CaM kinase II initiates meiotic spindle depolymerization independently of APC/C activation

J Cell Biol. 2008 Dec 15;183(6):1007-17. doi: 10.1083/jcb.200807006. Epub 2008 Dec 8.


Altered spindle microtubule dynamics at anaphase onset are the basis for chromosome segregation. In Xenopus laevis egg extracts, increasing free calcium levels and subsequently rising calcium-calmodulin-dependent kinase II (CaMKII) activity promote a release from meiosis II arrest and reentry into anaphase. CaMKII induces the activation of the anaphase-promoting complex/cyclosome (APC/C), which destines securin and cyclin B for degradation to allow chromosome separation and mitotic exit. In this study, we investigated the calcium-dependent signal responsible for microtubule depolymerization at anaphase onset after release from meiotic arrest in Xenopus egg extracts. Using Ran-guanosine triphosphate-mediated microtubule assemblies and quantitative analysis of complete spindles, we demonstrate that CaMKII triggers anaphase microtubule depolymerization. A CaMKII-induced twofold increase in microtubule catastrophe rates can explain reduced microtubule stability. However, calcium or constitutively active CaMKII promotes microtubule destabilization even upon APC/C inhibition and in the presence of high cyclin-dependent kinase 1 activity. Therefore, our data demonstrate that CaMKII turns on parallel pathways to activate the APC/C and to induce microtubule depolymerization at meiotic anaphase onset.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anaphase
  • Anaphase-Promoting Complex-Cyclosome
  • Animals
  • Biopolymers / metabolism*
  • CDC2 Protein Kinase / metabolism
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2 / metabolism*
  • Cell Extracts
  • Centrosome / enzymology
  • Enzyme Activation
  • Meiosis*
  • Metaphase
  • Microtubules / enzymology
  • Ovum / cytology
  • Ovum / enzymology
  • Ubiquitin-Protein Ligase Complexes / metabolism*
  • Xenopus / metabolism*


  • Biopolymers
  • Cell Extracts
  • Ubiquitin-Protein Ligase Complexes
  • Anaphase-Promoting Complex-Cyclosome
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2
  • CDC2 Protein Kinase