Protein Receptor Recognizes Gram-Negative Bacteria

The researchers, from Massachusetts General Hospital (Boston, USA), found that inactivating a protein receptor called PGRP-LC destroyed the ability of macrophages to recognize and ingest E coli bacteria but not another type of bacteria called S aureus.

This suggests the protein is critical to the macrophage's specific response against gram-negative bacteria. The study appeared March 24, 2002, on the Internet as an advanced online publication of the journal Nature. It will be published in a future print edition of the journal.

In the current study, researchers studied macrophages from the fruit fly Drosophila. "The basic templates of how organisms protect themselves against infection go back millions of years in evolution, so we can learn lessons from flies that apply to humans,” says Dr. R. Alan Ezekowitz, the study's senior author. "In this study we look at a very ancient but very important process: how bacteria are recognized and eaten by immune cells called phagocytes (a group that includes macrophages).”

Using a new method of turning off specific genes, Dr. Ezekowitz's team identified 34 macrophage proteins that are essential to the process of phagocytosis. One of these proteins is a cell surface receptor called PGRP-LC. A group of Drosophila with a mutated version of PGRP-LC was found to be much more susceptible to E coli infection than were normal fruit flies.

"PGRP-LC represents a new class of recognition molecules, and there are very similar genes in humans,” Ezekowitz says. "The next question to ask is whether this protein plays a related role in humans. Understanding the role these proteins play could eventually lead to new ways of fighting infection and to helping us figure out why some people are more susceptible to specific infections.”




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