Kinesin: Critical for Long-Term Memory Storage?

  • Published5 Sep 2012
  • Reviewed5 Sep 2012
  • Author
  • Source BrainFacts/SfN

The mechanics of long-term memory formation look more like a ballet in this animation by Sathya Puthanveettil and Valerio Rizzo from The Scripps Research Institute in Florida. Is kinesin, a motor protein that “walks” along cell skeletons for the creation of new synapses, the most important protein for memory formation? Decide for yourself as you watch this 2012 Brain Awareness Video Contest submission.

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In all vertebrate and most invertebrate animals, the brain is the center of the nervous system.
Located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell, the brain of a vertebrate is the most complex organ of its body. 

In a typical human, the cerebral cortex (the largest part of the brain) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons.

In the nervous system, a synapse is a structure that permits a neuron to pass an electrical or chemical signal to another cell (neural or otherwise)

The word "synapse" comes from "synaptein", which Sir Charles Scott Sherrington and colleagues coined from the Greek "syn-" ("together") and "haptein" ("to clasp").

Synapses are essential to neuronal function: neurons are “specialized” cells whose function is to pass signals to individual target cells, and synapses are the means by which they do so. At a synapse, the plasma membrane of the signal-passing neuron (the presynaptic neuron) comes into close opposition with the membrane of the target (postsynaptic) cell. Both the presynaptic and postsynaptic sites contain extensive arrays of molecular machinery that link the two membranes together and carry out the signaling process. Memories are postulated to be represented by vastly interconnected networks of synapses in the brain.

Researchers have demonstrated that formation of Long Term Memory in the brain coincides with enhancement in synaptic transmission and the formation of additional synapses between the presynaptic axon terminal and the postsynaptic neuron it synapses with.

This phenomenon is called synaptic plasticity and it is one of the important neurobiological foundations of learning and memory.

An essential process in synaptic plasticity is the axonal transport. Analogous to shipping goods, this process allows energetic and cellular building supplies necessary for new synapse formation, to be carried downstream  (anterogradely) by molecular motors, which then act as cargo porters and continue moving on tracks named microtubule filaments.

A protein seems to be the K (Key) player in this process…its name is…
                                                            
KINESIN

Synthesized in the cell body, members of the kinesin superfamily vary in shape but the prototypical kinesin is a heterotetramer whose motor subunits (heavy chains or KHCs) form a protein dimer that binds two light chains (KLCs).

Kinesin is a protein belonging to a class of motor proteins found in eukaryotic cells. The genomes of mammals encode more than 40 kinesin proteins, organized into at least 14 families named kinesin-1 through kinesin-14.

The heavy chain of kinesin comprises a globular head (the motor domain) connected via a short, flexible neck linker to the stalk that ends in a tail domain, which associates with the light-chains. 
The head is the signature of kinesin and it has two separate binding sites: one for the microtubule and the other for ATP. 

Kinesins transport cargos by walking unidirectionally along microtubule tracks hydrolyzing one molecule of adenosine triphosphate (ATP) at each step. 

Kinesins move along microtubule filaments at a speed of 1.2 micrometer per second. 

In neurons, the requirement of active transport is highly significant because they are highly polarized and have extensive sub-cellular domains that have unique functions. 

So, in neurons, gene products such as proteins or RNAs, and organelles such as mitochondria, are transported by kinesin transport machinery from the cell body to their sub-cellular destinations. 

Kinesin transports several gene products that are important for memory formation and here we have shown how important kinesins are for long-term memory storage. Thus we think that kinesin may be a magic bullet for treating disorders of memory and cognition.