ASK1 controls spindle orientation and positioning by phosphorylating EB1 and stabilizing astral microtubules

Abstract

Orientation and positioning of the mitotic spindle are involved in dictating cell division axis and cleavage site, and play important roles in cell fate determination and tissue morphogenesis. However, how spindle movement is controlled to achieve a defined alignment within the dividing cell is not fully understood. Here, we describe an unexpected role for apoptosis signal-regulating kinase 1 (ASK1) in regulating spindle behavior. We find that ASK1 is required for proper mitotic progression and daughter cell adhesion to the substratum. ASK1 interacts with end-binding protein 1 (EB1) and phosphorylates EB1 at serine 40, threonine 154 and threonine 206, enhancing its binding to the plus ends of astral microtubules. Consequently, astral microtubules are stabilized and therefore capable of mediating spindle interaction with the cell cortex, a requirement for spindle movement. These findings reveal a previously undiscovered function of ASK1 in cell division by regulating spindle orientation and positioning, and point to the importance of protein phosphorylation in the regulation of spindle behavior.

iASPP contributes to cortex rigidity, astral microtubule capture and mitotic spindle positioning

“…For instance, it was shown that knockdown of EB1 or the tumor suppressor APC (adenomatous polyposis coli) induces an increase in mispositioned spindle and a loss of astral microtubules 39 . ASK1 (apoptosis signal-regulating kinase 1) participates in spindle orientation and positioning, by phosphorylating EB1 and stabilizing astral microtubules 40 . Expression of the short isoform of SKAP (small kinetochore-associated protein), mutated in the EB1-binding motif, led to spindles positioned far away from the cell midzone 41 .…”

Effects of FSTL1 on the proliferation and motility of breast cancer cells and vascular endothelial cells

“…Cells were incubated with primary antibodies for two hours and then with secondary antibodies for two hours . DAPI was used for DNA staining, and coverslips were mounted in 90% glycerol . Images were captured using an Axio Observer A1 fluorescence microscope (Carl Zeiss).…”

“…15,16 DAPI was used for DNA staining, and coverslips were mounted in 90% glycerol. 17 Images were captured using an Axio Observer A1 fluorescence microscope (Carl Zeiss).…”

Alteration of cell junctions during viral infection

“…Tight junctions do not constitute a static barrier, and are highly dynamic structures whose components (eg, occludin) undergo continuous turnover . Anchoring junctions provide a mechanical connection between cells; they can be one of two types depending on their constituent cytoskeletal proteins . Desmosomes and hemidesmosomes are linked to intracellular filaments, whereas adherens junctions are linked to actin .…”

“…22 Anchoring junctions provide a mechanical connection between cells; they can be one of two types depending on their constituent cytoskeletal proteins. [23][24][25][26] Desmosomes and hemidesmosomes are linked to intracellular filaments, whereas adherens junctions are linked to actin. 27 Adherens junctions serve as anchors that connect the actin cytoskeletons of adjacent cells via cadherin.…”