Sap1 to Sap8 are secreted into the extracellular environment, whi

Sap1 to Sap8 are secreted into the extracellular environment, while Sap9 and Sap10 are retained at the cell surface via a (modified) GPI anchor (Albrecht et al., 2006). Saps are involved in multiple processes, like degradation of host tissues and proteins to facilitate invasion and

nutrient uptake. Furthermore, they can degrade host immune proteins (Gropp et al., 2009). While Sap1 to Sap3 activities are maximal at pH 3–5, Sap4 to Sap6 activities are optimal at pH 5–7, correlating with the fact that Sap4 to Sap6 are essential for systemic infections and were only present in the secretome of hypha-enriched cultures grown in the presence of GlcNAc at pH 7.4 (Felk et al., 2002; Sorgo et al., 2010). Accordingly, Sap2 and Sap3 were exclusively detected at pH 4. Also phospholipases are involved in tissue selleckchem destruction and invasion. All five phospholipase MG-132 chemical structure B genes in C. albicans contain a signal sequence for secretion, while only

PLB3, PLB4.5, and PLB5 have a putative GPI attachment signal (De Groot et al., 2003). Plb3 has been detected in fluconazole-stressed cultures but only at very low levels (Sorgo et al., 2011), probably because the correct induction conditions were not met. Of the ten lipase genes encoded by C. albicans, all except LIP7 contain an N-terminal signal for secretion. LIP genes were shown to be differentially expressed depending on the growth condition, and expression was independent of lipids (Hube et al., 2000). Nevertheless, until now only Lip4 has been identified at very low levels in exponentially growing cultures with lactate as carbon source (Ene et al., 2012). Apart from hydrolytic enzymes, C. albicans also secretes proteins to sequester metal ions. Zinc is an important trace metal required for microbial growth. Zinc uptake is facilitated by two proteins, the secreted protein Pra1 and the zinc transporter Zrt1 (Citiulo et al., 2012). Pra1 (pH-regulated antigen) is highly expressed at neutral pH and shows negligible expression at acidic pH (Sentandreu et al., 1998). Upon host cell penetration, C. albicans secretes

Pra1 into the host cell cytosol, scavenges available zinc, and re-associates with the fungal cell, where it interacts with the zinc transporter Acetophenone Zrt1 to enable zinc uptake. Interestingly, Pra1 is recognized by a leukocyte receptor protein, and this probably explains why pra1 mutant cells are more resistant to leukocyte killing and more virulent in a murine model of systemic infection (Soloviev et al., 2011). Freely available iron is also very scarce during infection, and iron is actively scavenged by C. albicans from its host. All five members of the C. albicans Rbt5 family, comprising Csa1, Csa2, Pga7, Pga10, and Rbt5, are CFEM proteins, which are characterized by the possession of one or more 8-cysteine-containing domains.

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