Cortical Constriction During Abscission Involves Helices of ESCRT-III–Dependent Filaments

Abstract

After partitioning of cytoplasmic contents by cleavage furrow ingression, animal cells remain connected by an intercellular bridge, which subsequently splits by abscission. Here, we examined intermediate stages of abscission in human cells by using live imaging, three-dimensional structured illumination microscopy, and electron tomography. We identified helices of 17-nanometer-diameter filaments, which narrowed the cortex of the intercellular bridge to a single stalk. The endosomal sorting complex required for transport (ESCRT)-III co-localized with constriction zones and was required for assembly of 17-nanometer-diameter filaments. Simultaneous spastin-mediated removal of underlying microtubules enabled full constriction at the abscission site. The identification of contractile filament helices at the intercellular bridge has broad implications for the understanding of cell division and of ESCRT-III-mediated fission of large membrane structures.

Ubiquitin-Dependent Sorting in Endocytosis

“…The ability of ESCRT-I and -II to form a supercomplex and the lack of a clear necessary role for Ub binding by ESCRT-II suggests ESCRT-I and -II function together rather than individually in sequence, as a secondary Ub-sorting receptor that receives cargo from ESCRT-0 (Amerik et al 2006;Shields et al 2009;Boura et al 2012). The idea that these work in sequence is supported by immunolocalization experiments showing a differential distribution of ESCRT-0 and ESCRT-I, live cell imaging that shows sequential assembly of ESCRTs at the sites of viral budding and cytokinesis, and biochemical studies in yeast mutants where assembly intermediates can be accumulated (Babst et al 2002;Bache et al 2003;Elia et al 2011;Guizetti et al 2011;Jouvenet et al 2011). In addition, several other proteins that are structurally related to ESCRT-0 have been proposed to work in parallel to ESCRT-0 as alternative early Ub-cargo receptors.…”

Cytokinesis in Animal Cells

“…Consistent with this, the ESCRT-III Snf7 components (known as CHMP4 proteins in humans) have been observed to form spiral filaments that appear to remodel and constrict the membrane to create the abscission site ( Fig. 1) (Elia et al 2011;Guizetti et al 2011). In human cells, ESCRT proteins are initially recruited to the midbody ring through direct interaction of Cep55 with the ESCRT-I component TSG101 and another MVB player, ALIX, which, in turn, recruits CHMP4 proteins (Carlton and Martin-Serrano 2007;Morita et al 2007).…”

Centrosomes as signalling centres

“…Of note, centriolin shares a small region of homology with the fission yeast SIN scaffolding component Cdc11 [122]. How centriolin, Cep55 and other centrosome-and midbody-associated proteins cooperate to regulate mitotic exit in human cells remains to be elucidated, but they are expected to impact on the regulation of vesicle transport and MT severing [124,125].…”