bims-tofagi 2024-05-12 papers

J Cell Biol. 2024 Jul 01. pii: e202309015. [Epub ahead of print]223(7):

A RAB7A phosphoswitch coordinates Rubicon Homology protein regulation of Parkin-dependent mitophagy.

Dan A Tudorica, Bishal Basak, Alexia S Puerta Cordova, Grace Khuu, Kevin Rose, Michael Lazarou, Erika L F Holzbaur, James H Hurley.

Activation of PINK1 and Parkin in response to mitochondrial damage initiates a response that includes phosphorylation of RAB7A at Ser72. Rubicon is a RAB7A binding negative regulator of autophagy. The structure of the Rubicon:RAB7A complex suggests that phosphorylation of RAB7A at Ser72 would block Rubicon binding. Indeed, in vitro phosphorylation of RAB7A by TBK1 abrogates Rubicon:RAB7A binding. Pacer, a positive regulator of autophagy, has an RH domain with a basic triad predicted to bind an introduced phosphate. Consistent with this, Pacer-RH binds to phosho-RAB7A but not to unphosphorylated RAB7A. In cells, mitochondrial depolarization reduces Rubicon:RAB7A colocalization whilst recruiting Pacer to phospho-RAB7A-positive puncta. Pacer knockout reduces Parkin mitophagy with little effect on bulk autophagy or Parkin-independent mitophagy. Rescue of Parkin-dependent mitophagy requires the intact pRAB7A phosphate-binding basic triad of Pacer. Together these structural and functional data support a model in which the TBK1-dependent phosphorylation of RAB7A serves as a switch, promoting mitophagy by relieving Rubicon inhibition and favoring Pacer activation.

DOI: https://doi.org/10.1083/jcb.202309015

FEBS J. 2024 May 06.

A new mutation in the Parkinson's-related FBXO7 gene impairs mitochondrial and proteasomal function.

Elisa Navarro, Noemí Esteras.

Around 10% of Parkinson's disease (PD) cases are associated with mutations in various genes, including FBXO7, which encodes the substrate-recognition component for the Skp1-Cullin-F-box (SCF) class of ubiquitin E3 ligases that target proteins for proteasomal degradation. In their recent study, Al Rawi et al. characterized a new mutation in FBXO7, L250P, in a pediatric patient. Their findings reveal that the L250P mutation abolishes Fbxo7 interaction with the proteasome regulator, proteasome inhibitor 31kD (PI31), affecting proteasomal activity and the ubiquitination of some of the ligase's targets. Furthermore, the authors show that this previously undescribed mutation impairs mitochondrial function and mitophagy, emphasizing the importance of mitochondrial and proteasomal dysfunction in PD pathogenesis.

Keywords: Fbxo7/PARK15; PI31/PSMF1; Parkinson; mitochondria; proteasome

DOI: https://doi.org/10.1111/febs.17155

RSC Chem Biol. 2024 May 08. 5(5): 439-446

Discovery of potent and selective activity-based probes (ABPs) for the deubiquitinating enzyme USP30.

Milon Mondal, Fangyuan Cao, Daniel Conole, Holger W Auner, Edward W Tate.

Ubiquitin-specific protease 30 (USP30) is a deubiquitinating enzyme (DUB) localized at the mitochondrial outer membrane and involved in PINK1/Parkin-mediated mitophagy, pexophagy, BAX/BAK-dependent apoptosis, and IKKβ-USP30-ACLY-regulated lipogenesis/tumorigenesis. A USP30 inhibitor, MTX652, has recently entered clinical trials as a potential treatment for mitochondrial dysfunction. Small molecule activity-based probes (ABPs) for DUBs have recently emerged as powerful tools for in-cell inhibitor screening and DUB activity analysis, and here, we report the first small molecule ABPs (IMP-2587 and IMP-2586) which can profile USP30 activity in cells. Target engagement studies demonstrate that IMP-2587 and IMP-2586 engage active USP30 at nanomolar concentration after only 10 min incubation time in intact cells, dependent on the presence of the USP30 catalytic cysteine. Interestingly, proteomics analyses revealed that DESI1 and DESI2, small ubiquitin-related modifier (SUMO) proteases, can also be engaged by these probes, further suggesting a novel approach to develop DESI ABPs.

DOI: https://doi.org/10.1039/d4cb00029c