Arf6 anchors Cdr2 nodes at the cell cortex to control cell size at division

Area of Science:

• Cell biology
• Molecular biology
• Genetics

Background:

• Fission yeast cells utilize a size control mechanism to prevent mitotic entry until a critical cell surface area is achieved.
• The protein kinase Cdr2 forms multiprotein nodes at the medial cell cortex, inhibiting Wee1 as part of this size control system.
• The precise mechanism of Cdr2 node anchoring to the cell cortex remains incompletely understood.

Purpose of the Study:

• To identify novel components involved in Cdr2 signaling and node anchoring.
• To elucidate the role of identified factors in fission yeast cell size control.
• To understand how Cdr2 node localization contributes to surface area sensing.

Main Methods:

• Genomic screening to identify genes affecting Cdr2 signaling.
• Analysis of Arf6 GTPase localization and function in wild-type and mutant cells.
• Microscopy to observe Cdr2 node dynamics and membrane association.

Main Results:

• The conserved GTPase Arf6 was identified as a component of Cdr2 signaling.
• Cells lacking Arf6 exhibited defects in surface area-based division, shifting to volume-based control and increased cell size.
• Arf6, in its GTP-bound state, stably localized to Cdr2 nodes, and its GEF, Syt22, was essential for this localization and proper cell division size.
• Loss of Arf6 caused Cdr2 nodes to detach from the membrane and become more dynamic, with enhanced defects when combined with other node mutants.

Conclusions:

• Arf6 acts as a regulated anchor for Cdr2 nodes at the cell cortex.
• This Arf6-mediated anchoring is crucial for the cell's ability to sense and respond to cell surface area.
• The findings reveal a novel mechanism contributing to cell size control in fission yeast.