The Pla surface protease/adhesin of Yersinia pestis mediates bacterial invasion into human endothelial cells

The plasminogen activator Pla of Yersinia pestis belongs to the omptin fami ly of enterobacterial surface proteases and is responsible for the highly e fficient invasion of the plague bacterium from the subcutaneous infection s ite into the circulation. Y. pestis has been reported to invade human epith elial cells. Here, we investigated the role of Pla in bacterial invasion in to human endothelial cells. Expression of Pla in recombinant Escherichia co li XL1(pMRK1) enhanced bacterial invasion into ECV304 cells. The invasivene ss was not affected by substitution mutation at the residues S99 or D206 th at are needed for the proteolytic activity of Pla. Pla-expressing bacteria adhered to the extracellular matrix of ECV304 cells. Only weak adhesion and poor invasion were seen with the recombinant E. coli XL1(pMRK2), which exp resses the omptin homolog from E. coli. The results identify Pla as an inva sion protein of Y. pestis and show that the invasive function does not invo lve the proteolytic activity of Pla. (C) 2001 Federation of European Bioche mical Societies. Published by Elsevier Science B.V. All rights reserved.