Galectin-3-mediated adherence of Proteus mirabilis to Madin-Darby canine kidney cells

Proteus mirabilis is an important cause of urinary tract infections (UTIs) and can result in acute pyelonephritis. Proteus mirabilis expresses several , morphologically distinct, fimbrial species, and previous studies have sho wn that the nonagglutinating fimbriae (NAF) mediate bacterial adherence to a number of cell lines, including Madin-Darby canine kidney (MDCK) cells. I mmunoblot overlay analysis of the plasma membrane fraction from MDCK cells with purified NAF revealed a 34-kDa band, which has been analyzed by matrix -assisted laser desorption ionization time-of-flight mass spectrometry (MAL DI-TOF MS). Database search identified galectin-3 as a potential protein ca ndidate. Immunocytochemical assay of MDCK cells with a galectin-3-specific monoclonal antibody, anti-Mac-2, confirmed its presence on the plasma membr ane extracellular surface. Preincubation of P. mirabilis with anti-Mac-2 mo noclonal antibodies, specific for galectin-3, resulted in the inhibition of bacterial binding to MDCK cells. These data suggest a role for galectin-3, interacting with appropriately glycosylated surface receptors and P. mirab ilis fimbriae, as a mediator of bacterial adherence in vitro.