Indeed, cysteine cathepsins CtsB/L have recently been identified as being essential in lysosomal degradation of α-synuclein (α-syn) that accumulates in Parkinson's disease brains [23], further supporting their important role in lysosomal proteostasis and degradation of aggregation prone proteins that accumulate in the neurodegenerative disease brains. Here, CTSB is linked to neurodegenerative disease.