Key concepts of the <i>C. albicans</i> wall proteome.

<p>Center: TEM picture of the cell wall and its proteins (courtesy of Iuliana V. Ene and Alistair J.P. Brown, Aberdeen). (A) Domain structure of the Hyr/Iff family (adapted from <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003050#ppat.1003050-Boisrame1" target="_blank">[7]</a>). From left to right: N-terminal signal peptide; white box, conserved domain; dark grey box, Ser/Thr-rich region; light grey box, Asp/Gly-rich region; black box, GPI-anchor addition signal. (B) Wall proteins implicated in iron acquisition from host proteins. Membrane and wall-bound CFEM proteins are able to bind hemoglobin, while Als3 is the receptor for ferritin. It is unknown if there exists a receptor for transferrin. Bound hemoglobin is taken up by endocytosis, while iron from ferritin and transferrin is sequestered via the reductive iron uptake system. (C) Effect of yeast-to-hypha transition on the wall proteome with yeast-associated (top; open squares), morphotype-independent (middle; grey squares) and hypha-associated (bottom; black squares) proteins <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003050#ppat.1003050-Heilmann1" target="_blank">[2]</a>. (D) Interaction of wall proteins with the immune system. Wall-resident superoxide dismutases (Sods) detoxify reactive oxygen species (ROS) to H₂O₂, which is subsequently converted into H₂O and O₂ by catalase activity <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003050#ppat.1003050-Frohner1" target="_blank">[20]</a>. Proteins of the Hyr/Iff family confer resistance to neutrophil and phagocyte killing through an unknown mechanism <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003050#ppat.1003050-Luo1" target="_blank">[12]</a>. Possibly, like in <i>S. cerevisiae</i>, proteases situated on the cell wall process the trans-membrane signaling protein Msb2 and liberate the extracellular domain Msb2*. Msb2* is able to bind to antimicrobial peptides (AMPs) in a dose-dependent manner and confers resistance <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003050#ppat.1003050-SzafranskiSchneider1" target="_blank">[21]</a>.</p