Cytoskeletal Signaling: Is Memory Encoded in Microtubule Lattices by CaMKII Phosphorylation?

• DOI: 10.1371/journal.pcbi.1002421
• Publication Date: 2012-03-08T21:55:27Z
• Authors: Travis J. A. Crad...; Jack A. Tuszynski; Stuart Hameroff
• Keywords: Signaling proteins

Memory is attributed to strengthened synaptic connections among particular brain neurons, yet membrane components are transient, whereas memories can endure. This suggests information encoded and 'hard-wired' elsewhere, e.g. at molecular levels within the post-synaptic neuron. In long-term potentiation (LTP), a cellular model for memory, calcium ion (Ca2+) flux activates hexagonal Ca2+-calmodulin dependent kinase II (CaMKII), dodacameric holoenzyme containing 2 sets of 6 domains. Each domain either phosphorylate substrate proteins, or not (i.e. encoding one bit). Thus each set extended CaMKII kinases potentially encode Ca2+ via phosphorylation as ordered arrays binary 'bits'. Candidate sites phosphorylation-encoded memory include microtubules (MTs), cylindrical organelles whose surfaces represent regular lattice with pattern polymers protein tubulin. Using mechanics modeling electrostatic profiling, we find that spatial dimensions geometry domains precisely match those MT lattices. six neighborhoods collectively, conveying "bits", thus "bytes", 64 5,281 possible bit states per CaMKII-MT byte. Signaling in MTs other cytoskeletal structures offer rapid, robust solid-state processing which may reflect general code MT-based neurons eukaryotic cells.