Dissection of the Mammalian Midbody Proteome Reveals Conserved Cytokinesis Mechanisms

Abstract

Cytokinesis is the essential process that partitions cellular contents into daughter cells. To identify and characterize cytokinesis proteins rapidly, we used a functional proteomic and comparative genomic strategy. Midbodies were isolated from mammalian cells, proteins were identified by multidimensional protein identification technology (MudPIT), and protein function was assessed in Caenorhabditis elegans. Of 172 homologs disrupted by RNA interference, 58% displayed defects in cleavage furrow formation or completion, or germline cytokinesis. Functional dissection of the midbody demonstrated the importance of lipid rafts and vesicle trafficking pathways in cytokinesis, and the utilization of common membrane cytoskeletal components in diverse morphogenetic events in the cleavage furrow, the germline, and neurons.A critical phase of cell division occurs just after segregation of the duplicated genome, when the chromosomes, cytoplasm, and organelles are partitioned to two daughter cells in a process termed cytokinesis. In animal cells, this event is driven by a cortical contraction that pinches the cell into two and requires coordination of the mitotic spindle, actin cytoskeleton, and plasma membrane. Failures in cytokinesis can cause cell death and age-related disorders or lead to a genome amplification characteristic of many cancers (1, 2). To understand the mechanisms of cytokinesis, the identity and function of proteins comprising the structures involved must be ascertained. We combined several approaches to obtain and study conserved and relevant factors, capitalizing on recent advances in proteomics and functional genomics.To identify proteins involved in cytokinesis, we examined a transient "organelle-like" structure called the midbody, first described by Flemming in 1891 as the remnant of cell division just prior to abscission (3, 4). Morphologically, the mammalian midbody is a dense structure containing microtubules derived from the spindle midzone tightly bundled by the cytokinetic furrow (5). Although no clear function has been ascribed to the midbody, it is

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Un nouveau rôle de p27KIP1dans la mitose ?

“…Une hypothèse particulièrement intéressante serait que p27 soit capable de cibler des complexes cycline/CDK vers des protéines spécifiques du midbody (comme citron-K) ou puisse inhiber l'activité de ces complexes au midbody, à un moment donné, pour réguler le processus d'abscission. De manière intéressante, lors d'un criblage protéomique réalisé afin d'identifier les protéines présentes au midbody, CDK1 et CDK4 ont effectivement été trouvées [11]. Reste à comprendre le rôle en culture [10].…”

Proteomics in human cancer research

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