Candida albicans and Cryptococcus neoformans are major causes of systemic fungal infections, particularly in patients with acquired immunodeficiency syndrome. Metabolic labeling studies revealed that these organisms synthesize a small number of N-myristoylproteins, the most prominent being 20-kDa ADP- ribosylation factors (Arfs). C. albicans Arf has ~80% identity with the essential Arf1 and Arf2 proteins of Saccharomyces cerevisiae. [3H]Myristic acid analogs with oxygen for -CH2-substitutions at C4, C6, C11, and C13 are incorporated into cellular N-myristoylproteins, phospholipids, and neutral lipids produced by these three yeasts during exponential growth at 30 °C in complex media. Analog- and organism-specific differences in the efficiency of labeling of proteins and lipid classes were observed. The effects of oxatetradecanoic acids with oxygen for -CH2- substitutions at C3-C13 on C. neoformans, C. albicans, and S. cerevisiae were assessed during mid-log phase growth at 30 °C. A single dose of 3-oxa-, 4-oxa-, 5-oxa- or 6- oxatetradecanoic acid (O3-O6, final concentration = 300 μM) was able to inhibit growth of C. neoformans in the order O4 > O5 > O3 ~ O6. The other compounds were inactive. 4-Oxatetradecanoic acid was fungicidal, producing a 10,000-fold reduction in viable cell number 1 h after administration and continued suppression of cell growth for 7 h. A clear dose response was observed over a concentration range of 100-300 μM. 4-Oxatridecanoic acid was 100-fold less potent in reducing cell viability than 4-oxatetradecanoic acid but more potent than 5-oxatridecanoic acid. O4 produced ~10-100-fold reductions in the viability of C. albicans and S. cerevisiae at 300-500 μM, respectively, whereas O5 and O6 were less active. Since N-myristoylation of the Pr55(gag) polyprotein precursor produced by human immunodeficiency virus I (HIV-I) is essential for its assembly, we also assessed the antiviral effects of 4-oxatetradecanoic acid. O4 is able to produce a 50% reduction in the replication of HIV-I in acutely infected human T-lymphocyte cell lines at a concentration of 18 μM. Together, these data suggest that (i) the position of the oxygen for methylene substitution is a critical determinant of the fungicidal activity of O4 and (ii) NMT may be an attractive therapeutic target for treating opportunistic fungal infections in patients infected with HIV-I.
|Number of pages||11|
|Journal||Journal of Biological Chemistry|
|State||Published - Jan 1 1992|