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 4

GSK-3 regulates PINK1 splicing.

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GSK-3 regulates PINK1 splicing. (A) Venn diagram of genes differentially...
(A) Venn diagram of genes differentially expressed (blue) or differentially spliced (green) in CHIR-treated WT, SRSF2P95H/+, and SF3B1K700E/+ K562 cells relative to DMSO-treated controls. (B) Left: Sashimi plots of PINK1 in WT, SRSF2P95H/+, and SF3B1K700E/+ cells treated with DMSO or CHIR. Right: Bar graph shows intron 6 retention as a percentage of total transcripts. (C) PINK1 mRNA levels in WT, SRSF2P95H/+, and SF3B1K700E/+ cells treated with DMSO or 3 μM CHIR for 24 hours detected by RT-qPCR using primers that span exons 1 and 2 (mean ± SD). For data in B and C, *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001 (2-way ANOVA with Šidák’s multiple-comparison test). (D) PINK1 nascent transcript detection by RT-qPCR using primers for intron 1 (left) and intron 5 (right) in WT, SRSF2P95H/+, and SF3B1K700E/+ cells treated with DMSO or 3 μM CHIR for 24 hours. (E and F) Representative RT-PCR with primers spanning exon 6 (E6), intron 6 (I6), and exon 7 (E7) of PINK1 in WT, SRSF2P95H/+, and SF3B1K700E/+ K562 cells (E) and in CD34+ cells from healthy donors, primary AML cells, and CD34+ cells from CMML patients (F) treated with DMSO or 3 μM CHIR for 24 hours. PCR product with retained intron 6 is 568 bp, and product for spliced exon 6–7 (without retained intron) is 206 bp. M, DNA marker. (G) RT-PCR analysis of PINK1 splicing in WT, GSK3A/B-DKO, and GSK3A/B-DKO cells overexpressing GSK-3β (HEK293T). (H) UPF1 mRNA levels detected in K562 cells transduced with lentivirus expressing shRNA against UPF1 compared with non-targeting control (left), and levels of intron-retained and -spliced PINK1 mRNAs following UPF1 knockdown compared with control measured by RT-PCR (right). Data are presented as the mean ± SD. P value was determined by 2-tailed Student’s t test.