Autophagy Is Involved in the Viability of Overexpressing Thioredoxin o1 Tobacco BY-2 Cells under Oxidative Conditions

Phytol and α-Bisabolol Synergy Induces Autophagy and Apoptosis in A549 Cells and Additional Molecular Insights through Comprehensive Proteome Analysis via Nano LC-MS/MS

BACKGROUND

Non-Small Cell Lung Cancer (NSCLC) is a malignancy with a significant prevalence and aggressive nature, posing a considerable challenge in terms of therapeutic interventions. Autophagy and apoptosis, two intricate cellular processes, are integral to NSCLC pathophysiology, each affecting the other through shared signaling pathways. Phytol (Phy) and α-bisabolol (Bis) have shown promise as potential anticancer agents individually, but their combined effects in NSCLC have not been extensively investigated.

OBJECTIVE

The present study was to examine the synergistic impact of Phy and Bis on NSCLC cells, particularly in the context of autophagy modulation, and to elucidate the resulting differential protein expression using LCMS/ MS analysis.

METHODS

The A549 cell lines were subjected to the patented effective concentration of Phy and Bis, and subsequently, the viability of the cells was evaluated utilizing the MTT assay. The present study utilized real-time PCR analysis to assess the expression levels of crucial apoptotic genes, specifically Bcl-2, Bax, and Caspase-9, as well as autophagy-related genes, including Beclin-1, SQSTM1, Ulk1, and LC3B. The confirmation of autophagy marker expression (Beclin-1, LC3B) and the autophagy-regulating protein SQSTM1 was achieved through the utilization of Western blot analysis. Differentially expressed proteins were found using LC-MS/MS analysis.

RESULTS

The combination of Phy and Bis demonstrated significant inhibition of NSCLC cell growth, indicating their synergistic effect. Real-time PCR analysis revealed a shift towards apoptosis, with downregulation of Bcl-2 and upregulation of Bax and Caspase-9, suggesting a shift towards apoptosis. Genes associated with autophagy regulation, including Beclin-1, SQSTM1 (p62), Ulk1, and LC3B, showed significant upregulation, indicating potential induction of autophagy. Western blot analysis confirmed increased expression of autophagy markers, such as Beclin-1 and LC3B, while the autophagy-regulating protein SQSTM1 exhibited a significant decrease. LC-MS/MS analysis revealed differential expression of 861 proteins, reflecting the modulation of cellular processes. Protein-protein interaction network analysis highlighted key proteins involved in apoptotic and autophagic pathways, including STOML2, YWHAB, POX2, B2M, CDA, CAPN2, TXN, ECHS1, PEBP1, PFN1, CDC42, TUBB1, HSPB1, PXN, FGF2, and BAG3, emphasizing their crucial roles. Additionally, PANTHER pathway analysis uncovered enriched pathways associated with the differentially expressed proteins, revealing their involvement in a diverse range of biological processes, encompassing cell signaling, metabolism, and cellular stress responses.

CONCLUSION

The combined treatment of Phy and Bis exerts a synergistic inhibitory effect on NSCLC cell growth, mediated through the interplay of apoptosis and autophagy. The differential protein expression observed, along with the identified proteins and enriched pathways, provides valuable insights into the underlying molecular mechanisms. These findings offer a foundation for further exploration of the therapeutic potential of Phy and Bis in the management of NSCLC.

Thioredoxin TRXo1 is involved in ABA perception via PYR1 redox regulation

Abscisic acid (ABA) plays a fundamental role in plant growth and development processes such as seed germination, stomatal response or adaptation to stress, amongst others. Increases in the endogenous ABA content is recognized by specific receptors of the PYR/PYL/RCAR family that are coupled to a phosphorylation cascade targeting transcription factors and ion channels. Just like other receptors of the family, nuclear receptor PYR1 binds ABA and inhibits the activity of type 2C phosphatases (PP2Cs), thus avoiding the phosphatase-exerted inhibition on SnRK2 kinases, positive regulators which phosphorylate targets and trigger ABA signalling. Thioredoxins (TRXs) are key components of cellular redox homeostasis that regulate specific target proteins through a thiol-disulfide exchange, playing an essential role in redox homeostasis, cell survival, and growth. In higher plants, TRXs have been found in almost all cellular compartments, although its presence and role in nucleus has been less studied. In this work, affinity chromatography, Dot-blot, co-immunoprecipitation, and bimolecular fluorescence complementation assays allowed us to identify PYR1 as a new TRXo1 target in the nucleus. Studies on recombinant HisAtPYR1 oxidation-reduction with wild type and site-specific mutagenized forms showed that the receptor underwent redox regulation involving changes in the oligomeric state in which Cys³⁰ and Cys⁶⁵ residues were implied. TRXo1 was able to reduce previously-oxidized inactive PYR1, thus recovering its capacity to inhibit HAB1 phosphatase. In vivo PYR1 oligomerization was dependent on the redox state, and a differential pattern was detected in KO and over-expressing Attrxo1 mutant plants grown in the presence of ABA compared to WT plants. Thus, our findings suggest the existence of a redox regulation of TRXo1 on PYR1 that may be relevant for ABA signalling and had not been described so far.

Hydrogen sulfide action in the regulation of plant autophagy

Hydrogen sulfide is a signaling molecule with a well-established impact on both plant and animal physiology. Intense investigation into the regulation of autophagy by sulfide in Arabidopsis thaliana has revealed that the post-translational modification of persulfidation/S-sulfhydration plays a key role. In this review focused on plants, we discuss the nature of the sulfide molecule involved in the regulation of autophagy, the final outcome of this modification, and the persulfidated autophagy proteins identified so far. A detailed outline of the actual knowledge of the regulation mechanism of the autophagy-related proteins ATG4a and ATG18a from Arabidopsis by sulfide is also included. This information will be instrumental for furthering research on the regulation of autophagy by sulfide.