Imaging single CaMKII holoenzymes at work by high-speed atomic force microscopy

Area of Science:

• Molecular biology
• Neuroscience
• Biophysics

Background:

• Calcium/calmodulin-dependent protein kinase II (CaMKII) is crucial for synaptic plasticity.
• CaMKII is a conserved dodecameric kinase, but its molecular dynamics remain unobserved.
• Understanding CaMKII's structural behavior is key to elucidating its role in neuronal function.

Purpose of the Study:

• To visualize the activity-dependent structural dynamics of CaMKII from different species at nanometer resolution.
• To investigate the role of CaM binding and pT286 phosphorylation in CaMKII structural changes.
• To compare the structural behavior and phosphatase sensitivity of CaMKII across species.

Main Methods:

• High-speed atomic force microscopy (HS-AFM) was employed to image CaMKII from rat, hydra, and C. elegans.
• Structural dynamics were observed in response to CaM binding and phosphorylation.
• Sensitivity to Protein Phosphatase 2A (PP2A) was assessed.

Main Results:

• CaMKII dynamic behavior was dependent on CaM binding and pT286 phosphorylation.
• Only rat CaMKIIα, with specific phosphorylation sites (pT286/pT305/pT306), exhibited kinase domain oligomerization.
• Species-specific differences in CaMKII sensitivity to PP2A were observed, with rat CaMKII being least dephosphorylated.

Conclusions:

• Mammalian CaMKIIα possesses unique structural arrangements and phosphatase tolerance compared to other species.
• These evolutionarily acquired features may underlie distinct neuronal functions in mammals.
• HS-AFM provides unprecedented insight into CaMKII molecular dynamics.