Search

Mitophagy must be carefully regulated to ensure that cells maintain appropriate numbers of functional mitochondria. The SCFFBXL4 ubiquitin ligase complex suppresses mitophagy by controlling the degradation of BNIP3 and NIX mitophagy receptors, and FBXL4 mutations result in mitochondrial disease as a consequence of elevated mitophagy. Here, we reveal that the mitochondrial phosphatase PPTC7 is an essential cofactor for SCFFBXL4-mediated destruction of BNIP3 and NIX, suppressing both steady-state and induced mitophagy. Disruption of the phosphatase activity of PPTC7 does not influence BNIP3 and NIX turnover. Rather, a pool of PPTC7 on the mitochondrial outer membrane acts as an adaptor linking BNIP3 and NIX to FBXL4, facilitating the turnover of these mitophagy receptors. PPTC7 accumulates on the outer mitochondrial membrane in response to mitophagy induction or the absence of FBXL4, suggesting a homoeostatic feedback mechanism that attenuates high levels of mitophagy. We mapped critical residues required for PPTC7-BNIP3/NIX and PPTC7-FBXL4 interactions and their disruption interferes with both BNIP3/NIX degradation and mitophagy suppression. Collectively, these findings delineate a complex regulatory mechanism that restricts BNIP3/NIX-induced mitophagy.

Objectives: Molecular diagnostics and care of non-small cell lung cancer (NSCLC) are continuously evolving. Few data document the current strategies to manage advanced NSCLC patients beyond progression in clinical practice. Patients and methods: Be-TeaM is an Italian multi-center observational study conducted on consecutive EGFR-mutated stage IV NSCLC patients, progressed during/after a first-line EGFR-TKI. It consists of a retrospective phase, from first-line EGFR-TKI therapy start until study entry (i.e. beginning of the diagnostic process), and a prospective phase, until treatment choice or for 3 months if no therapy was prescribed. Primary objective was to describe the diagnostic and therapeutic approaches adopted after progression in a real-world setting. Results: Of 308 patients enrolled in 63 centers from July 2017 to June 2018, 289 were included in the analysis. In first line, 53.3 % received gefitinib, 32.5 % afatinib and 14.2 % erlotinib. The testing rate (i.e. rate of all patients undergone any biopsy -liquid and/or tissue- for the T790 M detection) was 90.7 %, with liquid biopsy being the most frequently executed. Of 262 biopsied patients, 64.5 % underwent only 1 liquid biopsy, 10.7 % only 1 tissue biopsy and 18.3 % >1 biopsy, both liquid and solid in 85.4 %. The T790M positivity rate was 45.3 %; of 166 patients undergone only a liquid biopsy and tested for the mutation, 39.8 % were T790M+ and 60.2 % T790M-/undetermined. By the observation end, 87.9 % patients had a post-progression treatment chosen, osimertinib being the most frequent among the T790M+. Conclusion: Be-TeaM provides the first snapshot of current practices for the management of NSCLC patients beyond progression in Italy; in clinical practice, assessing the T790M status is not always feasible.