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Statistical laws of protein motion in neuronal dendritic trees

Tatjana Tchumatchenko, Max Planck Institute for Brain Research
Tuesday October 13, 12-1pm
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Abstract:聽Neurons distribute across their dendritic trees thousands of different protein species, which are necessary for maintaining synaptic function and plasticity. Given that most synaptic proteins are short-lived (half-life of 5 - 7 days), they need to be continuously produced in the soma or dendrites and trafficked to their final destination. Each dendritic branch point is a trafficking bottleneck because it splits the protein flow. The more branch points proteins meet on their journey, the lower the total protein number downstream and, as a result, the more proteins a neuron needs to produce to maintain a minimal protein number at distal synapses. Combining in vitro experiments and a novel computational framework we show here that proteins that diffuse within the cell plasma membrane have an advantage for reaching distal sites compared to proteins that diffuse in the cytoplasm. Our experiments and theory demonstrate that surface diffusion is on average 35\% more effective than cytoplasmic diffusion in providing proteins to downstream locations. This advantage emerges from a bias for forward motion at branch points when proteins diffuse within the plasma membrane. Using 3-dimensional electron microscopy (3D-EM) data, we showed that pyramidal branching statistics and the diffusion lengths of common proteins fall into a region, which minimizes overall protein need.