"The reason such a remarkable number of diseases are relevant to this set of proteins is that these proteins are at the heart of how brain cells function," explains Professor Seth Grant, Director of the Genes to Cognition Programme at the Wellcome Trust Sanger Institute.
Rather than taking traditional methods for studying just one protein at a time, the researchers developed a method that finds whole sets of proteins that bind to each other and form microscopic molecular machines. They were hunting for the 'engine room' of nerve cells, which is known to be inside the connections between nerve cells called synapses.
Synapses join the billions of nerve cells together in the brain and they are the location where learning and memory and many other behaviours are controlled.
"We developed a new method, which led to this discovery," says Dr Jyoti Choudhary, leader of the Proteomic Mass Spectrometry team, which collaborated with Professor Grant's team on the study, "and it should be equally useful in finding the basis of many other diseases in other cells and tissues of the body."
To find this key set of proteins - called MASCs (a scientific acronym for MAGUK Associated Signaling Complexes and pronounced 'mask') - the researchers adapted a method that had previously been used in yeast cells.
The method involved making a 'molecular hook' and attaching it to one protein inside brain cells of mice. They then caught the hook and pulled it out and found it brought along another 100 proteins. The set contained dozens of disease causing proteins.
"This points to the new concept that the molecular machines are defective in the diseases and that they present new ways to approach therapy," says Dr Choudhary.
Not only were there many disease proteins within the molecular machines but also proteins that control the communication between nerve cells and the mechanisms of learning and memory.
"This research is an important convergence of basic and clinical science," says Professor Grant. "Our findings are exciting because they suggest that the molecular machine itself is at the root of many important brain diseases. This was a blue-skies research project seeking the basic mechanisms of learning and memory and it has led us into some of the inner workings of the brain."
"This is a key step toward new ways to fight mental illness."