The Sur7 cytoplasmic C terminus regulates morphogenesis and stress responses in Candida albicans

Area of Science:

• Cell Biology
• Mycology
• Biochemistry

Background:

• Plasma membrane domains, specifically MCC/eisosomes, are vital for fungal cell wall morphogenesis in Candida albicans.
• This process is critical for invasive growth and host environmental stress resistance.
• Sur7, a tetraspan membrane protein, localizes to MCC/eisosomes and is essential for their function.

Purpose of the Study:

• To elucidate the functional roles of the Sur7 protein in Candida albicans.
• To investigate how different regions of Sur7 contribute to its localization and function.
• To understand Sur7's contribution to cell wall integrity and stress resistance.

Main Methods:

• Site-directed mutagenesis was employed to study the Sur7 protein.
• Deletion mutant analysis was used to assess the function of specific Sur7 regions.
• Substitution mutagenesis was performed to investigate the importance of conserved residues.

Main Results:

• The N-terminal region of Sur7, including its transmembrane domains, mediates localization to MCC/eisosomes.
• Extracellular loop 1 is important for Sur7 function, though mutations often yielded weak phenotypes.
• A specific 15-amino acid motif in extracellular loop 1 is necessary for proper membrane trafficking of Sur7.
• The C-terminal domain of Sur7 is critical for resisting cell wall stress, indicating a cytoplasmic role.
• Mutagenesis studies revealed distinct roles for the N-terminal (localization) and C-terminal (cytoplasmic function) domains of Sur7.

Conclusions:

• Sur7's N-terminal region anchors it to MCC/eisosomes, ensuring proper localization.
• Sur7's C-terminal domain plays a crucial cytoplasmic role in cell wall morphogenesis and stress resistance.
• These findings highlight Sur7 as a key regulator of fungal cell wall integrity and host-pathogen interactions in Candida albicans.