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English: Implication of autophagy deregulation in Parkinson's disease (PD).
There are 3 types of autophagy: macroautophagy, microautophagy and chaperone-mediated autophagy (CMA). Deregulation of both macroautophagy and CMA are implicated in the pathogenesis of PD. CMA is involved in the degradation of soluble wildtype alpha-synuclein, the major constituent of Lewy bodies. Nonetheless, once oligomerized or aggregated, alpha-synuclein is likely degraded by macroautophagy instead of CMA. Interestingly, A53T and A30P mutants of alpha-synuclein are poorly degraded by CMA, but are instead degraded by macroautophagy. Furthermore, the alpha-synuclein mutants inhibit CMA, reducing CMA-mediated degradation of alpha-synuclein and survival factor MEF2D. Concomitant with the inhibition of CMA, overexpression of alpha-synuclein mutants results in a compensatory activation of macroautophagy. Activation of macroautophagy is also evident in cells treated with neurotoxin MPP+, a well-established model for Parkinsonism, or following overexpression of GPR37, another protein that is present in Lewy bodies. Finally, recent studies reveal that macroautophagy also plays a role in the turnover of fragmented mitochondria. These observations highlight the potential involvement of the autophagic pathways in the pathogenesis of PD.