title: α-Solanine induces ROS-mediated autophagy through activation of endoplasmic reticulum stress and inhibition of Akt/mTOR pathway.
abstract: α-Solanine is a glycoalkaloid found in species of the nightshade family including potato. It was primarily reported to have toxic effects in humans. However, there is a growing body of literature demonstrating in vitro and in vivo anticancer activity of α-solanine. Most of these studies have shown activation of apoptosis as the underlying mechanism in antitumor activity of α-solanine. In this study, we report α-solanine as a potential inducer of autophagy, which may act synergistically or in parallel with apoptosis to exert its cytotoxic effect. Induction of autophagy was demonstrated by several assays including electron microscopy, immunoblotting of autophagy markers and immunofluorescence for LC3 (microtubule-associated protein 1 (MAP1) light chain-3) puncta. α-Solanine-induced autophagic flux was demonstrated by additionally enhanced--turnover of LC3-II and--accumulation of LC3-specific puncta after co-incubation of cells with either of the autophagolysosome inhibitors--chloroquine and--bafilomycin A1. We also demonstrated α-solanine-induced oxidative damage in regulating autophagy where pre-incubation of cells with reactive oxygen species (ROS) scavenger resulted in suppression of CM-H2DCFDA (5 (and 6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate acetyl ester) fluorescence as well as decrease in LC3-II turnover. α-Solanine treatment caused an increase in the expression of endoplasmic reticulum (ER) stress proteins (BiP, activating transcription factor 6 (ATF6), X-box-binding protein 1, PERK, inositol-requiring transmembrane kinase/endonuclease 1, ATF4 and CCAAT-enhancer-binding protein (C/EBP)-homologous protein) suggesting activation of unfolded protein response pathway. Moreover, we found downregulation of phosphorylated Akt (Thr308 and Ser473), mammalian target of rapamycin (mTOR; Ser2448 and Ser2481) and 4E-BP1 (Thr37/46) by α-solanine implying suppression of the Akt/mTOR pathway. Collectively, our results signify that α-solanine induces autophagy to exert anti-proliferative activity by triggering ER stress and inhibiting Akt/mTOR signaling pathway.
authors: Biochemistry Division, CSIR-Central Drug Research Institute, Lucknow, India.
authors: M
authors: M
authors: Hasanain
authors: Electron Microscopy Unit, CSIR-Central Drug Research Institute, Lucknow, India.
authors: A
authors: A
authors: Bhattacharjee
authors: Biochemistry Division, CSIR-Central Drug Research Institute, Lucknow, India.
authors: P
authors: P
authors: Pandey
authors: Biochemistry Division, CSIR-Central Drug Research Institute, Lucknow, India.
authors: R
authors: R
authors: Ashraf
authors: Biochemistry Division, CSIR-Central Drug Research Institute, Lucknow, India.
authors: N
authors: N
authors: Singh
authors: Biochemistry Division, CSIR-Central Drug Research Institute, Lucknow, India.
authors: S
authors: S
authors: Sharma
authors: Sophisticated Analytical Instruments Facilities, CSIR-Central Drug Research Institute, Lucknow, India.
authors: A L
authors: AL
authors: Vishwakarma
authors: Biochemistry Division, CSIR-Central Drug Research Institute, Lucknow, India.|Academy of Scientific and Innovative Research, Chennai, India.
authors: D
authors: D
authors: Datta
authors: Electron Microscopy Unit, CSIR-Central Drug Research Institute, Lucknow, India.|Academy of Scientific and Innovative Research, Chennai, India.
authors: K
authors: K
authors: Mitra
authors: Biochemistry Division, CSIR-Central Drug Research Institute, Lucknow, India.|Academy of Scientific and Innovative Research, Chennai, India.
authors: J
authors: J
authors: Sarkar
mesh_terms: D051701:Activating Transcription Factor 4 / Q000235:genetics / Q000378:metabolism; D051702:Activating Transcription Factor 6 / Q000235:genetics / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D000071190:Autophagy-Related Protein 8 Family; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D002738:Chloroquine / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D018942:Macrolides / Q000494:pharmacology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000819:agonists* / Q000378:metabolism; D000071701:Regulatory Factor X Transcription Factors; D015398:Signal Transduction; D012992:Solanine / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D056811:Unfolded Protein Response / Q000187:drug effects; D019892:eIF-2 Kinase / Q000235:genetics / Q000378:metabolism
chemical_list: C497109:ATF4 protein, human; C497111:ATF6 protein, human; D051702:Activating Transcription Factor 6; D048868:Adaptor Proteins, Signal Transducing; D000972:Antineoplastic Agents, Phytogenic; D000071190:Autophagy-Related Protein 8 Family; D022762:CCAAT-Enhancer-Binding Proteins; C515848:CEBPA protein, human; D004268:DNA-Binding Proteins; C498698:GABARAPL2 protein, human; C477012:MAP1LC3A protein, human; D018942:Macrolides; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; D017382:Reactive Oxygen Species; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; C514919:alpha-solanine; D051701:Activating Transcription Factor 4; D012992:Solanine; D002738:Chloroquine; C040929:bafilomycin A1; C546842:MTOR protein, human; C460640:EIF2AK3 protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D019892:eIF-2 Kinase