A mitochondrial surveillance mechanism activated by SRSF2 mutations in hematologic malignancies
Xiaolei Liu, … , Omar Abdel-Wahab, Peter S. Klein
Xiaolei Liu, … , Omar Abdel-Wahab, Peter S. Klein
Published May 7, 2024
Citation Information: J Clin Invest. 2024;134(12):e175619. https://doi.org/10.1172/JCI175619.
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Research Article Hematology Oncology

A mitochondrial surveillance mechanism activated by SRSF2 mutations in hematologic malignancies

Abstract

Splicing factor mutations are common in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), but how they alter cellular functions is unclear. We show that the pathogenic SRSF2P95H/+ mutation disrupts the splicing of mitochondrial mRNAs, impairs mitochondrial complex I function, and robustly increases mitophagy. We also identified a mitochondrial surveillance mechanism by which mitochondrial dysfunction modifies splicing of the mitophagy activator PINK1 to remove a poison intron, increasing the stability and abundance of PINK1 mRNA and protein. SRSF2P95H-induced mitochondrial dysfunction increased PINK1 expression through this mechanism, which is essential for survival of SRSF2P95H/+ cells. Inhibition of splicing with a glycogen synthase kinase 3 inhibitor promoted retention of the poison intron, impairing mitophagy and activating apoptosis in SRSF2P95H/+ cells. These data reveal a homeostatic mechanism for sensing mitochondrial stress through PINK1 splicing and identify increased mitophagy as a disease marker and a therapeutic vulnerability in SRSF2P95H mutant MDS and AML.

Authors

Xiaolei Liu, Sudhish A. Devadiga, Robert F. Stanley, Ryan M. Morrow, Kevin A. Janssen, Mathieu Quesnel-Vallières, Oz Pomp, Adam A. Moverley, Chenchen Li, Nicolas Skuli, Martin Carroll, Jian Huang, Douglas C. Wallace, Kristen W. Lynch, Omar Abdel-Wahab, Peter S. Klein

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Figure 5

SRSF2P95H increases PINK1 expression and mitophagy.

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SRSF2P95H increases PINK1 expression and mitophagy. (A) Heatmap shows z...
(A) Heatmap shows z-scored expression of mitophagy-related genes in WT and SRSF2P95H/+ K562 cells. (B) Left: Representative confocal images of mitochondria (green, TOMM20+) and lysosomes (red, LAMP1+) in K562 WT or SRSF2P95H/+ cells treated with DMSO or 3 μM CHIR for 2 days. Scale bar: 10 μm. Right: Bar plot shows quantification of the colocalization of mitochondria with lysosomes (n = 5 fields for each group; n = 3). (C) Left: Representative transmission electron microscopy images of WT and SRSF2P95H/+ K562 cells treated with DMSO or 3 μM CHIR for 2 days. Scale bar: 0.5 μm. Right: Bar plot shows quantification of the number of autophagic vacuoles per cell. Each circle represents one cell. (D) Bar graph shows mitophagic flux determined by MitoTracker green (MTG) staining in WT and SRSF2P95H/+ K562 treated with or without 2 μM CHIR for 48 hours. Mitochondrial net flux was calculated by mitochondrial accumulation in the presence of 100 μM chloroquine (CQ) or 50 μM Lys05 for 4 hours (31). Data are presented as the mean ± SD. For data in B–D, **P < 0.01 and ***P < 0.001 (2-way ANOVA with Šidák’s multiple-comparison test). (E) Immunoblotting of PINK1 and β-catenin in WT and SRSF2P95H/+ cells treated with DMSO or 3 μM CHIR for indicated times. (F) Violin plot of OPTN and TOMM7 normalized expression in AML patients in TCGA data set (n = 581) with or without mutations in SRSF2. Statistical analysis was performed using 2-tailed Mann-Whitney test.