Cytokinesis partitions cytoplasmic and genomic materials at the end of cell division. Failure in this process causes
polyploidy, which in turn can generate
chromosomal instability, a hallmark of many
cancers. Successful cytokinesis requires cooperative interaction between contractile ring and central spindle components, but how this cooperation is established is poorly understood. Here we show that Sticky (
Sti), the Drosophila ortholog of the contractile ring component
Citron kinase (
CIT-K), interacts directly with two
kinesins, Nebbish [the fly counterpart of human
kinesin family member 14 (KIF14)] and Pavarotti [the Drosophila ortholog of human mitotic
kinesin-like protein 1 (MKLP1)], and that in turn these
kinesins interact with each other and with another central spindle
protein, Fascetto [the fly ortholog of
protein regulator of cytokinesis 1 (PRC1)].
Sti recruits Nebbish to the cleavage furrow, and both
proteins are required for midbody formation and proper localization of Pavarotti and Fascetto. These functions require
Sti kinase activity, indicating that
Sti plays both structural and regulatory roles in midbody formation. Finally, we show that
CIT-K's role in midbody formation is conserved in human cells. Our findings indicate that
CIT-K is likely to act at the top of the midbody-formation hierarchy by connecting and regulating a molecular network of contractile ring components and
microtubule-associated proteins.