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Novel protein to help battle infection

26 September 2007

The white arrowhead indicates this 5-phosphatase enzyme (green) is present at sites of phagocytosis where actin polymerization is occurring (red).

In research that could have implications for fighting infections, Monash University scientists have discovered a protein that regulates the ability of white cells to engulf foreign particles including bacteria.

White blood cells, which include structures called macrophages, kill foreign particles that could potentially harm the body. For the body to successfully kill these cells, they must first be engulfed by the macrophages.

Professor Christina Mitchell and Dr Kristy Horan from the School of Biomedical Sciences have identified a novel protein, known as 72 kDa inositol polyphosphate 5-phosphatase (72-5ptase), that actually reduces the ability of macrophages to engulf particles.

Their findings revealed that by decreasing the cellular levels of 72-5ptase, the engulfing of particles by macrophages could actually be increased.

Macrophages play a critical part in the immune system by resolving infections and may play a role in clearing damaged or dead cells. They not only directly fight disease by swallowing up infectious organisms but also promote the growth of new healthy cells to aid in healing.

"We hope by slowing down 72-5ptase activity, we may effectively allow macrophages to more efficiently engulf and kill bacteria," Professor Mitchell said.

The 72-5ptase regulates the process by removing molecules that promote macrophages to kill and digest unwanted material.

"By altering the effectiveness of 72-5ptase, there is the potential for it to be used to enhance the fight against bacterially-infected cells. It could allow macrophages to more efficiently recognise tumour cells and therefore be more efficient about killing them off," Professor Mitchell said.

While previous research has looked at the activity of 72-5ptase, this is the first study that has investigated the function of the protein. The results have been published in the latest issue of Blood, the world's leading haematology journal.

The study was funded by the NHMRC and the ARC Centre of Excellence in Structural & Functional Microbial Genomics.