Sulforaphane downregulated fatty acid synthase and inhibited microtubule-mediated mitophagy leading to apoptosis

Yuting Yan,Zhongnan Zheng,Lei Li,Yabin Hu,Wei Wu,Yan Zhou,Juntao Li

doi:10.1038/s41419-021-04198-2

Abstract

We previously demonstrated that sulforaphane (SFN) inhibited autophagy leading to apoptosis in human non-small cell lung cancer (NSCLC) cells, but the underlying subcellular mechanisms were unknown. Hereby, high-performance liquid chromatography-tandem mass spectrometry uncovered that SFN regulated the production of lipoproteins, and microtubule- and autophagy-associated proteins. Further, highly expressed fatty acid synthase (FASN) contributed to cancer malignancy and poor prognosis. Results showed that SFN depolymerized microtubules, downregulated FASN, and decreased its binding to α-tubulin; SFN downregulated FASN, acetyl CoA carboxylase (ACACA), and ATP citrate lyase (ACLY) via activating proteasomes and downregulating transcriptional factor SREBP1; SFN inhibited the interactions among α-tubulin and FASN, ACACA, and ACLY; SFN decreased the amount of intracellular fatty acid (FA) and mitochondrial phospholipids; and knockdown of FASN decreased mitochondrial membrane potential (ΔΨm) and increased reactive oxygen species, mitochondrial abnormality, and apoptosis. Further, SFN downregulated mitophagy-associated proteins Bnip3 and NIX, and upregulated mitochondrial LC3 II/I. Transmission electron microscopy showed mitochondrial abnormality and accumulation of mitophagosomes in response to SFN. Combined with mitophagy inducer CCCP or autophagosome–lysosome fusion inhibitor Bafilomycin A1, we found that SFN inhibited mitophagosome–lysosome fusion leading to mitophagosome accumulation. SFN reduced the interaction between NIX and LC3 II/I, and reversed CCCP-caused FA increase. Furthermore, knockdown of α-tubulin downregulated NIX and BNIP3 production, and upregulated LC3 II/I. Besides, SFN reduced the interaction and colocalization between α-tubulin and NIX. Thus, SFN might cause apoptosis via inhibiting microtubule-mediated mitophagy. These results might give us a new insight into the mechanisms of SFN-caused apoptosis in the subcellular level.

Highlights

We reported that sulforaphane (SFN) metabolite-induced microtubule disruption contributed to the inhibition of cell proliferation and autophagy leading to apoptosis [1, 2]
The level of fatty acid (FA) synthase (FASN) in tumor tissues is higher than that in adjacent tissues (Fig. 1F). These results suggested that SFN-caused apoptosis might result from the downregulation of FA synthesis-associated proteins and the dysfunction of microtubule- and autophagy-associated proteins, and membrane proteins
Here we found that SFN inhibited microtubule-mediated FA synthesis and mitophagy resulting in decreased FA, mitochondrial dysfunction, and apoptosis

Summary

Introduction

We reported that sulforaphane (SFN) metabolite-induced microtubule disruption contributed to the inhibition of cell proliferation and autophagy leading to apoptosis [1, 2]. SFN might cause swollen mitochondria in non-small cell lung cancer (NSCLC) [3]. Report showed that abnormal lipid metabolism might cause cell apoptosis [4]. De novo synthesis is the main pathway for cancer cells to produce fatty acids (FAs); FA synthase (FASN) is highly expressed in various cancers including lung cancer and low production of FASN in NSCLC patients have longer survival [5,6,7]. Study showed that downregulation of FASN production caused apoptosis in tumor cells rather than normal cells [8]. FAs are essential components of biofilm lipids and are important substrates for energy metabolism [9,10,11]; tumor cells require large amounts of FAs for rapid division and proliferation [12, 13]

Methods

Results

Conclusion