SUMOylation of Wor1 by a novel SUMO E3 ligase controls cell fate in Candida albicans

Abstract

SummaryCandida albicans is the most common human fungal pathogen, yet is a normal commensal resident of the human gut. CO2 levels in the gut are much higher than in air, and it is known that elevated CO2 concentration promotes C. albicans cells to undergo a phenotypic switch from white to opaque phase. Wor1, the master regulator of opaque cell formation, is required for both the white to opaque transition and opaque maintenance. To elucidate the regulatory mechanism of Wor1, we set out to identify Wor1-interacting proteins using a yeast two-hybrid screen. A SUMO E3 ligase named Wos1 (Wor1 SUMO-ligase 1) was identified to interact with Wor1 and regulate Wor1 SUMOylation. WOS1 expression is upregulated in response to high CO2, and the induction by CO2 is dependent on the transcription factor Flo8. Under high CO2 conditions, Wos1 is required for the white to opaque switch and acts downstream of Flo8. At atmospheric CO2 levels, overexpression of Wos1 enhances Wor1 SUMOylation and promotes the white to opaque switch. Wor1 is found to be SUMOylated at lysine 385, and loss of this mark by point mutation leads to a defect in CO2-mediated opaque cell induction. Together, our genetic and biological data show that Wos1-mediated Wor1 SUMOylation contributes to the regulation of CO2-induced white to opaque switching as well as heritable maintenance of the opaque cell type.

Mms21: A Putative SUMO E3 Ligase in Candida albicans That Negatively Regulates Invasiveness and Filamentation, and Is Required for the Genotoxic and Cellular Stress Response

“…Defects in the cell division, DNA damage, and stress response machinery have been implicated in increased polarized growth and white-opaque switching Alby and Bennett 2009). Wos1, a newly characterized SUMO E3 ligase in C. albicans, affects white-opaque switching through sumoylation of Wor1 (Yan et al 2015). As Mms21 is an essential part of the Smc5/6 complex in S. cerevisiae, where this complex is critical for DNA replication checkpoints and damage repair, we explored the roles of Mms21 in C. albicans physiology to shed some light on the process the yeast-filamentous switching control, and to investigate the importance of Mms21 in response to different genotoxic and cellular stresses.…”

SUMOylation in Human Pathogenic Fungi: Role in Physiology and Virulence

“…Two of the identified SUMOylation targets were heat shock proteins Hsp60 and Hsp104, and mutations of the consensus SUMOylation residue lysine in Hsp60 and Hsp104 proteins mirrored the morphology defect and thermal stress sensitivity, respectively, of the smt3Δ/smt3Δ mutant, underscoring the role of SUMOylation in the cellular functions of Hsp60 and Hsp104 [11]. Moreover, SUMOylation of the major transcriptional factor of white-opaque phenotypic switching, CaWor1, is regulated by the SUMO E3 ligase CaWos1 (Wor1 SUMO ligase 1), and the loss of CaWor1 SUMOylation led to impaired white to opaque switching and a less stable opaque phase phenotype [91]. CaWos1 was also implicated in the cellular carbon dioxide (CO2)-sensing response, as elevated CO2 concentration led to the upregulation of the CaWOS1 gene in a Flo8-dependent manner, and deletion of CaWOS1 caused significant decrease in the white to opaque switching frequency under high CO2 conditions [91].…”

“…[90]. Over the past decade, SUMOylation has been studied in two Candida species, C. albicans and C. glabrata, and its role in Candida pathogenesis is beginning to be appreciated [11,13,91,92].…”

“…These data suggest that CaUlp1 and CaUlp3 may be the major proteases for CaSmt3 under normal growth conditions. In addition, the E2-conjugating enzyme CaUbc9 has been shown to physically interact with the SUMO E3 ligase CaWos1 [91].…”

“…Moreover, SUMOylation of the major transcriptional factor of white-opaque phenotypic switching, CaWor1, is regulated by the SUMO E3 ligase CaWos1 (Wor1 SUMO ligase 1), and the loss of CaWor1 SUMOylation led to impaired white to opaque switching and a less stable opaque phase phenotype [91]. CaWos1 was also implicated in the cellular carbon dioxide (CO 2 )-sensing response, as elevated CO 2 concentration led to the upregulation of the CaWOS1 gene in a Flo8-dependent manner, and deletion of CaWOS1 caused significant decrease in the white to opaque switching frequency under high CO 2 conditions [91]. Contrary to the wos1∆/wos1∆ mutant, the colony morphology of the smt3∆/smt3∆ mutant was heterogeneous, consisting of equal numbers of opaque, white and wrinkled colonies, with a higher switching rate among different cell states [11,91].…”