CLONING AND CHARACTERIZATION OF CAD1 AAF1, A GENE FROM CANDIDA-ALBICANS THAT INDUCES ADHERENCE TO ENDOTHELIAL-CELLS AFTER EXPRESSION IN SACCHAROMYCES-CEREVISIAE/

Adherence to the endothelial cell lining of the vasculature is probabl y a critical step in the egress of Candida albicans from the intravasc ular compartment. To identify potential adhesins that mediate the atta chment of this organism to endothelial cells, a genomic library from C . albicans was used to transform a nonadherent strain of Saccharomyces cerevisiae. The population of transformed yeasts was enriched for hig hly adherent clones by repeated passages over endothelial cells, One c lone which exhibited a fivefold increase in endothelial cell adherence , compared with S. cerevisiae transformed with vector alone, was ident ified, This organism also flocculated. The candidal DNA fragment withi n this adherent/flocculent organism was found to contain a single 1,8- kb open reading frame, which was designated CAD1. It was found to be i dentical to AAF1. The predicted protein encoded by CAD1/AAF1 contained features suggestive of a regulatory factor. Consistent with this find ing, immunoelectron microscopy revealed that CAD1/AAF1 localized to th e cytoplasm and nucleus but not the cell wall or plasma membrane of th e transformed yeasts. Because yeasts transformed with CAD1/AAF1 both f locculated and exhibited increased endothelial cell adherence, the rel ationship between adherence and flocculation mas examined. S. cerevisi ae expressing either of two flocculation phenotypes, Flo1 or NewFlo, a dhered to endothelial cells as avidly as did yeasts expressing CAD1/AA F1. Inhibition studies revealed that the flocculation phenotype induce d by CAD1/AAF1 was similar to Flo1. Thus, CAD1/AAF1 probably Encodes a regulatory protein that stimulates endothelial cell adherence in S. c erevisiae by inducing a flocculation phenotype. Whether CAD1/AAF1 cont ributes to the adherence of C. albicans to endothelial cells remains t o be determined.