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Calcium and calmodulin-dependent phosphorylation of a 62 kd protein induces microtubule depolymerization in sea

J H Dinsmore1, R D Sloboda

  • 1Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755.

Cell
|June 3, 1988
PubMed

Insights

Sea urchin mitotic apparatuses (MAs) contain a protein kinase that phosphorylates a 62 kd substrate. This phosphorylation triggers microtubule depolymerization during mitosis, impacting cell division.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Mitotic apparatuses (MAs) are crucial for cell division.
  • Protein phosphorylation plays a role in regulating cellular processes.
  • The specific mechanisms controlling MA stability during mitosis are not fully understood.

Purpose of the Study:

  • To investigate the role of a calcium and calmodulin-dependent protein kinase in sea urchin MAs.
  • To determine the effect of phosphorylating a specific 62 kd substrate on MA stability.
  • To explore the implications of these findings for models of mitosis.

Main Methods:

  • Isolation of sea urchin MAs in a microtubule-stabilizing buffer.
  • In vitro kinase assays to study protein phosphorylation.
  • In vivo labeling studies to confirm substrate phosphorylation in living cells.
  • Microscopy to assess MA microtubule depolymerization.

Main Results:

  • A calcium and calmodulin-dependent protein kinase was identified in isolated MAs.
  • This kinase phosphorylates a specific 62 kd endogenous substrate.
  • Phosphorylation of the 62 kd protein led to significant MA microtubule depolymerization within 10 minutes.
  • MAs without 62 kd phosphorylation remained stable for up to 30 minutes.
  • In vivo studies confirmed phosphorylation of the 62 kd protein during mitosis.

Conclusions:

  • Specific protein phosphorylation regulates sea urchin MA stability.
  • The phosphorylation of the 62 kd protein by a calcium/calmodulin-dependent kinase is linked to microtubule depolymerization.
  • This process likely plays a role in the events of anaphase during mitosis.

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