Sterol interactions influence the function of Wsc sensors

Area of Science:

• Cell Biology
• Biochemistry
• Microbiology

Background:

• Wsc1, Wsc2, and Wsc3 are crucial cell surface sensors.
• These proteins activate the cell wall integrity pathway (CWIP) upon cell wall stress.

Purpose of the Study:

• To investigate the role of sterols in Wsc protein function.
• To determine if cholesterol can substitute for ergosterol in Wsc-mediated signaling.

Main Methods:

• Genetic manipulation of sterol biosynthesis in *K. phaffii*.
• Analysis of Slt2 phosphorylation and cell wall biosynthesis.
• Protein localization studies using fluorescence microscopy.
• Site-directed mutagenesis of Wsc proteins.
• Biochemical assays with photoreactive sterol derivatives.

Main Results:

• In situ cholesterol production caused Slt2 hyper-phosphorylation and upregulated cell wall biosynthesis.
• Deletion of Wsc genes reversed these cholesterol-induced phenotypes.
• Cholesterol interacted with CRAC sterol-binding motifs in Wsc transmembrane domains.
• Mutations in CRAC motifs disrupted sterol binding.
• Similar cholesterol interactions were observed with mammalian integrins.

Conclusions:

• Wsc sensor function is dependent on specific ergosterol binding.
• Cholesterol cannot effectively substitute for ergosterol in Wsc signaling.
• CRAC motifs in transmembrane domains are critical for sterol interaction and Wsc function.