Analysis of the supra-molecular structure and function of the apical junctional complex

• Applicant: Professor Dr. Alf Honigmann
• Subject Area: Cell Biology ; Biophysics ; Structural Biology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 565330023

The apical junctional complex (AJC) plays a vital role in controlling tissue permeability, cell polarity, and mechanical homeostasis of epithelial tissues. This project aims to provide a link between the functions and molecular organization of the AJC in epithelial tissues. The key objectives are: Characterizing AJC Structure (WP1): Combining super-resolution STED microscopy with 3D tissue culture (MDCK cysts), we aim to map the supra-molecular organization of the AJC in mammalian epithelial cells. Using a custom image analysis and modeling pipeline we will quantify the distribution of 20-30 AJC proteins to establish how the apical domain, tight junctions (TJ) and adherens junctions (AJ) are connected and interact with the cytoskeleton. Understanding Molecular Dependency (WP2): Through genetic knockouts and perturbations, we will explore how specific TJ and AJ proteins contribute to the structural organization of the AJC. By analyzing how mutants change the AJC structure, the project will determine redundancy, robustness, and functional contributions of individual components of the AJC. Exploring Mechanical Feedback (WP3): To understand how the AJC structure is related to mechanical tension of the cell cortex, we will study how acute perturbations of AJs and TJs proteins impact junctional tension. Here, we will use laser ablation to quantify tension and we will use optogenetics to acutely increase tension and determine the response on the AJC ultrastructure level. By integrating structural analysis, genetic editing, and biophysical analyses, this project will build a comprehensive model of the AJC structure-function relation. The outcomes will illuminate the molecular basis of epithelial integrity, mechanisms of tissue mechanics, and pathways involved in diseases linked to AJC dysfunction, such as cancer and inflammatory disorders.

• DFG Programme: Research Grants