CryoET shows cofilactin filaments inside the microtubule lumen.

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Authors
Ventura Santos, Camilla  ORCID logo  https://orcid.org/0000-0002-4406-5151
Abstract

Cytoplasmic microtubules are tubular polymers that can harbor small proteins or filaments inside their lumen. The identities of these objects and mechanisms for their accumulation have not been conclusively established. Here, we used cryogenic electron tomography of Drosophila S2 cell protrusions and found filaments inside the microtubule lumen, which resemble those reported recently in human HAP1 cells. The frequency of these filaments increased upon inhibition of the sarco/endoplasmic reticulum Ca2+ ATPase with the small molecule drug thapsigargin. Subtomogram averaging showed that the luminal filaments adopt a helical structure reminiscent of cofilin-bound actin (cofilactin). Consistent with this, we observed cofilin dephosphorylation, an activating modification, in cells under the same conditions that increased luminal filament occurrence. Furthermore, RNA interference knock-down of cofilin reduced the frequency of luminal filaments with cofilactin morphology. These results suggest that cofilin activation stimulates its accumulation on actin filaments inside the microtubule lumen.

Description

Funder: Cambridge Trust (Cambridge Commonwealth, European & International Trust); doi: http://dx.doi.org/10.13039/501100003343

Keywords
cofilactin, cryoET, luminal filaments, microtubules, Humans, Cytoskeleton, Actin Cytoskeleton, Actins, Actin Depolymerizing Factors, Microtubules
Journal Title
EMBO Rep
Conference Name
Journal ISSN
1469-221X
1469-3178
Volume Title
Publisher
Springer Science and Business Media LLC
Sponsorship
HHS | NIH | National Institute of Neurological Disorders and Stroke (NINDS) (R21NS125795)
UKRI | Medical Research Council (MRC) (MC_UP_A025_1011)
Wellcome Trust (WT) (210711/Z/18/Z)