Proteins that enter the secretory pathway play important roles in virulence and pathogenesis in Candida albicans, but our understanding of the trafficking of these proteins is in its early stages. In Saccharomyces cerevisiae, dominant negative alleles of YPT1 and SEC4 interrupt secretory traffic at pre- and post-Golgi steps, respectively. We therefore used a dominant negative genetic approach to examine the intracellular trafficking of several proteins associated with virulence or azole resistance. When the dominant negative ypt1(N121I) allele of C. albicans was overexpressed, yellow-fluorescent protein (YFP) tagged forms of two plasma membrane transporters (Cdr1p and Ftr1p) and the vacuolar membrane ABC transporter Mlt1p accumulated in intracellular structures that appeared related to the ER, but localization of Cdc10p and Int1p was unaffected. When the dominant negative sec4(S28N) allele of C. albicans was overexpressed, Cdr1p and Ftr1p accumulated intracellularly, and localization of Mlt1p, Cdc10p and Int1p was unaffected. These results imply that (i) Cdr1p and Ftr1p are transported to the plasma membrane by the general secretory pathway, (ii) Mlt1p enters the secretory pathway but is diverted to the vacuole at an early post-Golgi step, and (iii) like Cdc10p, Int1p does not enter the general secretory pathway.
Bibliographical noteFunding Information:
This work was supported by grants from the Department of Veterans’ Affairs (Career Development Award to S.A.L. and Merit Review Award to B.W.) and the National Institute of Allergy and Infectious Diseases (RO1-AI47442 to B.W. and KO8-AI01712 to C.G.). Sequencing of Candida albicans was accomplished with the support of the NIDR and the Burroughs Wellcome Fund. We thank the Galar Fungail Consortium for CandidaDB, and the Stanford Genome Technology Center for the Candida albicans genome sequencing project. Sequence data for Candida albicans was obtained from the Stanford Genome Technology Center website (http://www.sequence.stanford.edu/ group/candida). We thank Vasker Bhattacherjee, Margaret Hostetter, Keith Joiner, Peter Novick and Craig Roy, Yale University, for valuable advice.
- Candida albicans
- Protein secretion
- Yellow fluorescent protein