title: Harmol induces autophagy and subsequent apoptosis in U251MG human glioma             cells through the downregulation of survivin.
abstract: The β-carboline alkaloids are plant substances that exhibit a wide spectrum             of neuropharmacological, psychopharma-cological and antitumor effects. In the             present study, we found that harmol, a β-carboline alkaloid, induced autophagy             and suppression of survivin expression, and subsequently induced apoptotic cell             death in U251MG human glioma cells. Autophagy was induced within 12 h by treatment             with harmol. When treated for over 36 h, however, apoptotic cell death was induced.             Harmol treatment also reduced survivin protein expression. Small interfering RNA             (siRNA)-mediated knockdown of survivin enhanced the harmol-induced apoptosis.             Knockdown of survivin by siRNA also induced autophagy. Therefore, harmol-induced             apoptosis is a result of the reduction in survivin protein expression. Treatment             with 3-methyladenine (3-MA) in the presence of harmol did not affect the expression             of survivin and diminished harmol-induced cell death. Treatment with chloroquine             in the presence of harmol did not suppress the reduction of survivin expression             and increased harmol-induced cell death. From these results, harmol-induced reduction             of survivin expression was closely related to autophagy. It is assumed that when             isolation membrane formation is inhibited by treatment with 3-MA, reduction of             survivin protein expression and apoptotic cell death were not induced. However,             when isolation membrane formation is started and an autophagosome is formed, survivin             expression is suppressed and apoptosis is executed. Harmol treatment reduced phosphorylation             of Akt, mammalian target of rapamycin (mTOR) and its downstream targets p70-ribosomal             protein S6 kinase and 4E-binding protein 1, resulting in induction of autophagy.             Conversely, activation of the Akt/mTOR pathway inhibited harmol-induced autophagy             and cell death. These findings indicate that harmol-induced autophagy involves             the Akt/mTOR pathway. Taken together, autophagy induced by harmol represented             a pro-apoptotic mechanism, and harmol suppressed the expression of survivin and             subsequently induced apoptosis.
authors: Department of Biochemistry, Tokyo Medical University, Shinjuku-ku, Tokyo 160-8402, Japan. aabe-bc@tokyo-med.ac.jp
authors: Akihisa
authors: A
authors: Abe
authors: Hiroko
authors: H
authors: Kokuba
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics*; D001343:Autophagy / Q000187:drug effects; D001932:Brain Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005910:Glioma / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D006247:Harmine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics* / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering; D015398:Signal Transduction; D000077022:Survivin; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
chemical_list: C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D034741:RNA, Small Interfering; D000077022:Survivin; C001326:harmol; D006247:Harmine; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases