Que Lan, insect physiologist at the University of Wisconsin-Madison, and her colleagues in the entomology department are working on a new, more targeted approach to mosquito control: inhibiting their ability to metabolize cholesterol.

Cholesterol, the sticky substance that accumulates on the lining of human arteries, is an important component of cell membranes in vertebrates and invertebrates. In mosquitoes, it is vital for growth, development and egg production.

Unlike humans, mosquitoes cannot synthesize cholesterol. They must obtain it from decomposed plants they eat while in their larval stage, living in shallow waters. Plants make phytosterol, which is converted to cholesterol in the mosquito's gut.

Using the yellow fever mosquito, Aedes aegypti, Lan and her research colleagues discovered that a sterol-carrying protein, AeSCP-2, is the vehicle that transports cholesterol in mosquito cells. Cholesterol is hydrophobic. In order to transport it in a liquid medium, such as blood or cell fluids, organisms must have a way to shield it from the watery environment through which it moves. That shield is typically a carrier protein, such as SCP-2.

Lan and her colleagues reasoned that if they could block the carrier protein, it would disrupt the uptake of cholesterol by the mosquito. Screening what she calls "a small chemical library of 16,000 compounds," Lan and her team found 57 compounds that inhibited the cholesterol-binding capacity of SCP-2.

The top five most viable inhibitor compounds were then tested on mosquito larvae, producing promising results--the larvae died. The results were dose-dependent; that is, at higher concentrations, larger numbers of larvae died. Still, the concentrations were very small, Lan says, in the range of 10 part
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Contact: Que Lan
qlan@entomology.wisc.edu
608-263-7924
University of Wisconsin-Madison
10-Sep-2004