GTP-binding proteins in polymorphonuclear granulocytes of severely burned patients

In order to study the biochemical mechanism underlying the cellular dysfunctions of polymorphonuclear granulocytes (PMNs) from severely burned patients, we analyzed the role of GTP-binding proteins (G-proteins) in PMNs from 11 burned patients. Our data demonstrate a significant enhancement of the basal GTPase activity within unstimulated neutrophils of severely burned patients compared to cells from healthy donors. This enhancement was significant within 4 weeks after the trauma, followed by a return to control levels. The increase in GTPase activity correlated with enhanced expression of the small G-protein Ras and the regulatory Ras-GTPase activating protein (Ras-GAP) compared to that in healthy donor cells. However, expression of the Ras-related protein Rap1, which is involved in initiation of the respiratory burst, was reduced. The observed changes in G-protein activity and expression impair the signal transduction cascade as well as bacterial killing and may lead to high susceptibility toward infections and finally to septic conditions.