Two successive oligomeric Munc13 assemblies scaffold vesicle docking and SNARE assembly to support neurotransmitter release

Bera, Manindra; Grushin, Kirill; Sundaram, Ramalingam Venkat Kalyana; Shahanoor, Ziasmin; Chatterjee, Atrouli; Radhakrishnan, Abhijith; Lee, Seong; Padmanarayana, Murugesh; Coleman, Joseph E.; Pincet, Frédéric; Rothman, James E.; Dittman, Jeremy S.

doi:10.1101/2023.07.14.549017

Cited by 3 publications

(3 citation statements)

References 73 publications

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“…To test whether these novel crystal structures could be functionally relevant for SNAREpin assembly and for fusion, we mutated conserved amino acids at both surfaces engaged in unique subunit contacts. Consistent with this [42] such mutations in the unique contacts defining the trimer and hexamer interfaces disrupted the corresponding oligomer within crystals, profoundly reduced synaptic function in Caenorhabditis elegans and resulted in docked vesicles produced in vitro that failed to be released by Ca ++ which had few if any detectable SNAREpins, employing a complete reconstitution that is Munc13-and DAGdependent [43].…”

Section: Different Munc13 Scaffolds Likely Assemble Peripheral and Ce...mentioning

confidence: 66%

Turbocharging synaptic transmission

Rothman,

Grushin,

Bera

et al. 2023

FEBS Letters

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Evidence from biochemistry, genetics, and electron microscopy strongly supports the idea that a ring of Synaptotagmin is central to the clamping and release of synaptic vesicles (SVs) for synchronous neurotransmission. Recent direct measurements in cell‐free systems suggest there are 12 SNAREpins in each ready‐release vesicle, consisting of six peripheral and six central SNAREpins. The six central SNAREpins are directly bound to the Synaptotagmin ring, are directly released by Ca++, and they initially open the fusion pore. The six peripheral SNAREpins are indirectly bound to the ring, each linked to a central SNAREpin by a bridging molecule of Complexin. We suggest that the primary role of peripheral SNAREpins is to provide additional force to ‘turbocharge’ neurotransmitter release, explaining how it can occur much faster than other forms of membrane fusion. The SV protein Synaptophysin forms hexamers that bear two copies of the v‐SNARE VAMP at each vertex, one likely assembling into a peripheral SNAREpin and the other into a central SNAREpin.

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Section: Different Munc13 Scaffolds Likely Assemble Peripheral and Ce...mentioning

confidence: 66%

Turbocharging synaptic transmission

Rothman,

Grushin,

Bera

et al. 2023

FEBS Letters

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“…The Munc13-1 nano-assembles were observed at the active zone which in turn can control the number of release sites [69][70][71] . The direct pore modulatory action of Munc13-1 is also dependent on its self-oligomerization 60,72 at the release site and on its interaction with the N-terminal regulatory domain of Syntaxin1a 56 .…”

Section: Discussionmentioning

confidence: 99%

“…indicating the importance of Munc13-1's oligomerization in yielding functional fusion pore assembly 60,61 .…”

Section: Munc13-1 and Munc18-1 Synchronize Vesicular Secretion At The...mentioning

confidence: 99%

Differential SNARE chaperoning by Munc13-1 and Munc18-1 dictates fusion pore fate at the release site

Bhaskar,

Yadav,

Sriram

et al. 2024

Nat Commun

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The regulated release of chemical messengers is crucial for cell-to-cell communication; abnormalities in which impact coordinated human body function. During vesicular secretion, multiple SNARE complexes assemble at the release site, leading to fusion pore opening. How membrane fusion regulators act on heterogeneous SNARE populations to assemble fusion pores in a timely and synchronized manner, is unknown. Here, we demonstrate the role of SNARE chaperones Munc13-1 and Munc18-1 in rescuing individual nascent fusion pores from their diacylglycerol lipid-mediated inhibitory states. At the onset of membrane fusion, Munc13-1 clusters multiple SNARE complexes at the release site and synchronizes release events, while Munc18-1 stoichiometrically interacts with trans-SNARE complexes to enhance N- to C-terminal zippering. When both Munc proteins are present simultaneously, they differentially access dynamic trans-SNARE complexes to regulate pore properties. Overall, Munc proteins’ direct action on fusion pore assembly indicates their role in controlling quantal size during vesicular secretion.

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Diacylglycerol-dependent hexamers of the SNARE-assembling chaperone Munc13-1 cooperatively bind vesicles

Li,

Grushin,

Coleman

et al. 2023

Proc. Natl. Acad. Sci. U.S.A.

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Munc13-1 is essential for vesicle docking and fusion at the active zone of synapses. Here, we report that Munc13-1 self-assembles into molecular clusters within diacylglycerol-rich microdomains present in phospholipid bilayers. Although the copy number of Munc13-1 molecules in these clusters has a broad distribution, a systematic Poisson analysis shows that this is most likely the result of two molecular species: monomers and mainly hexameric oligomers. Each oligomer is able to capture one vesicle independently. Hexamers have also been observed in crystals of Munc13-1 that form between opposed phospholipid bilayers [K. Grushin, R. V. Kalyana Sundaram, C. V. Sindelar, J. E. Rothman, Proc. Natl. Acad. Sci. U.S.A. 119 , e2121259119 (2022)]. Mutations targeting the contacts stabilizing the crystallographic hexagons also disrupt the isolated hexamers, suggesting they are identical. Additionally, these mutations also convert vesicle binding from a cooperative to progressive mode. Our study provides an independent approach showing that Munc13-1 can form mainly hexamers on lipid bilayers each capable of vesicle capture.

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Two successive oligomeric Munc13 assemblies scaffold vesicle docking and SNARE assembly to support neurotransmitter release

Cited by 3 publications

References 73 publications

Turbocharging synaptic transmission

Turbocharging synaptic transmission

Differential SNARE chaperoning by Munc13-1 and Munc18-1 dictates fusion pore fate at the release site

Diacylglycerol-dependent hexamers of the SNARE-assembling chaperone Munc13-1 cooperatively bind vesicles

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