directed mutagenesis on Frq1, the differential amino acids R94 and T138 account for this specificity. Human NCS-1 and Ric8a reproduce the binding and maintain the structural requirements at these key positions. Drosophila Ric8a and Gαs regulate synapse number and neurotransmitter release, and both are functionally linked to Frq2. Frq2 negatively regulates Ric8a to control synapse number. However, the regulation of neurotransmitter release by Ric8a is independent of Frq2 binding. Thus, the antagonistic regulation of these two synaptic properties shares a common pathway, Frq2-Ric8a-Gαs, which diverges downstream. These mechanisms expose the Frq2-Ric8a interacting surface as a potential pharmacological target for NCS-1-related diseases and provide key data towards the corresponding drug design.
authors: Department of Molecular, Cellular and Developmental Neurobiology, Institute Cajal, CSIC, Avenida Dr. Arce 37, Madrid 28002, Spain.
authors: Jesús
authors: J
authors: Romero-Pozuelo
authors: Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada.
authors: Jeffrey S
authors: JS
authors: Dason
authors: Department of Molecular, Cellular and Developmental Neurobiology, Institute Cajal, CSIC, Avenida Dr. Arce 37, Madrid 28002, Spain.
authors: Alicia
authors: A
authors: Mansilla
authors: Department of Crystallography and Structural Biology, Institute of Physical-Chemistry 'Rocasolano', CSIC, Serrano 119, Madrid 28006, Spain.
authors: Soledad
authors: S
authors: Baños-Mateos
authors: Department of Biochemistry and Molecular Biology, University of Salamanca, Salamanca 37007, Spain.
authors: José L
authors: JL
authors: Sardina
authors: Department of Crystallography and Structural Biology, Institute of Physical-Chemistry 'Rocasolano', CSIC, Serrano 119, Madrid 28006, Spain.
authors: Antonio
authors: A
authors: Chaves-Sanjuán
authors: Department of Molecular, Cellular and Developmental Neurobiology, Institute Cajal, CSIC, Avenida Dr. Arce 37, Madrid 28002, Spain.
authors: Jaime
authors: J
authors: Jurado-Gómez
authors: Department of Molecular, Cellular and Developmental Neurobiology, Institute Cajal, CSIC, Avenida Dr. Arce 37, Madrid 28002, Spain.
authors: Elena
authors: E
authors: Santana
authors: Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada.
authors: Harold L
authors: HL
authors: Atwood
authors: Department of Molecular, Cellular and Developmental Neurobiology, Institute Cajal, CSIC, Avenida Dr. Arce 37, Madrid 28002, Spain Department of Biochemistry and Molecular Biology, University of Salamanca, Salamanca 37007, Spain Institute for Biomedical Research (IBSAL), Salamanca 37007, Spain.
authors: Ángel
authors: Á
authors: Hernández-Hernández
authors: Department of Crystallography and Structural Biology, Institute of Physical-Chemistry 'Rocasolano', CSIC, Serrano 119, Madrid 28006, Spain.
authors: María-José
authors: MJ
authors: Sánchez-Barrena
authors: Department of Molecular, Cellular and Developmental Neurobiology, Institute Cajal, CSIC, Avenida Dr. Arce 37, Madrid 28002, Spain aferrus@cajal.csic.es.
authors: Alberto
authors: A
authors: Ferrús
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D018360:Crystallography, X-Ray / Q000379:methods; D004330:Drosophila / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D009469:Neuromuscular Junction / Q000378:metabolism; D009435:Synaptic Transmission
chemical_list: D002135:Calcium-Binding Proteins; D029721:Drosophila Proteins; D020662:Guanine Nucleotide Exchange Factors; C561938:Ric8A protein, human
keywords: Ca2+-binding proteins; Drosophila; Synapse; X-ray crystallography