ClC-7 links PIKfyve inhibition to Rab-dependent LRRK2 activity at lysosomes.

Increased activity of leucine-rich repeat kinase 2 (LRRK2) confers Parkinson's disease risk. LRRK2 dynamically localizes to lysosomal membranes in response to various stresses, yet the mechanisms by which distinct lysosomal perturbations are communicated to LRRK2 remain unclear. Here, we show that inhibition of the lysosomal lipid kinase PIKfyve promotes LRRK2 recruitment and signaling through a pathway that requires the lysosomal chloride/proton antiporter ClC-7. ClC-7 in turn controls the accumulation of multiple Rab GTPases on lysosomes. LRRK2 signaling under these conditions requires its established Rab-binding surfaces, with Rab12 contributing significantly to this response. This pathway operates independently of CASM. In contrast, lysosomal stresses that induce CASM require both Rab-binding sites on LRRK2 and GABARAP for robust LRRK2 signaling. These findings identify ClC-7-dependent lysosomal remodeling and Rab accumulation as key features linking PIKfyve inhibition to LRRK2 signaling and reveal that distinct lysosomal stresses engage different combinations of Rab and GABARAP inputs to activate LRRK2.