Fig. 3.

Molecular and cellular quality control. a In healthy mitochondria (blue), unfolded proteins from the cytoplasm enter by TOM and TIM. Inside the mitochondria, Mortalin and mtHsp60 help in the folding of proteins. b In case of increased level of misfolded proteins and ROS within the mitochondria (orange), the mtUPR pathway is activated. This leads to the increase of mitochondrial chaperones expression, Mortalin and mtHsp60, which help in the refolding of misfolded and oxidised proteins. TRAP1 and Omi/HtrA2 also help to refold or degrade the misfolded proteins. c In case of major cellular dysfunction, impaired mitochondria (red) triggers apoptosis. CHCHD2 allows relocalisation of Bax, which conjointly with Bak induces release of cytochrome c. TRAP1, mtHsp60 and mortalin can stimulate cytochrome c release and Omi/HtrA2 facilitates apoptosis by binding to IAPs. Also, alpha-synuclein increases Ca2+ transfer to the mitochondria that, when overloaded, induces apoptosis. Proteins in bold are linked to PD