The PHR Family: The Role of Extracellular Transglycosylases in Shaping Candida albicans Cells

Abstract

Candida albicans is an opportunistic microorganism that can become a pathogen causing mild superficial mycosis or more severe invasive infections that can be life-threatening for debilitated patients. In the etiology of invasive infections, key factors are the adaptability of C. albicans to the different niches of the human body and the transition from a yeast form to hypha. Hyphal morphology confers high adhesiveness to the host cells, as well as the ability to penetrate into organs. The cell wall plays a crucial role in the morphological changes C. albicans undergoes in response to specific environmental cues. Among the different categories of enzymes involved in the formation of the fungal cell wall, the GH72 family of transglycosylases plays an important assembly role. These enzymes cut and religate β-(1,3)-glucan, the major determinant of cell shape. In C. albicans, the PHR family encodes GH72 enzymes, some of which work in specific environmental conditions. In this review, we will summarize the work from the initial discovery of PHR genes to the study of the pH-dependent expression of PHR1 and PHR2, from the characterization of the gene products to the recent findings concerning the stress response generated by the lack of GH72 activity in C. albicans hyphae.

Mild Heat Stress Affects on the Cell Wall Structure in <i>Candida albicans</i> Biofilm

“…Therefore, this difference in comparison criteria for gene expression between microarray analysis and quantitative PCR method may yield differences in results. The β -glucan transglycosylase gene PHR1 31,32) was selected as a gene whose expression is suppressed at 37ºC and is promoted at 39ºC (Fig. 3(b)).…”

Special Issue: Fungal Cell Wall

“…Given the impact of these families on the cell wall and the importance of the cell wall structure in mediating host-pathogen interactions, these families are essential for virulence and in some instances even for fungus viability. The latter is observed for Gel4 in A. fumigatus [ 32 ], Gas1 and Gas2 [ 33 ], and Phr1–Phr2 in C. albicans [ 34 ].…”

The Cell Wall of Candida albicans: A Proteomics View

“…One type of proteins described as main cross linkers of cell wall components are the members of the gas family that only contains members of the fungal kingdom. C. albicans possesses five genes encoding members of this family, the PHR1, PHR2, PHR3, PGA4, and PGA5 genes [10]. These proteins are β-1,3-glucanases that also exhibit transglucosidase activity and are needed for cross linking β-1,3-glucan and β-1,6-glucan.…”

“…These proteins are β-1,3-glucanases that also exhibit transglucosidase activity and are needed for cross linking β-1,3-glucan and β-1,6-glucan. PHR1 and PHR2 genes are the only members of the family that are responsive to changes in pH [10]. PHR1 gene is able to complement the S. cerevisiae GAS1/GGP1 null mutant, which has as main phenotypic characteristics, spherical shape, and affectation of normal budding pattern in the stationary phase of growth curve, indicating that the PHR1 gene is the ortholog of GAS1/GGP1 in C. albicans [11].…”