The invisible villain attaches to your brain cells while you're smoking. But how does the state of high invade a smoker's brain? It appears that sugar is the cause. A new research made at University of Southern California reveals the role of sugar as the hinge that opens a gate in the cell membrane and informs about the presence of nicotine.

The new research not only explains aspects related to the addiction, but could also lead to new improved drugs against epilepsy, schizophrenia and depression. The sugar's role has been detailed for the first time on mouse nicotinic acetylcholine receptor (nAChR), ion channel proteins involved in the passing of the signals between neurons. "Our studies fill a major gap in the field and set a new paradigm. Many existing theories, which do not consider sugar's role, are probably incomplete", said Lin Chen, associate professor of molecular and computational biology at USC.

It's an important issue of scientific debate just how signals are transmitted from the outside of a cell to the inside. "Some researchers had suggested that when a chemical such as nicotine binds to an ion channel protein on the cell surface, the protein starts a "conformational wave" that propagates a signal through the protein body to the cell membrane," Chen said.

Still, the molecular mechanism of such a wave in nAChR or any other protein has not been found. Chen's team proposes a simple mechanical role for sugar molecules bound to the surface of the receptor. "They serve as the link between the neurotransmitter binding site and the membrane region where the gate is located. The sugar is kind of like a hinge. It's pulling the door open and closed. Cutting the sugar chains stopped the gate's operation," said Chen.

"The researchers also found a water molecule deep in the receptor's core - significant because proteins normally are filled with hydrophobic (water repellent) matter that helps the structure hold its shape. The water molecule may enable the receptor to alter its shape in counterbalance to the bending hinge. Think of it as a lubricant." added the researcher.

"Previously studied "homologs" of nAChR - proteins that share its structure but not its signaling function - are entirely hydrophobic supporting the theory that the buried water molecule plays a functional role."