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Journal Articles Journal of Cell Biology Year : 2023

Human septins organize as octamer-based filaments and mediate actin-membrane anchoring in cells

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Carla Silva Martins
Cyntia Taveneau
Shizue Omi
Francois Iv
Alex Llewellyn
Mayssa Belhabib
Sophie Brasselet
Felix Rico
Gijsje Koenderink
Jérôme Wenger
Manos Mavrakis

Abstract

Septins are cytoskeletal proteins conserved from algae and protists to mammals. A unique feature of septins is their presence as heteromeric complexes that polymerize into filaments in solution and on lipid membranes. Although animal septins associate extensively with actin-based structures in cells, whether septins organize as filaments and if septin organization impacts septin function is not known. Customizing a tripartite split-GFP complementation assay, we show that all septins decorating actin stress fibers are octamer-containing filaments. Depleting octamers or preventing septins from polymerizing leads to a loss of stress fibers and reduced cell stiffness. Super-resolution microscopy revealed septin fibers with widths compatible with their organization as paired septin filaments. Nanometer-resolved distance measurements and single-protein tracking further showed that septin filaments are membrane-bound and largely immobilized. Finally, reconstitution assays on supported lipid bilayers showed that septin filaments mediate actin-membrane anchoring. We propose that septin organization as octamer-based filaments is essential for septin function in anchoring and stabilizing actin filaments at the plasma membrane.
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Dates and versions

hal-03588456 , version 1 (22-03-2022)
hal-03588456 , version 2 (03-12-2022)

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Cite

Carla Silva Martins, Cyntia Taveneau, Gerard Castro-Linares, Mikhail Baibakov, Nicolas Buzhinsky, et al.. Human septins organize as octamer-based filaments and mediate actin-membrane anchoring in cells. Journal of Cell Biology, 2023, 222 (3), pp.e202203016. ⟨10.1083/jcb.202203016⟩. ⟨hal-03588456v2⟩
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