LRRK2 delays degradative receptor trafficking by impeding late endosomal budding through decreasing Rab7 activity

Abstract

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene cause late-onset autosomal dominant Parkinson's disease (PD), and sequence variations at the LRRK2 locus are associated with increased risk for sporadic PD. LRRK2 contains both GTPase and kinase domains flanked by protein interaction motifs, and mutations associated with familial PD have been described for both catalytic domains. LRRK2 has been implicated in diverse cellular processes, and recent evidence pinpoints to an important role for LRRK2 in modulating a variety of intracellular membrane trafficking pathways. However, the underlying mechanisms are poorly understood. Here, by studying the classical, well-understood, degradative trafficking pathway of the epidermal growth factor receptor (EGFR), we show that LRRK2 regulates endocytic membrane trafficking in an Rab7-dependent manner. Mutant LRRK2 expression causes a slight delay in early-to-late endosomal trafficking, and a pronounced delay in trafficking out of late endosomes, which become aberrantly elongated into tubules. This is accompanied by a delay in EGFR degradation. The LRRK2-mediated deficits in EGFR trafficking and degradation can be reverted upon coexpression of active Rab7 and of a series of proteins involved in bridging the EGFR to Rab7 on late endosomes. Effector pulldown assays indicate that pathogenic LRRK2 decreases Rab7 activity both in cells overexpressing LRRK2, as well as in fibroblasts from pathogenic mutant LRRK2 PD patients when compared with healthy controls. Together, these findings provide novel insights into a previously unknown regulation of Rab7 activity by mutant LRRK2 which impairs membrane trafficking at very late stages of the endocytic pathway.

Leucine-Rich Repeat Kinase 1 Regulates Autophagy through Turning On TBC1D2-Dependent Rab7 Inactivation

“…In contrast to the role of LRRK1 in autophagosome biogenesis, deletion or pathogenic mutation of LRRK2 causes a defect in autophagosome maturation, as revealed by the reduced conversion of LC3-I to LC3-II during autophagy (16,18,19). This defect could be explained by disrupted Rab7 activation (22,23,54). Although the molecular mechanism by which Rab7-GTP is induced in the late endosome remains controversial (55)(56)(57), it is clear that LRRK2 binds to Rab7L1-GTP and that the defect in endolysosomal and Golgi apparatus sorting caused by pathogenic LRRK2 is rescued by constitutively active Rab7L1 (23,54).…”

“…The effective conversion of Rab7-GTP/GDP recycles Rab7-GDP to the Rab7 activation step for reuse in the autophagosome-lysosome fusions. Of note, the LRRK1 homologue LRRK2, a protein related to Parkinson's disease, is involved in autophagy (16,18,19) and Rab7 cycling (22,23,54). In contrast to the role of LRRK1 in autophagosome biogenesis, deletion or pathogenic mutation of LRRK2 causes a defect in autophagosome maturation, as revealed by the reduced conversion of LC3-I to LC3-II during autophagy (16,18,19).…”

Progressive dopaminergic alterations and mitochondrial abnormalities in LRRK2 G2019S knock-in mice

“…In LRRK2 knockout rats and mice, exocytosis is impaired from lysosome-related storage organelles are impaired in alveolar type-II epithelial cells (Herzig et al, 2011; Miklavc et al, 2014). Recent data in drosophila have shown LRRK2 mediated phosphorylation has profound effects on membrane tubulation and association, and on synaptic vesicle endocytosis (Matta et al, 2012) and LRRK2 has also been proposed to regulate endocytic membrane trafficking in an Rab7-dependent manner (Gomez-Suaga et al, 2014). The endocytic impeding effects of mutant G2019S can be rescued with LRRK2-IN-1 inhibitor in mutant drosophila (Matta et al, 2012) and acute treatment with LRRK2 inhibitors reduced the frequency of spontaneous currents, the rate of synaptic vesicle trafficking and the release of neurotransmitter from isolated synaptosomes (Cirnaru et al, 2014).…”

Autophagic Pathology and Calcium Deregulation in Neurodegeneration

“…Indeed, deregulation of endolysosomal Ca 2 + homeostasis has been proposed as a primary cause of the lysosomal-storage disorder Niemann Pick C1, where the reduced lysosomal Ca 2 + results in a block in endocytic trafficking to lysosomes [73]. Our recent work further indicates that pathogenic LRRK2 regulates the activity of Rab7, a master regulator of late endocytic membrane trafficking involved in endolysosomal and autophagosome-endolysosomal fusion events [128]. Given the recently reported links between Rab7 and TPC2 [108,129], further epistasis-type studies are warranted to determine whether LRRK2 regulates Rab7 to modulate NAADP-mediated Ca 2 + release from endolysosomal stores, or whether LRRK2 regulates NAADP-mediated Ca 2 + release which then may modulate Rab7 activity for downstream endolysosomal fusion events (Fig.…”