Oropharyngeal candidiasis, or thrush, is a frequent disease among immunocompromised patients as well as in elderly people and young children. Overgrowth of Candida albicans in the oral cavity is caused by decreases in saliva or reduction in mucosal antifungal peptides such as human -defensins (hBDs). Histatins are a family of histidine-rich cationic proteins secreted by major salivary glands that contribute significantly to the antifungal activity of saliva. Histatin 5 (Hst 5) has the highest fungicidal activity of the family, and kills yeast by causing selective release of intracellular ions and nucleotides from C. albicans. HBDs share some similarities in fungicidal pathways with Hst 5, but their precise mechanism of toxicity is not known. Cytotoxicity of Hst 5 is initiated by binding to the cell wall followed by cytosolic transport where it disrupts intracellular ion tranport and causes hyperosmotic stress. We have identified cell wall localized C. albicans Ssa2 proteins that are chaperone proteins assisting intracelluar transport, but the molecular identity of the transport mechanism is not known. Our preliminary data show that permeases and endocytosis are involved in peptide translocation. A significant barrier to delivery of Hst 5 or other related cationic peptides is disruption of initial binding of Hst 5 to the yeast cell wall surface by extracellular salts. Objectives of this proposal are design of salt-insensitive peptides which are efficiently transported into the cell as a basis for development of peptide- based therapeutic agents for candidiasis. Therefore, our aims are to identify minimal domains of Hst 5 that function under high salt conditions, enhance their salt resistance with helix-capping motifs, and verify that they retain optimal transport properties. Microarray analyses of Hst 5 treated C. albicans cells show that osmotic stress response by Hog1 MAPKinase pathway is an important mechanism for recovery of cells from Hst 5 toxicity. Candidal cells exposed to physiological levels of antifungal peptides in the oral environment may develop resistance through activation of Hog1p. Our overall hypothesis is that defining stress response pathways and the sensors that initiate signaling will guide strategies to overcome Candidal adaptive resistance. The objectives of the proposed studies are to identify key elements required for fungal cell uptake of peptides and subsequent adaptive responses that modulate Hst 5 and hBD toxicity. This approach will support our long-range goal to develop alternative peptide- based therapies for treatment of oral candidiasis, which is currently limited to a small group of antifungal drugs.

Public Health Relevance

Immunocompromised patients as well as elderly people and young children have a high susceptibility to oropharyngeal candidiasis or oral thrush. Objectives of this proposal are to design salt-insensitive peptides that selectively target yeast cells as oral therapeutic agents for candidiasis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE010641-19
Application #
8475448
Study Section
Special Emphasis Panel (ZRG1-MOSS-K (02))
Program Officer
Rodriguez-Chavez, Isaac R
Project Start
1994-03-01
Project End
2014-05-31
Budget Start
2013-06-01
Budget End
2014-05-31
Support Year
19
Fiscal Year
2013
Total Cost
$361,645
Indirect Cost
$133,478
Name
State University of New York at Buffalo
Department
Dentistry
Type
Schools of Dentistry
DUNS #
038633251
City
Buffalo
State
NY
Country
United States
Zip Code
14260
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Tati, Swetha; Li, Rui; Puri, Sumant et al. (2014) Histatin 5-spermidine conjugates have enhanced fungicidal activity and efficacy as a topical therapeutic for oral candidiasis. Antimicrob Agents Chemother 58:756-66
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Sun, Jianing N; Li, Wansheng; Jang, Woong Sik et al. (2008) Uptake of the antifungal cationic peptide Histatin 5 by Candida albicans Ssa2p requires binding to non-conventional sites within the ATPase domain. Mol Microbiol 70:1246-60

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