1. PINK1-Parkin Pathway as a Damage-gated Molecular Switch
Our most recent work is focused on elucidating how a protein kinase (PINK1) controls the activity of a ubiquitin E3 ligase (Parkin) to specify cell fate decisions. Mutations in genes encoding for PINK1 and Parkin have been linked to early onset of Parkinson's disease which affects more than 1 million people in North America and more than 4 million people worldwide. In this recent paper by Zhang et al. 2014, we showed that: 1) PINK1-Parkin operates as a damaged gated molecular switch for cell fate decisions. 2) Parkin catalyzes ubiquitination of selective substrates in response to specific stress stimuli;3) Parkin is the E3 ligase for Mcl-1 and activated by PINK1 through an autocatalytic mechanism.
2. Chemical Biology of the PINK1 Kinase
We have developed a chemical genetic tool for controlling PINK1 activity in mammalian cells using an orthogonal PP1 analog inhibitor 1-NA-PP1. By engineering the gatekeeper residue Met 318 to Ala, we created an analog PINK1 kinase that is sensitive to inhibition by 1-NA-PP1. Using this tool we demonstrated that the requirement of PINK1 activity in mitophagy, mitochondrial mobility and mitochondrial fusion dynamics.
3. Bioenergetics and Mitochondrial Damage Responses
Cells sense mitochondrial stress signals in their environment through resetting the steady state level and subcellular location of PINK1. We recently showed PINK1 is an unstable protein with a half-life ~30 min. The rate of PINK1 synthesis is governed by cellular biogenetics capacity. Glucose metabolism is required for the increase of the PINK1 steady state levels and subsequent mitophagy upon mitochondrial damage. Owing to the short half-life of PINK1, we showed the PINK1-Parkin pathway is particularly sensitive to translational inhibition. The intracellular levels of ATP correlate with changes in PINK1 and likely regulate PINK1 translation.