Mushroom bodies tiny regulates Sidekick localization to tricellular adherens junctions

Area of Science:

• Cell biology
• Developmental biology
• Neuroscience

Background:

• Sidekick is a cell adhesion molecule crucial for tricellular adherens junctions in epithelia.
• It also localizes to specific synaptic layers in Drosophila optic lobes.

Purpose of the Study:

• To investigate the functional domains of Sidekick and its interacting partners.
• To elucidate the role of Mushroom bodies tiny (a PAK4 homologue) in Sidekick localization and function.

Main Methods:

• Site-directed mutagenesis of endogenous Sidekick.
• Analysis of Sidekick localization and function in Drosophila epithelia and optic lobes.
• Investigating the interaction between Sidekick and Mushroom bodies tiny.

Main Results:

• The fifth and sixth immunoglobulin domains of Sidekick are essential for its enrichment at tricellular junctions and cell rearrangement.
• The C-terminal PDZ-binding motif is critical for localizing Sidekick and Canoe to tricellular adherens junctions.
• Mushroom bodies tiny kinase activity is required for Sidekick accumulation at tricellular junctions, while its over-activity causes mislocalization.

Conclusions:

• Sidekick's function in cell adhesion and junction formation is regulated by specific domains and interacting proteins.
• A PAK4 family member, Mushroom bodies tiny, plays a vital role in establishing specialized tricellular adherens junction structures.