Abstract
Cell differentiation is often associated with decreased cell growth, indicating an altered rate of macromolecule synthesis and degradation. In this study, we present evidence that autophagy, a process for bulk degradation of cytoplasm, is activated during retinoic acid-induced neuronal differentiation of neuroblastoma N2a cells. Chemical inhibitors of autophagy, including 3-MA and LY294002, abrogate cell differentiation. RNA interference of autophagy gene beclin 1 markedly delays the process of differentiation. We also find that cell differentiation is accompanied by decreased activity of mTOR, a major controller of cell growth and a negative regulator of autophagy. However, completely inhibiting mTOR by rapamycin decreases neurite outgrowth, cell size and the immunoreactivity for neuronal markers. Our study suggests that an appropriate level of mTOR activity is important in cell differentiation for a balance between macromolecule synthesis and degradation.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenine / analogs & derivatives
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Adenine / pharmacology
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Animals
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Apoptosis Regulatory Proteins
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Autophagy* / drug effects
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Autophagy* / genetics
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Beclin-1
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Carrier Proteins / metabolism*
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Cell Differentiation* / drug effects
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Cell Differentiation* / genetics
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Cell Line, Tumor
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Cell Size
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Chromones / pharmacology
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Dose-Response Relationship, Drug
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Down-Regulation
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Mice
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Morpholines / pharmacology
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Neurites / metabolism
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Neurites / pathology
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Neuroblastoma / enzymology
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Neuroblastoma / metabolism
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Neuroblastoma / pathology*
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Neurons / drug effects
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Neurons / enzymology
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Neurons / metabolism
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Neurons / pathology*
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Phosphotransferases (Alcohol Group Acceptor) / metabolism*
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Protein Kinases / metabolism*
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Proteins / genetics
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Proteins / metabolism
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Proto-Oncogene Proteins c-akt / metabolism
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RNA Interference
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RNA, Small Interfering / metabolism
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Signal Transduction* / drug effects
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Signal Transduction* / genetics
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Sirolimus / pharmacology
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TOR Serine-Threonine Kinases
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Time Factors
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Tretinoin / pharmacology
Substances
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Apoptosis Regulatory Proteins
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Beclin-1
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Becn1 protein, mouse
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Carrier Proteins
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Chromones
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Morpholines
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Proteins
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RNA, Small Interfering
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2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
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3-methyladenine
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Tretinoin
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Protein Kinases
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Phosphotransferases (Alcohol Group Acceptor)
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mTOR protein, mouse
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Proto-Oncogene Proteins c-akt
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TOR Serine-Threonine Kinases
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Adenine
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Sirolimus