Cell Culture

Summer time is vacation time—a chance to step away from minipreps or grant deadlines and investigate nature outside the lab. For many of us, that means a trip to the beach. But don't let those colorful umbrellas and vigilant lifeguards fool you. Every foray into nature is ultimately a battle between predator and prey. In this Cell Culture, we explore cellular and molecular mechanisms used by predators at the beach to track us down and take a bite. Whether you're tanning in Tahiti or lounging on Long Island, chances are you'll probably fall prey to at least a few mosquitoes this summer. Many of these micro-vampires happily feed on any warm-blooded animal. However, a recent study by Carey et al. (2010) suggests that Anopheles gambiae (the major transmitter of malaria) has evolved chemoreceptors specifically equipped to seek out humans. A. gambiae contains 79 genes encoding odor receptors in its olfac-tory neurons. To characterize the scents detected by these proteins, the authors engineered a mutant fruit fly lacking its endogenous odor receptors and expressed the mosquito genes in their place. Fifty of the mosquito receptors were functional and exhibited excitatory responses to an array of volatile compounds in the mutant fly. Surprisingly, more than 20 of the receptors reacted to compounds in human sweat. Three receptors were narrowly tuned and had high sensitivity to particular human scents, suggesting that they are specialist receptors evolved distinctively to locate humans. For example, the AgOr2 receptor responds with high sensitivity and high selectivity to a set of aromatic compounds that includes indole, which constitute nearly 30% of our ''human scent.'' On the other hand, AgOr5 is selectively tuned to detect diacetyl, a metabolic byproduct of bacteria on your skin that has a buttery scent. The researchers are now using this system to identify compounds that ''jam'' the mosquitoes' receptors. Hopefully, this will facilitate the development of the perfect cocktail for repelling mosquitoes and combating the spread of malaria. For beachgoers in southern California, mosquitoes may be the least of their concerns this summer. A rare species of giant purple jellyfish with 3-foot-wide domes and 30-foot-long tentacles is washing ashore on San Diego beaches. Although we think of jellyfish as having ''stingers'' like a wasp, jellyfish actually rely on ultra-fast exocytosis to unload their weapons on potential prey. Thus, the sting of a jellyfish is, in fact, more similar to neurotransmitter release at a synapse …