ABSTRACT
The cph1/cph1 efg1/efg1 double mutant in Candida albicans is defective in filamentous growth and is avirulent in a mouse model. We previously reported that Efg1p but not Cph1p is involved in drug resistance by negatively regulating ERG3 in C. albicans. In the current study, we have found that overexpression of CPH1 in Saccharomyces cerevisiae increases susceptibility to the antifungal drug fluconazole. Furthermore, in C. albicans, null mutation of CPH1 increased the expression of MDR1 as well as decreased susceptibility to fluconazole and voriconazole but not to amphotericin B. These findings indicate that although Efg1p and Cph1p may have the same effects on virulence, they have opposite effects on drug resistance in C. albicans.
Subject(s)
Antifungal Agents/pharmacology , Candida albicans/drug effects , Drug Resistance, Multiple, Fungal , Fluconazole/pharmacology , Fungal Proteins/metabolism , Gene Expression Regulation, Fungal , Voriconazole/pharmacology , Amphotericin B/pharmacology , Animals , Candida albicans/genetics , Candida albicans/pathogenicity , Fungal Proteins/genetics , Gene Expression , Gene Knockout Techniques , Mice , Saccharomyces cerevisiae/drug effects , Saccharomyces cerevisiae/genetics , VirulenceABSTRACT
The polysaccharides of Ganoderma lucidum (Reishi) possess immunomodulation activities; however, their mode of molecular action in regulating each cellular subset in the immune system is still not clear. Here, we investigate the function of the main polysaccharide fraction of Reishi (Reishi-F3) in B lymphocyte activation/differentiation. We find that Reishi-F3 causes mouse splenic B cell activation and differentiation to IgM-secreting plasma cells, and the process depends on Reishi-F3-mediated induction of Blimp-1, a master regulator capable of triggering the changes of a cascade of gene expression during plasmacytic differentiation. In human peripheral B lymphocytes, although Reishi-F3 fails to induce their activation, it is able to enhance antibody secretion, which is associated with Blimp-1 mRNA induction. The function of Reishi-F3 depends on the Toll-like receptors TLR4/TLR2 as neutralizing antibodies against TLR4/TLR2 block Reishi-F3-mediated induction of Blimp-1 mRNA and Ig secretion. We have shown that interaction of Reishi-F3 with TLR4/TLR2 followed by signaling through p38 MAPK is involved in the induction of Blimp-1 mRNA, whereas signaling through ERK, p38 MAPK, JNK, and IKK complex is involved in Reishi-F3-mediated Ig secretion. Furthermore, the differential mechanism of Reishi-F3 in mouse and human B cell activation is probably due to the presence of Blimp-1 regulatory site in human CD86 promoter. These results establish the signaling and molecular mechanisms of Reishi-F3 on promoting antibody secretion.
