Our team in the Surgical Neurology Branch currently focuses on discovering the functions and interrelationships among proteins mutated in familial Parkinson’s disease and ALS. This has led us to explore the molecular mechanisms of autophagy, mitochondrial dynamics, apoptosis and mitochondrial quality control.
Using biochemical, cell biological and animal studies we have found that the products of two genes mutated in autosomal recessive forms of Parkinson’s disease, PINK1 and Parkin, normally work together in the same pathway to govern mitochondrial quality control, bolstering previous evidence that mitochondrial damage is involved in Parkinson’s disease. PINK1 is a kinase located on mitochondria, and Parkin is an E3 ubiquitin ligase normally located in the cytosol. When mitochondria are damaged, PINK1 accumulates on the outer mitochondrial membrane where it phosphorylates ubiquitin chains. These phosphorylated ubiquitin chains on the outer mitochondrial membrane bind to cytosolic Parkin and activate Parkin’s E3 ubiquitin ligase activity yielding a feedback amplification loop that drives mitophagy to completion. These finding reveal a cell biology pathway where Pink1 function is paired with that of Parkin supporting the model that mutations that inactivate this quality control pathway leads to parkinsonism.
Downstream of PINK1/Parkin the machinery that mediates autophagosome recognition of damaged mitochondria links this pathway to genes mutated in ALS. Using CRISPR/Cas9 to knock out a series of autophagy receptors reveals their function and hierarchy in autophagosome engulfment of mitochondria. For example, Optineurin and NDP52 bind to ubiquitin chains on mitochondria and also recruit autophagy machinery proteins, including the upstream kinase Ulk1 and the downstream autophagosome marker, LC3, to induce autophagosome engulfment of the damaged mitochondria. Animal models that display mitochondrial damage require endogenous Parkin to prevent domaminergic neuron loss and movement disorders. Interestingly, in a murine model of mitochondrial damage, the product of the kinase PINK1 (phospho-S65 ubiquitin) increases several fold in the cortex, representing a biomarker of PINK1 activity. We are further examining biomarkers of
PINK1/Parkin activity in vivo to define roles of mitochondrial quality control in a series of physiological and pathological states.
- Richard J. Youle, Ph.D., Senior Investigator
- Chunxin Wang, Ph.D., Staff Scientist
- Peng Peng Zhu, Ph.D., Staff Scientist
- Jonathon Burman, Ph.D., Research Fellow
- Changhwan Jang, Ph.D., Postdoctoral Visiting Fellow
- Catherine Nezich, Ph.D., Postdoctoral Fellow
- Shireen Saraf, Ph.D., Postdoctoral Fellow
- Sarah Pickles, Ph.D., Postdoctoral Fellow
- Alicia Pickrell, Ph.D., Postdoctoral Fellow
- Jeni Sideris, Ph.D., Postdoctoral Fellow
- Danielle Sliter, Ph.D., Postdoctoral Fellow
- Jobert Vargas, B.S., Ph.D. Student
- Nicholas Ader, B.S., Ph.D. Student
- Zhe Zhang, B.S., Ph.D. Student
- Lazarou M, Sliter DA, Kane LA, Sarraf SA, Wang C, Burman JL, Sideris DP, Fogel AI Youle RJ. The ubiquitin kinase PINK1 recruits autophagy receptors to induce mitophagy. Nature 524: 309-314, 2015.
- Pickrell AM, Huang CH, Kennedy SR, Ordureau A, Sideris DP, Harper JW, Youle RJ. Endogenous Parkin preserves dopaminergic substantia nigral neurons following mitochondrial DNA mutagenic stress. Neuron 87: 371-381, 2015.
- Kane LA, Lazarou M, Fogel AI, Li Y, Yamano K, Sarraf SA, Banerjee S, Youle RJ. PINK1 phosphorylates ubiquitin to activate Parkin E3 ubiquitin ligase activity. J Cell Biol. 205:143-53, 2014.
- Yamano K, Fogel, AI, Wang C, van der Bliek A, Youle RJ. Mitochondrial Rab GAPs govern autophagosome biogenesis during mitophagy. eLife 3:e01612, 2014.
- Hasson SA, Kane LA, Yamano K, Huang C-H, Sliter DA, Buehler E, Wang C, Heman-Ackah SM, Hessa T, Guha R, Martin SE, Youle RJ. Genome-wide high-content RNAi screens identify regulators of Parkin upstream of mitophagy. Nature 504:291-295, 2013.
- Lazarou M, Jin SM, Kane LA, Youle RJ. Role of PINK1 binding to the TOM complex and alternate intracellular membranes in recruitment and activation of the E3 ligase Parkin. Dev Cell. 22:320-333, 2012.
- Edlich F, Banerjee S, Suzuki M, Arnoult D, Cleland M, Wang C, Neutzner A, Tjandra N, Youle RJ. Bcl-xL retrotranslocates Bax from mitochondria into the cytosol. Cell, 145: 104-116, 2011.