SALIVARY MUC7 ANTIMICROBIAL PEPTIDE:RIM101 RESPONSE AND MECHANISM OF ACTION.
LIS, MACIEJ MIROSLAW Principal Investigator
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DESCRIPTION (provided by applicant): Cationic antimicrobial peptides (CAMP), 12-50 residues long eptides with high content of cationic amino acids, are characterized by strong activities directed against broad range of microorganisms including pathogenic bacteria, fungi and parasites. Despite intensive research and wealth of accumulated detailed information, their modes of action are not well understood. This proposal is a part of the ongoing research on elucidation of properties and mechanisms of action of MUC7 12-mer, an antimicrobial peptide derived from the low molecular-weight salivary mucin 7. This peptide has potent antimicrobial properties against opportunistic fungal pathogen Candida albicans and cariogenic oral bacterium Streptococcus mutans. We have recently employed a global approach enabling study of many different aspects of action of antimicrobial peptides at once. In this approach altered susceptibilities to the peptide of thousands deletion mutants of yeast Saccharomyces cerevisiae were tested simultaneously. Among identified deletions conferring hypersensitivity to the peptide, many involved genes associated with the RIM101 signaling pathway, best known as a response to changes in environmental pH. In the first Specific Aim we will confirm induction of this pathway by the MUC7 peptide and investigate its role in interaction of the peptide with target cells. In the second Aim we will test a hypothesis proposing existence of two distinct mechanisms of action of the MUC7 peptide, one fungicidal and the other fungiststic, and will investigate how the RIM101 signaling relates to both. We will also expand this study to the pathogenic yeast C. albicans and calcium signaling, which we have recently identified as playing a role in defense against the MUC7 peptide, analogous to that of the RIM101 response in S. cerevisiae. In the third Aim we will extend the original fitness profiling by direct selection for S. cerevisiae deletion mutants resistant to the peptide. Public Health Relevance: Due to the declining rate of discovery of new antibiotics and antifungal agents, and spread of resistant strains of pathogens, there is urgent need for development of new classes of antimicrobial therapies. Antimicrobial peptides are a potential source of novel drugs. Results of recently completed yeast deletion screen with MUC7 peptide provide new directions for studying its mechanisms of action.