Reciprocal regulation of Aurora kinase A and ATIP3 in the control of metaphase spindle length

Abstract

Maintaining the integrity of the mitotic spindle in metaphase is essential to ensure normal cell division. We show here that depletion of microtubule-associated protein ATIP3 reduces metaphase spindle length. Mass spectrometry analyses identiied the microtubule minus-end depolymerizing kinesin Kif2A as an ATIP3 binding protein. We show that ATIP3 controls metaphase spindle length by interacting with Kif2A and its partner Dda3 in an Aurora kinase A-dependent manner. In the absence of ATIP3, Kif2A and Dda3 accumulate at spindle poles, which is consistent with reduced poleward microtubule lux and shortening of the spindle. ATIP3 silencing also limits Aurora A localization to the poles. Transfection of GFP-Aurora A, but not kinase-dead mutant, rescues the phenotype, indicating that ATIP3 maintains Aurora A activity on the poles to control Kif2A targeting and spindle size. Collectively, these data emphasize the pivotal role of Aurora kinase A and its mutual regulation with ATIP3 in controlling spindle length.

Mitotic poleward flux: Finding balance between microtubule dynamics and sliding

“…CENP-E at laterally attached kinetochores interacts with interpolar microtubules and slides them apart until microtubule plus-ends reach the kinetochore and become end-on attached, supporting chromosome congression and transition from lateral to end-on kinetochore-microtubule attachments dependable on each other. This may be one of the reasons why the role of microtubule poleward flux in regulation of spindle length in human cells has been controversial, with some studies showing a correlation between the reduced flux rate and spindle shortening, [90][91][92] whereas other reported unchanged spindle length. [8,93] Similar discrepancy was observed in Drosophila syncytial embryos, where flux attenuation, depending on whether it originated from reduced microtubule-sliding or decreased minus-end depolymerization, was associated with spindle shortening [94] or elongation, [9] respectively.…”

“…Because the proteins that drive or regulate microtubule flux play important roles in different cellular processes during mitosis, such as in microtubule dynamics, spindle assembly and chromosome congression, it is challenging to dissect their effect on flux from these other functions, which, although largely overlapping, may not always be fully dependable on each other. This may be one of the reasons why the role of microtubule poleward flux in regulation of spindle length in human cells has been controversial, with some studies showing a correlation between the reduced flux rate and spindle shortening, [ 90–92 ] whereas other reported unchanged spindle length. [ 8,93 ] Similar discrepancy was observed in Drosophila syncytial embryos, where flux attenuation, depending on whether it originated from reduced microtubule‐sliding or decreased minus‐end depolymerization, was associated with spindle shortening [ 94 ] or elongation, [ 9 ] respectively.…”

Microtubule-Associated Protein ATIP3, an Emerging Target for Personalized Medicine in Breast Cancer

“…A major step towards the understanding of ATIP3-associated molecular mechanisms was recently provided by a proteomic approach that aimed at identifying intracellular interacting partners of ATIP3 in breast cancer cells. Co-immunoprecipitation experiments followed by mass spectrometry led to the identification of 145 ATIP3-interacting proteins, among which, nine were related to the microtubule cytoskeleton and/or mitosis [ 51 ]. Interestingly, ATIP3 interacts with KIF2A—a microtubule depolymerizing kinesin of the KinI family—and its regulator, Dda3, via a minimal sequence of 112 amino-acids present in the central basic region of the protein.…”

“…As a consequence, ATIP3 regulates the microtubule poleward flux—a mechanism of concerted polymerization at plus ends and depolymerization at minus ends of the spindle—that takes place in metaphase to maintain a constant size of the mitotic spindle [ 52 ]. In ATIP3-depleted cells, the mitotic spindle is significantly shortened [ 51 ]. This mitotic abnormality, among others, is expected to provoke major defects in chromosome segregation and subsequent aneuploidy.…”

“…Aurora kinase A is known to localize at the spindle poles where it phosphorylates KIF2A to reduce both the amount, and the depolymerizing activity, of the kinesin at this location. Of importance, ATIP3 was shown to maintain an active pool of Aurora kinase A at the poles, as a mechanism to control KIF2A activity and mitotic spindle integrity [ 51 ] ( Figure 1 ). In an independent study conducted in renal cancer cells, ATIP3 was found to regulate the phosphorylation of KIF2C (also designated MCAK), another microtubule depolymerizing kinesin of the KinI family.…”