Analyzing the functions of Rab11-effector proteins during cell division

The regulation of actin dynamics during cell division and malignancy

Actin is the most abundant protein in almost all the eukaryotic cells. Actin amino acid sequences are highly conserved and have not changed a lot during the progress of evolution, varying by no more than 20% in the completely different species, such as humans and algae. The network of actin filaments plays a crucial role in regulating cells' cytoskeleton that needs to undergo dynamic tuning and structural changes in order for various functional processes, such as cell motility, migration, adhesion, polarity establishment, cell growth and cell division, to take place in live cells. Owing to its fundamental role in the cell, actin is a prominent regulator of cell division, a process, whose success directly depends on morphological changes of actin cytoskeleton and correct segregation of duplicated chromosomes. Disorganization of actin framework during the last stage of cell division, known as cytokinesis, can lead to multinucleation and formation of polyploidy in post-mitotic cells, eventually developing into cancer. In this review, we will cover the principles of actin regulation during cell division and discuss how the control of actin dynamics is altered during the state of malignancy.

Rab14/MACF2 complex regulates endosomal targeting during cytokinesis

Abscission is a complex cellular process that is required for mitotic division. It is well established that coordinated and localized changes in actin and microtubule dynamics are vital for cytokinetic ring formation, as well as establishment of the abscission site. Actin cytoskeleton reorganization during abscission would not be possible without the interplay between Rab11- and Rab35-containing endosomes and their effector proteins, whose roles in regulating endocytic pathways at the cleavage furrow have now been studied extensively. Here, we identified Rab14 as a novel regulator of cytokinesis. We demonstrate that depletion of Rab14 causes either cytokinesis failure or significantly prolongs division time. We show that Rab14 contributes to the efficiency of recruiting Rab11-endosomes to the thin intracellular bridge (ICB) microtubules and that Rab14 knockout leads to inhibition of actin clearance at the abscission site. Finally, we demonstrate that Rab14 binds to microtubule minus-end interacting MACF2/CAMSAP3 complex and that this binding affects targeting of endosomes to the ICB microtubules. Collectively, our data identified Rab14 and MACF2/CAMSAP3 as proteins that regulate actin depolymerization and endosome targeting during cytokinesis.

Rab GTPases and cell division

Cytokinesis is a complex cellular process that leads to a physical separation of two daughter cells. The key to a successful cytokinesis is a coordinated reorganization of cellular cytoskeleton and membrane trafficking pathways. Consequently, Rab GTPases recently emerged as major regulators of cellular division. Rabs belong to a superfamily of small monomeric GTPases that regulate a diverse array of cellular functions. Rabs in particular are well-established regulators of membrane transport and have been shown to mediate several membrane transport steps including vesicle formation, molecular motor-dependent vesicle transport and targeting of transport vesicles and organelles to their correct destinations. Significantly, several Rab GTPases also have been shown to function in regulating cell division. In this review, we discuss latest findings about the function of Rabs and polarized membrane transport during different steps of cytokinesis as well as during the final stage of cell division known as abscission.