Cellular reprogramming during cell cycle progression

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OVERVIEW OF THE PROBLEMATICThe preparation of eukaryotic cells for division requires an extensive cellular reorganization, affecting cytoskeletal elements, chromatin, and organelles. These changes in cellular architecture ensure the proper segregation of chromosomes and inheritance of organelles. Defects in mitotic reorganization can affect mitotic entry, chromosome segregation, organelle inheritance, and cell fate. At mitosis entry, cells round up to generate optimal cell geometry for mitotic spindle assembly and cytokinesis. These changes are, for the most part, regulated by the central cell cycle regulator Cdk1, which controls many events affecting cell shape and cell adherence. While Cdk1 regulates nearly all intracellular events occurring during mitosis, much less is known about its potential impact at the cell surface. As with other cellular compartments, the plasma membrane undergoes dramatic reshaping at the onset of mitosis, but the global function of these changes is poorly known. While mitotic cell rounding is not fully understood, it appears to be driven by changes in the actin cytoskeleton and by the downregulation of adhesive systems. Some receptors were shown to be depleted from the surface of mitotic cells, but a more global analysis would be required to fully understand the role and regulation of cell surface proteins during mitosis.OBJECTIVESPlasma membrane proteins have been historically understudied because of technical limitations. Chemoproteomic techniques that target the cell surface proteome (i.e., surfaceome) have begun to overcome these limitations by providing comprehensive analyses of surface-accessible protein domains. We have adapted this technology to study the role of cell surface proteins in mitosis, and have two main goals for this project:1) We want to generate high-resolution surfaceome maps of cells at different phases of the cell cycle. In this aim, we will use proteomic approaches, biochemical and cellular assays, to monitor cell-surface proteins during the cell cycle.2) We want to determine the biological significance of cell-surface changes as they relate to mitosis. In this aim, we will use cell-biological methods and microscopy to study the role of cell-surface proteins in mitosis.NOVELTY and EXPECTED SIGNIFICANCE OF THE WORKUsing innovative approaches in proteomics, we expect to uncover the precise changes that occur at the cell surface during the cell cycle. These data will help define how mitotic cells reorganize the cell surface, and will likely reveal important information about this basic biological process.Our results will be a resource for our lab and the scientific community, and will likely stimulate new investigation paths for years to come. This project will provide an outstanding platform for training the next generation of scientists on highly complex biological questions relating to the cell cycle.