Abstract
During cytokinesis, the central spindle, a bundle of interdigitated anti-parallel microtubules between separating chromosomes, recruits various cytokinetic regulator proteins to the cleavage region. Here, we show that the level of protein ubiquitylation is strikingly and transiently elevated in Aurora B kinase-positive double-band regions of the central spindle during cytokinesis. Two deubiquitylating enzymes UBPY and AMSH, which act on endosomes in interphase, were also recruited to the cleavage region. Whereas UBPY was detected only in the final stage of cytokinesis at the midbody, AMSH localized to a ring structure surrounding the mitotic kinesin MKLP1-positive region of the central spindle and midbody throughout cytokinesis. Depletion of cellular UBPY or AMSH led to defects in cytokinesis. VAMP8, a v-SNARE required for vesicle fusion in cytokinesis, localized to the central spindle region positive for ubiquitylated proteins, and underwent ubiquitylation and deubiquitylation by both UBPY and AMSH. Our results thus implicate the ubiquitylation/deubiquitylation of proteins including VAMP8 in cytokinesis.
Highlights
Animal cell cytokinesis is initiated by ingression of the cleavage furrow and completed by scission of the midbody, a narrow intercellular bridge between two daughter cells (Glotzer, 2005; Eggert et al, 2006; Barr and Gruneberg, 2007)
VAMP8, a v-SNARE required for vesicle fusion in cytokinesis, localized to the central spindle region positive for ubiquitylated proteins, and underwent ubiquitylation and deubiquitylation by both UBPY and AMSH
We demonstrate a dynamic regulation of protein ubiquitylation and deubiquitylation at the central spindle, which are implicated in cytokinesis
Summary
Animal cell cytokinesis is initiated by ingression of the cleavage furrow and completed by scission of the midbody, a narrow intercellular bridge between two daughter cells (Glotzer, 2005; Eggert et al, 2006; Barr and Gruneberg, 2007). Fusion of secretory vesicles and recycling endosomes with the plasma membrane at the cleavage furrow supplies membranes to increase the surface area of prospective daughter cells (Matheson et al, 2005; Baluska et al, 2006). Their homotypic fusion at the midbody in the final stage of cytokinesis completes abscission, a process that severs two daughter cells at the midbody, by sealing off the plasma membrane at the cytokinetic space (Matheson et al, 2005; Baluska et al, 2006). The SNARE proteins VAMP8/endobrevin and syntaxin 2 localize to the central spindle, a bundle of interdigitated anti-parallel microtubules between separating chromosomes, and play essential roles in cytokinesis (Low et al, 2003)
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