When a cell makes it all the way to cytokinesis, it has already achieved greatness. DNA replication and mitosis are Big Deals, but a cell exits mitosis only to find itself in front of that final all-uphill mile of the New York City Marathon (even as a kid watching it, I thought that was so cruel). There is a lot of regulation and reorganizing that happens for a cell to correctly complete cell division and physically split into two cells, and a recent paper sorts out how membrane trafficking proteins are coordinated during the process. Cytokinesis is the final step of cell division, when the two daughter cells are physically divided. At the start of cytokinesis, a contractile ring forms around the center of the dividing cell and begins to tighten. These contractions result in a cleavage furrow forming and pinching the dividing cell, after which only an intercellular bridge connects the two new daughter cells. With all of this contracting and pinching of the plasma membrane, it is no surprise that membrane trafficking proteins are important during cytokinesis. A recent paper looks at how endocytosis and membrane trafficking pathways are coordinated during cytokinesis. Specifically, Chesneau and colleagues found that Rab35 GTPase, an endocytic protein known to also be important in cytokinesis, is negatively regulated by ARF GTPase. ARF mutants (ones that are stuck in the activated GTP state, for those paying attention) have cytokinesis defects similar to Rab35 mutants (stuck in the inactive GDP state), including a failure after cleavage furrow progression and an instability of intercellular bridges. A seen in the images above, both the ARF mutant (bottom) and Rab35 mutant (middle) mislocalize a protein called SEPTIN2 (green, arrowheads), which is a cytoskeletal element that provides structure during cytokinesis. In a normal cell (top), SEPTIN2 is localized at the cleavage furrow.
Chesneau, L., Dambournet, D., Machicoane, M., Kouranti, I., Fukuda, M., Goud, B., & Echard, A. (2012). An ARF6/Rab35 GTPase Cascade for Endocytic Recycling and Successful Cytokinesis Current Biology DOI: 10.1016/j.cub.2011.11.058Copyright ©2011 Elsevier Ltd. All rights reserved.
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