Gatekeeper helix activates Golgi SM protein Sly1 and directly mediates close-range vesicle tethering

Duan, M.; Plemel, R. L.; Takenaka, T.; Lin, A.; Delgado, B. M.; Nattermann, U.; Nickerson, D. P.; Mima, J.; Miller, E. A.; Merz, A. J.

doi:10.1101/2020.01.16.906719

bioRxiv · 10.1101/2020.01.16.906719

Gatekeeper helix activates Golgi SM protein Sly1 and directly mediates close-range vesicle tethering

Duan, M.·Plemel, R. L.·Takenaka, T.·Lin, A.·Delgado, B. M.·Nattermann, U.·Nickerson, D. P.·Mima, J.·Miller, E. A.·Merz, A. J.

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Abstract

The essential Golgi protein Sly1 is a member of the SM (Sec1/mammalian Unc-18) family of SNARE chaperones. Sly1 was originally identified through gain-of-function alleles that bypass requirements for diverse vesicle tethering factors. Employing genetic analyses and chemically defined reconstitutions of ER-Golgi fusion, we discovered that a loop conserved among Sly1 family members is not only autoinhibitory, but also acts as a positive effector. An amphipathic helix within the loop directly binds high-curvature membranes; membrane binding is required for relief of Sly1 autoinhibition and allows Sly1 to directly tether incoming vesicles to the Qa-SNARE on the target organelle. The SLY1-20 allele bypasses requirements for diverse tethering factors but loses this functionality if Sly1 membrane binding is impaired. We propose that long-range tethers, including Golgins and multisubunit tethering complexes, hand off vesicles to Sly1, which then tethers at close range to activate SNARE assembly and fusion in the early secretory pathway.

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Duan, M., Plemel, R. L., Takenaka, T., Lin, A., Delgado, B. M., Nattermann, U., Nickerson, D. P., Mima, J., Miller, E. A., Merz, A. J.. 2020-01-16. Gatekeeper helix activates Golgi SM protein Sly1 and directly mediates close-range vesicle tethering. https://doi.org/10.1101/2020.01.16.906719

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