Reassessment of the effect of glucagon and nucleotides on Candida albicans germ tube formation.
The role of cyclic AMP in the process of germ tube formation in Candida albicans was investigated. The exogenous supply of the nucleotide or of agents that raise its intracellular levels stimulated germination induced by N-acetyl-D-glucosamine; glucagon showed this same stimulatory effect on yeast cell transition to the hyphal form. Compounds, included glucagon, that stimulated hyphal formation, also notably enhanced the development of hyphae. The stimulatory effect of glucagon on germination was blocked by the specific antagonist des His1 [Glu9] glucagon amide, probably indicating an interaction of the hormone with a glucagon-like receptor on the membrane of the cells. Indirect immunofluorescence experiments showed that glucagon binds to the yeast cell surface. When N-acetyl-D-glucosamine was replaced by serum as inducing agent of germination, the stimulatory effect of glucagon was substantially augmented, the resulting of germination being more than 2.5-fold greater than that attained in the presence of N-acetyl-D-glucosamine; moreover, the glucagon concentration needed for half maximal stimulatory activity with serum as inducing agent was at least 50-fold lower than with N-acetyl-D-glucosamine. Monoclonal and polyclonal anti-glucagon antibodies blocked the effect of the hormone. An interesting result observed during these experiments was the fact that a definite period of incubation of C. albicans yeast cells with N-acetyl-D-glucosamine as inducer commits them to hyphal development. When serum was used as inducer, only yeast cells evaginated during the initial incubation period evolved to the hyphal form upon further incubation in the absence of serum.
Zelada
A
A
Programa de Investigaciones Bioquímicas y Fisiológicas (CIBYF-CONICET), Facultad de Agronomía, Universidad de Buenos Aires, Argentina.
Castilla
R
R
Passeron
S
S
Cantore
M L
ML
D000117:Acetylglucosamine / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects* / Q000254:growth & development; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology*; D005934:Glucagon / Q000378:metabolism / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000494:pharmacology*
D006160:Guanosine Triphosphate; D005934:Glucagon; D000242:Cyclic AMP; D000117:Acetylglucosamine