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Updated: Aug 9, 2026

Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations
Published on: September 17, 2012
In vitro fusion of endocytic vesicles is inhibited by cyclin A-cdc2 kinase
P G Woodman1, J P Adamczewski, T Hunt
1Department of Biochemistry and Molecular Biology, University of Manchester Medical School, United Kingdom.
Abstract:
Receptor-mediated endocytosis and recycling are inhibited in mitotic mammalian cells, and previous studies have shown that inhibition of endocytic vesicle fusion in vitro occurs via cyclin B-cdc2 kinase. To test for the ability of cyclin A-cdc2 kinase to inhibit endocytic vesicle fusion, we employed recombinant cyclin A proteins. Addition of cyclin A to interphase extracts activated a histone kinase and markedly reduced the efficiency of endocytic vesicle fusion. By a number of criteria, inhibition of fusion was shown to be due to the action of cyclin A, via the mitosis-specific cdc2 kinase, and not an indirect effect through cyclin B. Two-stage incubations were used to demonstrate that at least one target of cyclin A-cdc2 kinase is a cytosolic component of the fusion apparatus. Reconstitution experiments showed that this component was also modified in mitotic cytosols and was unaffected by N-ethyl maleimide treatment.
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