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 journalArticleAcademicpeer-review

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
Pages (from-to)643-656
Number of pages14
JournalBiophysical Journal
Volume118
Issue number3
Early online date1 Jan 2020
DOIs
Publication statusPublished - 4 Feb 2020

Cite this

Sorkin, R., Marchetti, M., Logtenberg, E., Piontek, M. C., Kerklingh, E., Brand, G., ... 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