title: Expression levels of a kinesin-13 microtubule depolymerase modulates the effectiveness of anti-microtubule agents.
abstract: BACKGROUND
  Chemotherapeutic drugs often target the microtubule cytoskeleton as a means to disrupt cancer cell mitosis and proliferation. Anti-microtubule drugs inhibit microtubule dynamics, thereby triggering apoptosis when dividing cells activate the mitotic checkpoint. Microtubule dynamics are regulated by microtubule-associated proteins (MAPs); however, we lack a comprehensive understanding about how anti-microtubule agents functionally interact with MAPs. In this report, we test the hypothesis that the cellular levels of microtubule depolymerases, in this case kinesin-13 s, modulate the effectiveness of the microtubule disrupting drug colchicine.
  
  
  RESULTS
  We used a combination of RNA interference (RNAi), high-throughput microscopy, and time-lapse video microscopy in Drosophila S2 cells to identify a specific MAP, kinesin-like protein 10A (KLP10A), that contributes to the efficacy of the anti-microtubule drug colchicine. KLP10A is an essential microtubule depolymerase throughout the cell cycle. We find that depletion of KLP10A in S2 cells confers resistance to colchicine-induced microtubule depolymerization to a much greater extent than depletion of several other destabilizing MAPs. Using image-based assays, we determined that control cells retained 58% (+/-2%SEM) of microtubule polymer when after treatment with 2 microM colchicine for 1 hour, while cells depleted of KLP10A by RNAi retained 74% (+/-1%SEM). Likewise, overexpression of KLP10A-GFP results in increased susceptibility to microtubule depolymerization by colchicine.
  
  
  CONCLUSIONS
  Our results demonstrate that the efficacy of microtubule destabilization by a pharmacological agent is dependent upon the cellular expression of a microtubule depolymerase. These findings suggest that expression levels of Kif2A, the human kinesin-13 family member, may be an attractive biomarker to assess the effectiveness of anti-microtubule chemotherapies. Knowledge of how MAP expression levels affect the action of anti-microtubule drugs may prove useful for evaluating possible modes of cancer treatment.
authors.affiliation: Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.
authors.forename: Gregory V
authors.initials: GV
authors.lastname: Schimizzi
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Currie
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Rogers
mesh_terms: D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D017931:DNA Primers; D004330:Drosophila; D016547:Kinesins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D034622:RNA Interference
chemical_list: D017931:DNA Primers; D016547:Kinesins