Browsing by Author "Hu, Ke"

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    An ensemble of specifically targeted proteins stabilizes cortical microtubules in the human parasite Toxoplasma gondii
    (American Society for Cell Biology, 2016-02-01) Liu, Jun; He, Yudou; Benmerzouga, Imaan; Sullivan, William J., Jr.; Morrissette, Naomi S.; Murray, John M.; Hu, Ke; Department of Pharmacology and Toxicology, IU School of Medicine
    Although all microtubules within a single cell are polymerized from virtually identical subunits, different microtubule populations carry out specialized and diverse functions, including directional transport, force generation, and cellular morphogenesis. Functional differentiation requires specific targeting of associated proteins to subsets or even subregions of these polymers. The cytoskeleton of Toxoplasma gondii, an important human parasite, contains at least five distinct tubulin-based structures. In this work, we define the differential localization of proteins along the cortical microtubules of T. gondii, established during daughter biogenesis and regulated by protein expression and exchange. These proteins distinguish cortical from mitotic spindle microtubules, even though the assembly of these subsets is contemporaneous during cell division. Finally, proteins associated with cortical microtubules collectively protect the stability of the polymers with a remarkable degree of functional redundancy.
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    Spatial regulation of MCAK promotes cell polarization and focal adhesion turnover to drive robust cell migration
    (American Society for Cell Biology, 2021-04-01) Zong, Hailing; Hazelbaker, Mark; Moe, Christina; Ems-McClung, Stephanie C.; Hu, Ke; Walczak, Claire E.; Biology, School of Science
    The asymmetric distribution of microtubule (MT) dynamics in migrating cells is important for cell polarization, yet the underlying regulatory mechanisms remain underexplored. Here, we addressed this question by studying the role of the MT depolymerase, MCAK (mitotic centromere-associated kinesin), in the highly persistent migration of RPE-1 cells. MCAK knockdown leads to slowed migration and poor directional movement. Fixed and live cell imaging revealed that MCAK knockdown results in excessive membrane ruffling as well as defects in cell polarization and the maintenance of a major protrusive front. Additionally, loss of MCAK increases the lifetime of focal adhesions by decreasing their disassembly rate. These functions correlate with a spatial distribution of MCAK activity, wherein activity is higher in the trailing edge of cells compared with the leading edge. Overexpression of Rac1 has a dominant effect over MCAK activity, placing it downstream of or in a parallel pathway to MCAK function in migration. Together, our data support a model in which the polarized distribution of MCAK activity and subsequent differential regulation of MT dynamics contribute to cell polarity, centrosome positioning, and focal adhesion dynamics, which all help facilitate robust directional migration.