The galectin LEC-5 is a novel binding partner for RAB-11

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Rab11 is an endosomal GTPase crucial for directional trafficking and apical domain formation in polarized epithelial cells.
• Understanding the molecular mechanisms regulating apical sorting is vital for cellular organization and function.

Purpose of the Study:

• To identify novel binding partners of RAB-11 involved in apical sorting.
• To elucidate the functional interaction between RAB-11 and its newly identified binding protein, LEC-5.

Main Methods:

• Yeast two-hybrid screening using C. elegans RAB-11 as bait.
• Biochemical validation of protein interactions using GST-pull down and co-immunoprecipitation assays.
• Bimolecular fluorescence complementation (BiFC) to confirm protein-protein interaction in vivo.

Main Results:

• LEC-5 was identified as a novel binding protein for RAB-11.
• LEC-5 is an ortholog of mammalian Galectin-9 and is implicated in apical cargo sorting.
• The interaction between RAB-11 and LEC-5 was confirmed through multiple biochemical and imaging techniques, with LEC-5 binding to the C-terminus of RAB-11.

Conclusions:

• RAB-11 plays a novel role in apical sorting through its interaction with LEC-5.
• This interaction extends RAB-11's known function as a master regulator of apical trafficking.
• The findings suggest RAB-11 can translate apical sorting signals into apical vesicle directionality, providing new insights into epithelial cell polarity.