The Flemmingsome reveals an ESCRT-to-membrane coupling via ALIX/syntenin/syndecan-4 required for completion of cytokinesis

Abstract

Cytokinesis requires the constriction of ESCRT-III filaments on the side of the midbody, where abscission occurs. After ESCRT recruitment at the midbody, it is not known how the ESCRT-III machinery localizes to the abscission site. To reveal actors involved in abscission, we obtained the proteome of intact, post-abscission midbodies (Flemmingsome) and identified 489 proteins enriched in this organelle. Among these proteins, we further characterized a plasma membrane-to-ESCRT module composed of the transmembrane proteoglycan syndecan-4, ALIX and syntenin, a protein that bridges ESCRT-III/ALIX to syndecans. The three proteins are highly recruited first at the midbody then at the abscission site, and their depletion delays abscission. Mechanistically, direct interactions between ALIX, syntenin and syndecan-4 are essential for proper enrichment of the ESCRT-III machinery at the abscission site, but not at the midbody. We propose that the ESCRT-III machinery must be physically coupled to a membrane protein at the cytokinetic abscission site for efficient scission, uncovering common requirements in cytokinesis, exosome formation and HIV budding.

Interplay of TRIM2 E3 Ubiquitin Ligase and ALIX/ESCRT Complex: Control of Developmental Plasticity During Early Neurogenesis

“…ALIX is involved in the regulation of the endolysosomal system through binding to endophilins and to endosomal sorting complexes required for the transport (ESCRT) proteins TSG101 and CHMP4b. Since TRIM2 appears to localize to vesicular-like structures of so-far unknown identity, this may provide a subcellular platform for functional interactions between these referred proteins [ 11 , 13 , 14 , 15 , 16 , 40 ].…”

“…Our present study strongly suggests that in Xenopus , Trim2 associates with Pdcd6ip/Alix (Programmed cell death 6 interacting protein/Apoptosis-linked gene-2 interacting protein X) and regulates neural development. Alix is a multimodular adaptor protein involved in the sorting of cargo proteins of multivesicular bodies for incorporation into vesicles and the endolysosome system [ 11 , 12 , 13 , 14 , 15 , 16 ]. Alix plays a role in the regulation of apoptosis, cell adhesion, cell division, and cytomorphology [ 17 , 18 ].…”

A Structural View on ESCRT-Mediated Abscission

“…Based on studies of syndecan-syntenin-ALIX interaction in the case of exosome formation (Baietti et al, 2012), a recent study suggested a two-phase recruitment of ESCRT-III, involving a tripartite module (ALIX-syntenin-syndecan-4) to be essential for localization and abscission. ALIX-syntenin anchors ESCRT-III to the membrane, while syndecan-4 stabilizes ESCRT-III polymers at the abscission site (Addi et al, 2020).…”

“…Proteome analysis revealed 577 proteins in purified intact midbodies of Chinese hamster ovary (CHO) cells (Skop et al, 2004) and 1730 proteins in the midbody interactome of HeLa cells (Capalbo et al, 2019). In addition, the midbody remnant in HeLa cells consisted of 1732 proteins (Addi et al, 2020). To systematically analyze cytokinesis, it is practical to break this complex process into the following discrete steps: assembly and ingression of the contractile actin ring to achieve a primary constriction leading to the formation of the intercellular bridge; rearrangement of microtubules during bridge formation; and secondary constriction of the intercellular bridge culminating in abscission (Bhutta et al, 2014).…”

Loss of coiled-coil protein Cep55 impairs abscission processes and results in p53-dependent apoptosis in developing cortex

“…The midbody has a thick central bulge flanked on either side by dense microtubule bundles. This complex structure consists of over 450 proteins that mediate midbody formation, maturation, and the final scission event, in which the midbody flanks are severed to separate the two daughter cells (Addi et al, 2020; Hu et al, 2012; Skop et al, 2004). The abscission process involves both microtubule disassembly and membrane severing, thought to be mediated by the endosomal sorting complexes required for transport (ESCRT) filaments (Connell et al, 2009; Guizetti et al, 2011).…”