Synaptotagmin-1 and Doc2b Exhibit Distinct Membrane-Remodeling Mechanisms

Raya Sorkin, Margherita Marchetti, Emma Logtenberg, Melissa C. Piontek, Emma Kerklingh, Guy Brand, Rashmi Voleti, Josep Rizo, Wouter H. Roos, Alexander J. Groffen, Gijs J.L. Wuite

Research output: Contribution to journalArticle

Abstract

Synaptotagmin-1 (Syt1) is a calcium sensor protein that is critical for neurotransmission and is therefore extensively studied. Here, we use pairs of optically trapped beads coated with SNARE-free synthetic membranes to investigate Syt1-induced membrane remodeling. This activity is compared with that of Doc2b, which contains a conserved C2AB domain and induces membrane tethering and hemifusion in this cell-free model. We find that the soluble C2AB domain of Syt1 strongly affects the probability and strength of membrane-membrane interactions in a strictly Ca2+- and protein-dependent manner. Single-membrane loading of Syt1 yielded the highest probability and force of membrane interactions, whereas in contrast, Doc2b was more effective after loading both membranes. A lipid-mixing assay with confocal imaging reveals that both Syt1 and Doc2b are able to induce hemifusion; however, significantly higher Syt1 concentrations are required. Consistently, both C2AB fragments cause a reduction in the membrane-bending modulus, as measured by a method based on atomic force microscopy. This lowering of the energy required for membrane deformation may contribute to Ca2+-induced fusion.

Original languageEnglish (US)
Pages (from-to)643-656
Number of pages14
JournalBiophysical journal
Volume118
Issue number3
DOIs
StatePublished - Feb 4 2020

ASJC Scopus subject areas

  • Biophysics

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    Sorkin, R., Marchetti, M., Logtenberg, E., Piontek, M. C., Kerklingh, E., Brand, G., Voleti, R., Rizo, J., Roos, W. H., Groffen, A. J., & Wuite, G. J. L. (2020). Synaptotagmin-1 and Doc2b Exhibit Distinct Membrane-Remodeling Mechanisms. Biophysical journal, 118(3), 643-656. https://doi.org/10.1016/j.bpj.2019.12.021