( Like a family of petty criminals gone w...)UCSD team unmasks family of immune system invaders

Jack E. Dixon, Ph.D., Dean for Scientific Affairs and Professor of Pharmacology and Cellular and Molecular Medicine at the UCSD School of Medicine; Neal M. Alto, Ph.D., UCSD postdoctoral fellow and lead author, and their colleagues have identified a 24-member family of bacterial proteins. Called effector proteins, they are found in bacteria, including Salmonella, Shigella and pathogenic E. coli, that cause gastrointestinal diseases. The researchers' findings will be published in the January 13, 2006 edition of the journal Cell.

These proteins help bacteria do their job of infecting the host by warding off the body's immune system. The UCSD researchers discovered how the effector proteins are able to "hijack" the body's communication network, findings that could lead novel ways to fight bacterial disease.

"While discovery of this family of effector proteins was surprising, finding the mechanisms that these proteins use to attack human cells was even more exciting," said Alto.

When pathogenic bacteria are ingested into the body ?as they generally are in diseases caused by E-coli or Salmonella commonly known as "food poisoning" ? the bacteria use a syringe-like system to "inject" their mammalian host with bacterial proteins. Once inside the host, these protein hijackers re-direct the cells communication network. The protein hijackers allow the bacteria to persist and take up nutrients, and they also shut down the immune response.

"These proteins mimic known host proteins in the cell in a very interesting way," said Dixon. "They are functional mimics that work in the same way as proteins of the host cell, b
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Source:University of California - San Diego