Endosomal type Iγ PIP 5-kinase controls EGF receptor lysosomal sorting

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Endosomal trafficking and degradation of epidermal growth factor receptor (EGFR) are critical for regulating its signaling.
• Phosphatidylinositol-4,5-bisphosphate (PtdIns4,5P(2)) and phosphatidylinositol-3-phosphate (PtdIns3P) are known regulators of endocytosis and endosomal trafficking, respectively.

Purpose of the Study:

• To investigate the role of type I gamma phosphatidylinositol phosphate 5-kinase i5 (PIPKIγi5) in the endosomal sorting and degradation of EGFR.
• To elucidate the molecular mechanism by which PIPKIγi5 controls EGFR signaling.

Main Methods:

• Investigated the interaction between PIPKIγi5 and sorting nexin 5 (SNX5) in endosomal trafficking.
• Utilized loss-of-function approaches to assess the impact of PIPKIγi5 and SNX5 on EGFR sorting into intraluminal vesicles (ILVs).
• Examined the effect of impaired ILV sorting on EGFR signaling duration and intensity.
• Assessed the role of PIPKIγi5 and SNX5 in regulating Hrs ubiquitination and its association with EGFR.

Main Results:

• PIPKIγi5, an enzyme synthesizing PtdIns4,5P(2), directly controls the endosome-to-lysosome sorting of EGFR.
• PIPKIγi5 interacts with SNX5, and both proteins are essential for the proper sorting of EGFR into ILVs.
• Loss of PIPKIγi5 or SNX5 function blocks EGFR ILV sorting, leading to enhanced and prolonged EGFR signaling.
• PIPKIγi5 and SNX5 prevent Hrs ubiquitination, facilitating Hrs-EGFR association required for ILV sorting.

Conclusions:

• PIPKIγi5 and SNX5 form a critical signaling nexus regulating EGFR endosomal sorting and degradation.
• This pathway is essential for terminating EGFR signaling and preventing aberrant signaling.
• The findings reveal a novel mechanism controlling EGFR signaling through phosphoinositide metabolism and protein-protein interactions.