Nigericin-induced impairment of autophagic flux in neuronal cells is inhibited by overexpression of Bak

Junghyun Lim, Yunsu Lee, Hyun Wook Kim, Im Joo Rhyu, Myung Sook Oh, Moussa B.H. Youdim, Zhenyu Yue, Young J. Oh

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24 Citations (Scopus)


Bak is a prototypic pro-apoptotic Bcl-2 family protein expressed in a wide variety of tissues and cells. Recent studies have revealed that Bcl-2 family proteins regulate apoptosis as well as autophagy. To investigate whether and how Bak exerts a regulatory role on autophagy-related events, we treated independent cell lines, including MN9D neuronal cells, with nigericin, a K +/H+ ionophore. Treatment of MN9D cells with nigericin led to an increase of LC3-II and p62 levels with concomitant activation of caspase. Ultrastructural examination revealed accumulation of autophagic vacuoles and swollen vacuoles in nigericin-treated cells. We further found that the LC3-II accumulated as a consequence of impaired autophagic flux and the disrupted degradation of LC3-II in nigericin-treated cells. In this cell death paradigm, both transient and stable overexpression of various forms of Bak exerted a protective role, whereas it did not inhibit the extent of nigericin-mediated activation of caspase-3. Subsequent biochemical and electron microscopic studies revealed that overexpressed Bak maintained autophagic flux and reduced the area occupied by swollen vacuoles in nigericin- treated cells. Similar results were obtained in nigericin-treated non-neuronal cells and another proton ionophore-induced cell death paradigm. Taken together, our study indicates that a protective role for Bak during ionophore-induced cell death may be closely associated with its regulatory effect on maintenance of autophagic flux and vacuole homeostasis.

Original languageEnglish
Pages (from-to)23271-23282
Number of pages12
JournalJournal of Biological Chemistry
Issue number28
Publication statusPublished - 2012 Jul 6

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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