Proximity Labeling Reveals How Lrp2 Interacts with the Endocytic Machine

Area of Science:

• Cell Biology
• Molecular Biology
• Nephrology

Background:

• Low-density lipoprotein-related receptor 2 (LRP2), also known as Megalin, is a scavenger receptor involved in nutrient and toxin reabsorption in the kidney.
• LRP2, along with Cubilin and Amnionless, mediates endocytosis of various ligands from glomerular filtrate.
• Emerging evidence suggests LRP2 has roles in endocytosis beyond its known ligand-binding functions.

Purpose of the Study:

• To elucidate the broader role of LRP2 in endocytosis.
• To identify LRP2's interacting partners involved in endocytic processes.
• To understand how LRP2 organizes cellular machinery at the apical membrane.

Main Methods:

• Engineered LRP2-APEX2-expressing mice for in vivo proximity-dependent biotinylation.
• Utilized mass spectrometry to identify biotinylated cytoplasmic proteins interacting with LRP2.
• Performed kidney tissue immunostaining to validate protein localization and interactions.

Main Results:

• Identified known and novel endocytic regulators interacting with LRP2.
• Demonstrated LRP2's role in organizing apical membrane proteins via PDZ domain interactions.
• Showcased LRP2's engagement with molecular motors and regulators during endocytosis.

Conclusions:

• LRP2 plays a central role in organizing the apical membrane and facilitating endocytosis.
• LRP2 interacts with a network of proteins critical for kidney reabsorption and fluid-phase endocytosis.
• These interactions are dependent on the presence of LRP2, highlighting its essential function.