Neuroligins and neurexins
Thomas Sudhof, Stanford University
Nature, vol. 455, 16 October 2008, doi:10.1038
Although it is not part of Sudhof’s article, it has been separately suggested that the neurexin/neuroligin complex could allow quantum coherence that is proposed to arise around microtubules, and might also involve presynaptic scaffold proteins, to pass through the synaptic cleft to subsequent neurons, and thus presumably a whole neuronal assembly. This has been put forward as an alternative to Hameroff’s suggestion that coherence is transmitted across a whole neuronal assembly via gap junctions.
Neurexins and neuroligins are cell-adhesion molecules that connect the presynaptic area of one neuron with the postsynaptic area of another, mediate signalling across the synaptic cleft, and specify syanptic functions. The complex is suggested to be important in the maturation of synapses, and in specifying the properties of particular circuits. Studies suggest that neurexin and neuroligin are not, however, essential for synaptic formation, but may be for subsequent maturation and function. Synapses have high plasticity, and changes in them can alter the relative contribution of synapses in a circuit. These changes probably depend on the action of the cell adhesion molecules, neurexin and neuroligin. These molecules probably bind to one another, and interact with proteins within the neurons. Current studies suggest that they mediate signalling between presynaptic and postsynaptic areas. Neurexins come in many isoforms, and it is suggested that these could code for different interactions at the synapses.