The complexin C-terminal amphipathic helix stabilizes the fusion pore open state by sculpting membranes

• Published in: Nature structural & molecular biology Vol. 29; no. 2; pp. 97 - 107
• Main Authors: Courtney, Kevin C., Wu, Lanxi, Mandal, Taraknath, Swift, Mark, Zhang, Zhao, Alaghemandi, Mohammad, Wu, Zhenyong, Bradberry, Mazdak M., Deo, Claire, Lavis, Luke D., Volkmann, Niels, Hanein, Dorit, Cui, Qiang, Bao, Huan, Chapman, Edwin R.
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.02.2022; Nature Publishing Group
• Subjects: 101/28; 631/45/612/1237; 631/57/1481; 631/57/2270; 82/16; 82/83; 9/74; Adaptor Proteins, Vesicular Transport - chemistry; Adaptor Proteins, Vesicular Transport - genetics; Adaptor Proteins, Vesicular Transport - metabolism; Animals; Biochemistry; Biological Microscopy; Biomedical and Life Sciences; Caenorhabditis elegans Proteins - chemistry; Caenorhabditis elegans Proteins - genetics; Caenorhabditis elegans Proteins - metabolism; Drosophila Proteins - chemistry; Drosophila Proteins - genetics; Drosophila Proteins - metabolism; Electrophysiology; HEK293 Cells; Humans; Intermediates; Life Sciences; Lipid Bilayers - chemistry; Lipids; Membrane Biology; Membrane fusion; Membrane Fusion - physiology; Membrane vesicles; Membranes; Molecular Dynamics Simulation; N-Ethylmaleimide; Nerve Tissue Proteins - chemistry; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Neurotransmitter release; Neurotransmitters; Nuclear Pore - chemistry; Nuclear Pore - metabolism; Peptide Fragments - chemistry; Peptide Fragments - genetics; Peptide Fragments - metabolism; Phospholipids; Pores; Protein Conformation, alpha-Helical; Protein Stability; Protein Structure; Proteins; SNAP receptors; Structural stability; Synaptic Vesicles - chemistry; Synaptic Vesicles - metabolism; Vesicle fusion
• ISSN: 1545-9993; 1545-9985
• DOI: 10.1038/s41594-021-00716-0

Neurotransmitter release is mediated by proteins that drive synaptic vesicle fusion with the presynaptic plasma membrane. While soluble N -ethylmaleimide sensitive factor attachment protein receptors (SNAREs) form the core of the fusion apparatus, additional proteins play key roles in the fusion pathway. Here, we report that the C-terminal amphipathic helix of the mammalian accessory protein, complexin (Cpx), exerts profound effects on membranes, including the formation of pores and the efficient budding and fission of vesicles. Using nanodisc-black lipid membrane electrophysiology, we demonstrate that the membrane remodeling activity of Cpx modulates the structure and stability of recombinant exocytic fusion pores. Cpx had particularly strong effects on pores formed by small numbers of SNAREs. Under these conditions, Cpx increased the current through individual pores 3.5-fold, and increased the open time fraction from roughly 0.1 to 1.0. We propose that the membrane sculpting activity of Cpx contributes to the phospholipid rearrangements that underlie fusion by stabilizing highly curved membrane fusion intermediates. Courtney et al. found that the C-terminal amphipathic helix of a presynaptic protein, complexin, can dramatically remodel phospholipid bilayers. This activity enables complexin to increase the size and stability of SNARE-mediated fusion pores.