Interaction of Par-6 and Crumbs complexes is essential for photoreceptor morphogenesis in Drosophila

Area of Science:

• Developmental Biology
• Cell Biology
• Molecular Biology

Background:

• Apicobasal cell polarity is vital for tissue development, particularly in Drosophila photoreceptors.
• The Crumbs (Crb) complex, including Stardust (Sdt) and Discs-lost (Dlt), is localized apically and guides morphogenesis.
• Adherens junctions (AJs) and rhabdomeres require proper cell polarity for their structure.

Purpose of the Study:

• To investigate the relationship between the Crb and Par-6/atypical protein kinase C (aPKC) complexes in Drosophila photoreceptors.
• To elucidate the molecular mechanisms underlying the interdependence of these two protein complexes.
• To understand their roles in maintaining photoreceptor apical membranes and AJs.

Main Methods:

• Immunolocalization studies to determine protein colocalization in photoreceptor stalks.
• Genetic manipulation (loss-of-function and ectopic expression) to assess the impact on protein localization.
• Co-immunoprecipitation assays to identify direct protein interactions.

Main Results:

• The Crb complex colocalizes with the Par-6/aPKC complex in the rhabdomere stalk.
• Loss of Crb complex components leads to age-dependent mislocalization of Par-6/aPKC proteins.
• Absence of Par-6/aPKC proteins causes severe mislocalization and loss of the Crb complex.
• Discs-lost (Dlt) directly binds to Par-6, establishing a molecular link between the complexes.
• Ectopic expression of the Crb intracellular domain recruits the Par-6 complex.

Conclusions:

• The Crb and Par-6/aPKC complexes exhibit mutual dependence for their localization and function.
• Direct binding between Dlt and Par-6 provides a molecular basis for this interdependence.
• The interaction of these complexes is critical for the organization and maintenance of photoreceptor apical membranes and adherens junctions.