Prof Shahid Khan, Molecular Biology Consortium (MBC) & Lahore University (LUMS)
CaMKII in dendritic spines in silico
Friday, October 14th 2011. 10am, CS0.07
The mobility of green fluorescent protein (GFP) fusions with native and mutant constructs of the major neuronal CaMKII isoforms has been measured in single dendritic spines by photo-bleaching and photo-activation protocols. Single molecule diffusion and binding reactions were simulated within Smoldyn for discrimination of mechanistic scenarios. Photo-activation in the dendrite allowed both influx to and efflux from adjacent spines to be measured for the various GFP-CaMKII constructs. Hot spots indicating binding compartments were resolved with the aid of de-noising algorithms. We estimated binding affinities in the micro-molar range for the dominant reactions of the CaMKII isoforms with the post-synaptic membrane and the actin cytoskeleton. Consideration of diffusion dynamics and spine morphology was essential for accurate characterization of biochemical parameters and, thus, mutant phenotypes. The data and the simulations together led us to a model that advocates an important role for CaMKII self-aggregation in retaining CaMKII within dendritic spines upon stimulus overload.