Functional synergy between the Munc13 C-terminal C1 and C2 domains
Xiaoxia Liu,
Alpay Burak Seven,
Marcial Camacho,
Victoria Esser,
Junjie Xu,
Thorsten Trimbuch,
Bradley Quade,
Lijing Su,
Cong Ma,
Christian Rosenmund,
Josep Rizo
Affiliations
Xiaoxia Liu
Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States; Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States; Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
Alpay Burak Seven
Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States; Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States; Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
Marcial Camacho
Department of Neurophysiology, NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany
Victoria Esser
Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States; Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States; Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
Junjie Xu
Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States; Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States; Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
Thorsten Trimbuch
Department of Neurophysiology, NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany
Bradley Quade
Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States; Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States; Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
Lijing Su
Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States; Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States; Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
Key Laboratory of Molecular Biophysics of the Ministry of Education, Huazhong University of Science and Technology, Wuhan, China; College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
Christian Rosenmund
Department of Neurophysiology, NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany
Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States; Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States; Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
Neurotransmitter release requires SNARE complexes to bring membranes together, NSF-SNAPs to recycle the SNAREs, Munc18-1 and Munc13s to orchestrate SNARE complex assembly, and Synaptotagmin-1 to trigger fast Ca2+-dependent membrane fusion. However, it is unclear whether Munc13s function upstream and/or downstream of SNARE complex assembly, and how the actions of their multiple domains are integrated. Reconstitution, liposome-clustering and electrophysiological experiments now reveal a functional synergy between the C1, C2B and C2C domains of Munc13-1, indicating that these domains help bridging the vesicle and plasma membranes to facilitate stimulation of SNARE complex assembly by the Munc13-1 MUN domain. Our reconstitution data also suggest that Munc18-1, Munc13-1, NSF, αSNAP and the SNAREs are critical to form a ‘primed’ state that does not fuse but is ready for fast fusion upon Ca2+ influx. Overall, our results support a model whereby the multiple domains of Munc13s cooperate to coordinate synaptic vesicle docking, priming and fusion.
