Proline-induced Germ-tube Formation in Candida albicans: Role of Proline Uptake and Nitrogen Metabolism

Abstract

Proline-induced germ-tu be formation and cell-cell aggregation in four strains of Candida albicans were completely inhibited when the pH of the medium was 5.0 or lower, whereas morphogenesis induced by N-acetylglucosamine (GlcNAc) was unaffected even at pH 4.5. The pH sensitivity of proline-induced germ-tube formation was not caused by a modulation of proline uptake, which was unchanged over the pH range 4.5-6.5. The proline uptake system was specific, constitutive and subject to ammonium repression, and only one permease was detected, with a K, of 179 p~. Cultures deprived of nitrogen in the presence of glucose were derepressed for proline uptake but the yeast-mycelial transition could not be mediated by either proline or GlcNAc. The inhibition of morphogenesis was reversed when the nitrogen starvation was relieved by the addition of ammonium ions, proline, or certain amino acids. These results indicate that the nitrogen status of the cells is critical for the morphogenesis of C. albicans.

Functional reconstitution of a purified proline permease from Candida albicans: interaction with the antifungal cispentacin

“…Amino acids other than those mentioned in the 2). These results are consistent with those of L-proline uptake in intact cells (Table 2) (Jayakumar et al, 1978(Jayakumar et al, , 1979(Jayakumar et al, , 1981Dabrowa & Howard, 1981;Holmes & Shepherd, 1987).…”

“…The purified permease demonstrated stereospecific binding and other characteristics which were consistent with earlier studies on uptake of L-proline in C. albicans cells (Dabrowa & Howard, 1981;Holmes & Shepherd, 1987;Jayakumar et al, 1978Jayakumar et al, , 1979Jayakumar et al, , 1981. However, clear proof that it is purified proline permease lies with the fact that it can also mediate L-proline translocation in a reconstituted system.…”

“…In contrast to that of L-proline transport in intact cells, only monophasic binding could be detected for purified permease (Jayakumar et al, 1978(Jayakumar et al, , 1979(Jayakumar et al, , 1981Dabrowa & Howard, 1981;Holmes & Shepherd, 1987). C. albicans cells have two transport systems for Lproline; a high-affinity system with a K , of 50-100 pM and another one of low affinity with a K , of about 1 mM.…”

“…In C. albicans, the transport of proline is mediated by an inducible system, which is rather unique, since no other amino acid transporter in yeast has so far been shown to elicit inducibility (Jayakumar et at., 1978(Jayakumar et at., , 1979(Jayakumar et at., , 1981Dabrowa & Howard, 1981 ;Holmes & Shepherd, 1987).…”

Ammonium Assimilation by Candida albicans and Other Yeasts: Evidence for Activity of Glutamate Synthase

“…Recent studies (Holmes & Shepherd, 1987, 1988 have indicated that changes in nitrogen metabolism are involved in the control of morphogenesis in Candida albicans. The ammonium assimilation enzymes have a central role in nitrogen metabolism, and the aim of this study was to compare the nature and activities of these enzymes in C. albicans and other Candida spp.…”