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Published on: December 26, 2016
miR-495-3p regulates sphingolipid metabolic reprogramming to induce Sphk1/ceramide mediated mitophagy and apoptosis
Shweta Arora1, Prithvi Singh2, Gulnaz Tabassum1
1Translational Research Lab, Department of Biotechnology, Faculty of Natural Sciences, Jamia Millia Islamia, New Delhi, 110025, India.
Abstract:
Sphingolipid metabolism is the forefront area of cancer research, but the underlying mechanisms are not fully explored yet. Sphingolipid metabolites [ceramide, sphingosine-1-phosphate (S1P)] are critical players in cell growth and apoptosis. Sphk1 is a key enzyme, catalyzing the phosphorylation of sphingosine to S1P, favoring cell proliferation and survival. Contrarily, ceramide induces cell cycle arrest and apoptosis. Sphk1 also exerts regulatory roles in numerous cellular processes, wherein microRNAs (miRNAs) play a momentous role. However, miR-mediated regulation of Sphk1 in Non-small cell lung cancer (NSCLC), continues to be elusive. miR-495 is highly downregulated and worsens NSCLC prognosis. The present study demonstrates Sphk1 upregulation and poor prognosis in NSCLC. However, miR-495-3p directly targets Sphk1, and possesses tumor-suppressive roles by decreasing cell proliferation, wound healing, colony formation, LDH-A activity, and inducing G0/G1 phase cell cycle arrest upon restoration. Besides, we also found ceramide accretion upon Sphk1 inhibition, leading to mitochondrial dysregulation. We found a cogent upregulation of Drp-1, PARK2 and LC3β, along with degradation of PINK1 and Mfn2, demonstrating an imbalance in mitochondrial fission/fusion and induction of mitophagy, even during PINK1 deficiency. Later, we found a reduction in mitochondrial energy homeostasis, mitochondrial membrane potential, increased ROS generation and ultimately initiation of apoptosis, upon miR-495-3p overexpression. Overall, we showed that miR-495-3p reprograms sphingolipid rheostat towards ceramide by targeting Sphk1 and induces lethal mitophagy to suppress NSCLC tumorigenesis. The study identified a miR-mediated mechanism of sphingolipid reprogramming that could be beneficial in designing novel therapeutic strategies for NSCLC.
Insights
MicroRNA-495-3p targets Sphingosine kinase 1 (Sphk1) in non-small cell lung cancer (NSCLC). Restoring miR-495-3p suppresses tumor growth by altering sphingolipid metabolism and inducing mitophagy.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- Sphingolipid metabolism is crucial in cancer, with metabolites like ceramide and sphingosine-1-phosphate (S1P) regulating cell fate.
- Sphingosine kinase 1 (Sphk1) promotes cancer cell proliferation and survival by producing S1P.
- MicroRNAs (miRNAs) regulate gene expression, but their role in Sphk1-mediated non-small cell lung cancer (NSCLC) is unclear.
Purpose of the Study:
- To investigate the role of miR-495-3p in regulating Sphk1 in NSCLC.
- To elucidate the underlying mechanisms by which miR-495-3p exerts tumor-suppressive effects.
Main Methods:
- Analysis of Sphk1 and miR-495-3p expression in NSCLC.
- In vitro assays to assess cell proliferation, migration, and colony formation.
- Mitochondrial function assays, including assessment of fission/fusion dynamics and mitophagy.
- Western blotting to detect key proteins involved in sphingolipid metabolism and mitochondrial pathways.
Main Results:
- Sphk1 is upregulated in NSCLC, correlating with poor prognosis.
- miR-495-3p directly targets and downregulates Sphk1, suppressing NSCLC cell proliferation and migration.
- miR-495-3p restoration leads to ceramide accumulation, mitochondrial dysfunction, and mitophagy induction.
- Overexpression of miR-495-3p reduces mitochondrial membrane potential, increases ROS, and induces apoptosis.
Conclusions:
- miR-495-3p acts as a tumor suppressor in NSCLC by targeting Sphk1.
- This microRNA reprograms sphingolipid metabolism towards ceramide and triggers mitophagy, inhibiting tumor growth.
- The findings reveal a novel miRNA-mediated mechanism for sphingolipid reprogramming with therapeutic potential for NSCLC.
