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Differential regulation by ATP versus ADP further links CaMKII aggregation to ischemic conditions

Rebekah S Vest1, Heather O'Leary, K Ulrich Bayer

  • 1Department of Pharmacology, University of Colorado Denver, Aurora, CO 80045, United States.

FEBS Letters
|October 21, 2009
PubMed

Insights

Calcium-calmodulin-dependent protein kinase II (CaMKII) self-aggregation causes extra-synaptic clusters during ischemia. High ATP prevents this via T286 auto-phosphorylation, clarifying aggregation mechanisms.

Area of Science:

  • Neuroscience
  • Molecular Biology
  • Biochemistry

Background:

  • Calcium-calmodulin-dependent protein kinase II (CaMKII) is crucial for synaptic plasticity.
  • CaMKII forms extra-synaptic clusters under ischemic conditions, a phenomenon not fully understood.

Purpose of the Study:

  • To investigate the self-aggregation mechanism of CaMKII holoenzymes under ischemic conditions.
  • To clarify the roles of ATP, ADP, pH, and T286 auto-phosphorylation in CaMKII aggregation and extra-synaptic clustering.

Main Methods:

  • In vitro aggregation assays mimicking ischemic conditions (low pH, Ca2+, calmodulin, ATP/ADP levels).
  • Mutational analysis of CaMKII to assess the impact of T286 auto-phosphorylation and nucleotide binding.
  • Examination of extra-synaptic CaMKII clustering in neurons.

Main Results:

  • Ischemic conditions (low pH, Ca2+/calmodulin, low ATP/high ADP) promote CaMKII holoenzyme self-aggregation in vitro.
  • High ATP prevents aggregation through T286 auto-phosphorylation.
  • Nucleotide binding, but not necessarily auto-phosphorylation, is required for extra-synaptic clustering in neurons.

Conclusions:

  • CaMKII aggregation is driven by self-assembly of holoenzymes under simulated ischemic conditions.
  • The findings resolve paradoxes regarding nucleotide and phosphorylation requirements for CaMKII aggregation.
  • A mechanism involving inter-holoenzyme T286-region/T-site interaction is proposed for CaMKII aggregation and clustering.

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