The glucose molecule has been suspected of being more than just a source of energy and metabolic intermediate, perhaps being involved in certain signaling pathways. Until now this has been only a hypothesis since no glucose receptors that trigger signaling have been found. Scientists from the RIKEN Brain Science Institute in Wako, Japan have now identified a molecule called BOSS as a glucose receptor, opening doors for many new questions about the role of glucose in the body.
Hirabayashi’s team was investigating an unrelated signaling pathway in the fruit fly Drosophila when they recently came across an intriguing receptor molecule known as BOSS. BOSS has been previously associated with pathways related to eye development, but very little is known about its function overall, and—tantalizingly—it contains small fragments also found in the taste receptor and a sugar transport protein.
The group decided to pursue this promising lead, and their recently published findings provide strong evidence that BOSS is a direct mediator of metabolic regulation in response to glucose levels1.
BOSS is expressed primarily in the fat body, a large deposit of adipose tissue that plays an important role in sensing nutrient levels and regulating fly metabolism—in many ways, an analog of the vertebrate liver. Hirabayashi’s team also found that BOSS signaling activity was stimulated by the presence of glucose in a dose-dependent manner in cultured cells, and observed broad evidence of metabolic dysregulation in fly larvae lacking a functional boss gene. These larvae were smaller overall, and exhibited elevated levels of circulating glucose and increased lipid consumption—much like larvae with defects in insulin signaling pathways.