The Scripps Research Institute, La Jolla, California, USA
A biochemist considers whether protein misfolding plays a part in type II diabetes.
Much of my research is on cellular protein folding, and in particular on how protein misfolding or protein aggregation causes disease. My group has developed therapies for a spectrum of misfolding diseases, most of which are associated with neurodegeneration, such as Alzheimer’s.
But we are beginning to appreciate that therapies that affect protein folding could have a role in treating a much wider spectrum of diseases than is currently realized.
A compelling article from Gokhan Hotamisligil and his colleagues at Harvard University (U. Özcan et al. Science 313, 1137–1140; 2006) presents one example. They found that mice that are both obese and diabetic benefit from treatment with drugs that enhance protein folding.
Their experiment was motivated by observations that linked obesity and diabetic insulin resistance to stress in the endoplasmic reticulum (ER), a compartment in cells where a third of all proteins are folded.
The researchers gave their fat, diabetic mice chemicals that enhance protein folding in the ER. The effect was notable: the mice’s blood-sugar levels fell, they showed increased glucose tolerance and reduced lipid accumulation in the liver.
This suggests to me that protein misfolding may be at the heart of type II diabetes, the age-related disease for which these mice are a model.
Folding of the insulin receptor is inefficient. So it seems reasonable to speculate that cells could become insulin-resistant because of compromised insulin-receptor folding in the ER.
We may find, as we develop more selective small molecules to enhance ER folding, that we discover other disorders that can be treated in this way.