Autophagy lysosomal pathway dysfunction in Parkinson's disease; evidence from human genetics

In recent years, multiple lines of evidence from human genetic and molecular studies have highlighted the importance of the autophagy lysosomal pathway (ALP) in Parkinson's disease (PD). Genes such as GBA and LRRK2, which harbor some of the most common mutations associated with PD, have essential roles in the ALP. α-synuclein, encoded by the SNCA gene, is degraded mainly by the ALP, and mutations/multiplications in SNCA may lead to impairment of chaperone mediated autophagy or other ALP functions. Numerous other PD-related genes, such as PRKN, PINK1, TMEM175, SMPD1, CTSD, CTSB and many more, have also been reported to have important roles in the ALP. Understanding the relationship between ALP impairment and PD pathogenesis may be crucial for uncovering the mechanisms underlying PD, and for the development of long-awaited neuroprotective therapies. In this review, we will discuss the data linking the ALP to PD (other, atypical forms of Parkinsonism, will not be discussed in this review). We will focus on evidence from studies on specific genes and proteins, their roles in the ALP, and the potential mechanisms underlying the involvement of these genes in PD.