Ca2+ dependency of N-cadherin function probed by laser tweezer and atomic force microscopy

Area of Science:

• Neuroscience
• Biophysics
• Cell Biology

Background:

• Synaptic plasticity relies on coordinated molecular mechanisms.
• Cadherin-mediated adhesion is hypothesized to play a role in synaptic plasticity.
• Extracellular calcium ([Ca2+]e) and intracellular calcium ([Ca2+]i) levels are critical in neuronal function.

Purpose of the Study:

• To provide a biophysical basis for the role of calcium-dependent cadherin modulation in synaptic plasticity.
• To investigate how extracellular calcium ([Ca2+]e) influences N-cadherin binding.
• To determine the effect of intracellular calcium ([Ca2+]i) on cadherin-mediated adhesion.

Main Methods:

• Atomic force microscopy to characterize N-cadherin binding.
• Laser tweezer trapping of N-cadherin-coated microbeads on cultured neuronal cells.
• Manipulation of extracellular calcium ([Ca2+]e) and intracellular calcium ([Ca2+]i) levels.

Main Results:

• N-cadherin adhesive activity is regulated by extracellular calcium ([Ca2+]e) between 0.3 and 0.8 mM.
• Increased intracellular calcium ([Ca2+]i) significantly reduces cadherin-mediated adhesion.
• Inhibition of actin depolymerization suppresses the reduction in adhesion caused by increased intracellular calcium ([Ca2+]i).

Conclusions:

• N-cadherin possesses biophysical properties suitable for sensing synaptic activity via calcium.
• N-cadherin is strategically positioned to regulate synaptic adhesion.
• A decrease in extracellular calcium ([Ca2+]e) coupled with an increase in intracellular calcium ([Ca2+]i) may modulate N-cadherin adhesion at synaptic sites, coordinating synaptic plasticity.