Phospho-Bcl-xL(Ser62) influences spindle assembly and chromosome segregation during mitosis

Cell Cycle. 2014;13(8):1313-26. doi: 10.4161/cc.28293. Epub 2014 Mar 3.

Abstract

Functional analysis of a series of phosphorylation mutants reveals that Bcl-xL(Ser62Ala) influences cell entry into anaphase and mitotic exit in taxol-exposed cells compared with cells expressing wild-type Bcl-xL or a series of other phosphorylation mutants, an effect that appears to be independent of its anti-apoptotic activity. During normal mitosis progression, Bcl-xL(Ser62) is strongly phosphorylated by PLK1 and MAPK14/SAPKp38α at the prometaphase, metaphase, and the anaphase boundaries, while it is de-phosphorylated at telophase and cytokinesis. Phospho-Bcl-xL(Ser62) localizes in centrosomes with γ-tubulin and in the mitotic cytosol with some spindle-assembly checkpoint signaling components, including PLK1, BubR1, and Mad2. In taxol- and nocodazole-exposed cells, phospho-Bcl-xL(Ser62) also binds to Cdc20- Mad2-, BubR1-, and Bub3-bound complexes, while Bcl-xL(Ser62Ala) does not. Silencing Bcl-xL expression and expressing the phosphorylation mutant Bcl-xL(Ser62Ala) lead to an increased number of cells harboring mitotic spindle defects including multipolar spindle, chromosome lagging and bridging, aneuploidy with micro-, bi-, or multi-nucleated cells, and cells that fail to resolve undergo mitosis within 6 h. Together, the data indicate that during mitosis, Bcl-xL(Ser62) phosphorylation impacts on spindle assembly and chromosome segregation, influencing chromosome stability. Observations of mitotic cells harboring aneuploidy with micro-, bi-, or multi-nucleated cells, and cells that fail to resolve undergo mitosis within 6 h were also made with cells expressing the phosphorylation mutant Bcl-xL(Ser49Ala) and dual mutant Bcl-xL(Ser49/62Ala).

Keywords: Bcl-xL; MAPK14/SAPKp38α; PLK1; chromosome instability; chromosome segregation; mitosis; spindle-assembly checkpoint.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Cycle Proteins / metabolism
  • Chromosome Segregation*
  • HeLa Cells
  • Humans
  • M Phase Cell Cycle Checkpoints*
  • Microtubules / metabolism
  • Mitogen-Activated Protein Kinase 14 / metabolism
  • Mitosis*
  • Mutation
  • Nocodazole / pharmacology
  • Paclitaxel / pharmacology
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / metabolism
  • Proto-Oncogene Proteins / metabolism
  • RNA, Small Interfering / genetics
  • Serine / metabolism*
  • Signal Transduction
  • Tubulin Modulators / pharmacology
  • bcl-X Protein / genetics
  • bcl-X Protein / metabolism*

Substances

  • BCL2L1 protein, human
  • Cell Cycle Proteins
  • Proto-Oncogene Proteins
  • RNA, Small Interfering
  • Tubulin Modulators
  • bcl-X Protein
  • Serine
  • Protein-Serine-Threonine Kinases
  • polo-like kinase 1
  • Mitogen-Activated Protein Kinase 14
  • Paclitaxel
  • Nocodazole