Pak1 and PP2A antagonize aPKC function to support cortical tension induced by the Crumbs-Yurt complex

Area of Science:

• Cell Biology
• Developmental Biology
• Biochemistry

Background:

• The Drosophila Crumbs protein is vital for apical domain establishment and growth in epithelial cells.
• Yurt protein restricts Crumbs' effect on apical membrane growth, maintaining the apical/lateral membrane ratio essential for epithelial structures.
• Proper epithelial architecture relies on precise control of cell polarity and contractility.

Purpose of the Study:

• To investigate the role of Yurt in regulating Myosin-dependent cortical tension downstream of Crumbs.
• To elucidate the regulatory mechanisms controlling Yurt activity, specifically the roles of kinases aPKC and Pak1, and phosphatase PP2A.
• To understand how these interactions contribute to the plasticity of Crumbs function and epithelial tissue architecture.

Main Methods:

• Overexpression of Yurt in Drosophila epithelial cells.
• Analysis of apical constriction in response to Yurt modulation.
• Investigating the phosphorylation status of Yurt upon manipulation of aPKC, Pak1, and PP2A activities.

Main Results:

• Yurt overexpression induces apical constriction in epithelial cells by increasing Myosin-dependent cortical tension.
• The kinase aPKC phosphorylates Yurt, leading to its dissociation from the apical domain and release of apical tension.
• The Pak1-PP2A module dephosphorylates Yurt, opposing aPKC and promoting Yurt-induced apical constriction.

Conclusions:

• Yurt plays a dual role in regulating apical membrane growth and cortical tension.
• A complex interplay between Yurt, aPKC, Pak1, and PP2A provides functional plasticity to Crumbs.
• These findings enhance understanding of how epithelial cell polarization and contractility proteins interact to control tissue architecture.