The Cdc42 effectors Gic1 and Gic2 regulate polarized post-Golgi secretion

Area of Science:

• Cell Biology
• Molecular Biology

Background:

• Cell polarity is crucial for cellular processes, involving Cdc42 and PtdIns(4,5)P2.
• Gic1 and Gic2 proteins interact with Cdc42 and PtdIns(4,5)P2 to control cell polarity in yeast.
• The role of Gic proteins in polarized exocytosis remained unclear.

Purpose of the Study:

• To investigate the role of Gic proteins in polarized exocytosis.
• To determine if Gic proteins regulate the exocyst complex and secretion.

Main Methods:

• Co-immunoprecipitation to assess Gic2 interaction with the exocyst complex.
• Genetic analysis using yeast mutants (e.g., gic1Δgic2Δ, sec3ΔN).
• Analysis of protein localization, cell growth, and secretion efficiency.

Main Results:

• Gic2 co-immunoprecipitated with the exocyst complex, suggesting involvement in exocytosis.
• Gic1 and Gic2 are required for polarized exocytosis in sec3ΔN mutants, affecting exocyst localization, growth, and secretion.
• Gic proteins and Sec3 share Cdc42 binding sites, but Cdc42 binding disruption doesn't always impair secretion.

Conclusions:

• Gic1/2 and Sec3 function in parallel pathways to regulate polarized post-Golgi secretion.
• Regulation of secretion by Gic proteins and Sec3 is not solely dependent on Cdc42, but may also involve PtdIns(4,5)P2.
• Findings offer insights into the molecular mechanisms of cell polarity establishment.