A new 'bent' on fusion( MADISON Success in soccer sometimes co...)

MADISON Success in soccer sometimes comes with "bending it like Beckham." Success in cellular fusion as occurs at the moment of conception and when nerve cells exchange neurotransmitters requires that a membrane be bent before the merging process can begin, University of Wisconsin-Madison researchers have shown.

The scientists offer the first concrete evidence that a protein called synaptotagmin plays a critical role in initiating fusion by bending a section of a target membrane. The protruding dimple provides a small point of contact that can fuse with another membrane with less effort.

The finding, reported in the current issue (Aug. 21) of Cell, answers important questions relating to one of the most fundamental processes in biology.

"Fusion occurs when a sperm and an egg combine to make a person and when a virus such as HIV invades an immune cell," says senior author Edwin R. Chapman, a Howard Hughes Medical Institute professor in the physiology department at the UW-Madison School of Medicine and Public Health.

Fusion also takes place when cells deliver molecules onto their surfaces or exchange them with each other, as occurs during the transmission of messages between neurons at specialized structures called synapses. And fusion is the same process that lets the dozens of compartments working within cells transfer their contents to one another.

The process typically begins when a vesicle, or bubble-like container, buds off a donor compartment and travels to an "accepting" compartment.

"Fusion is an elementary issue that biologists have pondered for a long time," says Chapman, a synaptotagmin expert who has contributed significantly to understanding the protein's role in fusion during nerve cell communication. "It's something I've been thinking about since 1992."

A study by one group of scientists led to the theory that synaptotagmin bends the target membrane to begin fusion, but the
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