Laminin-511 and fibronectin degradation with Candida yeast

The invasion mechanism of Candida yeast is still partly unknown. In this study, we tested the ability of different commensal Candida yeast to degrade two basement membrane and extracellular matrix proteins: laminin-511 (Lm-511) and plasma fibronectin.

Human Lm-511 was produced by an immortal keratinocyte cell line, labelled with (35)S-methionine and immunoprecipitated from the growth medium with monoclonal antibodies. Human plasma fibronectin was purified from plasma samples of blood donors. Sonicated yeast cells and concentrated yeast cell growth media were incubated with Lm-511 in different pH values and the degradation was detected by fluorography. Fibronectin degradation by yeast was visualized by sodium dodecyl-sulphate polyacrylamide gel electrophoresis.

The reduced 220 kDa fibronectin monomers were found to be degraded at pH 7.8 by 10x concentrated growth media of most strains tested and at pH 3.0 the degradation was more pronounced. Sonicated cell fractions of C. tropicalis and C. parapsilosis caused degradation of plasma fibronectin at pH 7.8. Instead, none of the tested Candida cell fractions degraded Lm-511 under these conditions.

It seems that cleavage of different laminin isoforms by Candida yeast is a laminin-specific process. The ability to cleave human plasma fibronectin is species- and pH-dependent but not hyphal-dependent and also this degradation may affect epithelial integrity.