Sorting nexin 27 interacts with multidrug resistance-associated protein 4 (MRP4) and mediates internalization of MRP4

Area of Science:

• Molecular Biology
• Cell Biology
• Pharmacology

Background:

• Multidrug resistance-associated protein 4 (MRP4/ABCC4) is crucial for drug and endogenous compound distribution via cellular efflux.
• The mechanisms controlling MRP4's cell surface expression remain largely uncharacterized.
• MRP4 possesses a PDZ-binding motif, suggesting potential regulation by PDZ adaptor proteins.

Purpose of the Study:

• To investigate the interaction between MRP4 and PDZ adaptor proteins.
• To elucidate the role of sorting nexin 27 (SNX27) in regulating MRP4 cell surface expression and function.

Main Methods:

• GST pull-down assays and mass spectrometry to identify interacting proteins.
• Coimmunoprecipitation and siRNA-mediated knockdown in HEK293 cells to confirm SNX27-MRP4 interaction and functional effects.
• Cell surface biotinylation and immunocytochemistry in HEK293 and COS-1 cells to assess protein localization and internalization.

Main Results:

• Sorting nexin 27 (SNX27) was identified as a PDZ adaptor protein interacting with MRP4's PDZ-binding motif.
• SNX27 knockdown increased plasma membrane MRP4 expression, enhanced substrate efflux, and conferred drug resistance.
• SNX27 promotes MRP4 endocytosis, thereby negatively regulating its surface expression and transport activity.

Conclusions:

• SNX27 directly interacts with MRP4, modulating its cell surface abundance.
• SNX27 plays a critical role in the endocytosis and regulation of MRP4.
• Understanding the SNX27-MRP4 interaction provides insights into the regulation of drug transport and cellular resistance.