Activation of the epidermal growth factor receptor (EGFR) not only initiates multiple signal-transduction pathways, including the MAP kinase (MAPK) pathway, but also triggers trafficking events that relocalize receptors from the cell surface to intracellular endocytic compartments. In this paper, we demonstrate that leucine-rich repeat kinase LRRK1, which contains a MAPKKK-like kinase domain, forms a complex with activated EGFR through an interaction with Grb2. Subsequently, LRRK1 and epidermal growth factor (EGF) are internalized and co-localized in early endosomes. LRRK1 regulates EGFR transport from early to late endosomes and regulates the motility of EGF-containing early endosomes in a manner dependent on its kinase activity. Furthermore, LRRK1 serves as a scaffold facilitating the interaction of EGFR with the endosomal sorting complex required for transport-0 complex, thus enabling efficient sorting of EGFR to the inner vesicles of multivesicular bodies. Our findings provide the first evidence that a MAPKKK-like protein regulates the endosomal trafficking of EGFR.

Ligand-induced activation of the epidermal growth factor receptor (EGFR) initiates trafficking events that relocalize the receptors from the cell surface to intracellular endocytic compartments. We recently reported that leucine-rich repeat kinase 1 (LRRK1) is involved in the trafficking of EGFR from early to late endosomes. In this study, we demonstrate that EGFR regulates the kinase activity of LRRK1 via tyrosine phosphorylation and that this is required for proper endosomal trafficking of EGFR. Phosphorylation of LRRK1 at Tyr-944 results in reduced LRRK1 kinase activity. Mutation of LRRK1 Tyr-944 (Y944F) abolishes EGF-stimulated tyrosine phosphorylation, resulting in hyperactivation of LRRK1 kinase activity and enhanced motility of EGF-containing endosomes toward the perinuclear region. The compartments in which EGFR accumulates are mixed endosomes and are defective in the proper formation of intraluminal vesicles of multivesicular bodies. These results suggest that feedback down-regulation of LRRK1 kinase activity by EGFR plays an important role in the appropriate endosomal trafficking of EGFR.

Proper control of epidermal growth factor receptor (EGFR) signaling is important for maintaining cellular homeostasis. Given that EGFR signaling occurs at the plasma membrane and endosomes following internalization, endosomal trafficking of EGFR spatiotemporally regulates EGFR signaling. In this process, leucine-rich repeat kinase 1 (LRRK1) has multiple roles in kinase activity-dependent transport of EGFR-containing endosomes and kinase-independent sorting of EGFR into the intraluminal vesicles (ILVs) of multivesicular bodies. Active, phosphorylated EGFR inactivates the LRRK1 kinase activity by phosphorylating Y944. In this study, we demonstrate that LRRK1 facilitates EGFR dephosphorylation by PTP1B (also known as PTPN1), an endoplasmic reticulum (ER)-localized protein tyrosine phosphatase, at the ER-endosome contact site, after which EGFR is sorted into the ILVs of endosomes. LRRK1 is required for the PTP1B-EGFR interaction in response to EGF stimulation, resulting in the downregulation of EGFR signaling. Furthermore, PTP1B activates LRRK1 by dephosphorylating pY944 on the contact site, which promotes the transport of EGFR-containing endosomes to the perinuclear region. These findings provide evidence that the ER-endosome contact site functions as a hub for LRRK1-dependent signaling that regulates EGFR trafficking.