Abstract
Pathological protein inclusions containing the microtubule-associated protein tau, ubiquitin, and a variety of heat shock proteins, originating in oligodendrocytes, are consistent features observed in a number of neurodegenerative diseases. Defects in the proteolytic degradation systems have been associated with protein aggregate formation. The ubiquitin proteasome system (UPS) and autophagy are critically involved in the maintenance of cellular homeostasis and their activities need to be carefully balanced. A genuine crosstalk exists between the UPS and the autophagosomal system, and when the UPS is impaired, autophagy might act as a compensatory mechanism. Autophagy represents a lysosomal degradation system for degrading long-lived proteins and organelles, including damaged mitochondria. As we have shown before, proteasomal impairment by the reversible proteasomal inhibitor MG-132 (carbobenzoxy-l-leucyl-l-leucyl-l-leucinal) in oligodendrocytes leads to protein aggregate formation and apoptotic cell death, caused by activation of caspases and the mitochondrial pathway. The present study was undertaken to elucidate whether upregulation of the autophagic pathway by rapamycin can protect oligodendrocytes and ameliorate the consequences of MG-132-induced protein aggregate formation. The data show that rapamycin attenuated the formation of dense protein aggregates, but did not enhance the survival capability of oligodendrocytes after proteasomal inhibition. After activation of the autophagic pathway in combination with proteasomal inhibition, caspase 3 activation and poly(ADP-ribose) polymerase-1 cleavage were even more pronounced than after proteasomal inhibition alone. Furthermore, rapamycin augmented MG-132-induced activation of extracellular signal-regulated kinases 1 and 2, which are involved in the regulation of cell death and survival. In summary, depending on the cellular context and system, rapamycin may promote cell survival or, under other conditions in concert with apoptosis, may augment cell death, which seems to be the case in oligodendrocytes. Its therapeutic use for neurodegenerative disorders is most likely limited, since long-term administration may impair neuronal survival and specifically damage the myelin forming cells of the CNS.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Bauer NG, Richter-Landsberg C (2006) The dynamic instability of microtubules is required for aggresome formation in oligodendroglial cells after proteolytic stress. J Mol Neurosci 29:153–168
Berger Z, Ravikumar B, Menzies FM et al (2006) Rapamycin alleviates toxicity of different aggregate-prone proteins. Hum Mol Genet 15:433–442
Bjorkoy G, Lamark T, Brech A et al (2005) p62/SQSTM1 forms protein aggregates degraded by autophagy and has a protective effect on huntingtin-induced cell death. J Cell Biol 171:603–614
Bove J, Martinez-Vicente M, Vila M (2011) Fighting neurodegeneration with rapamycin: mechanistic insights. Nat Rev Neurosci 12:437–452
Caccamo A, Magri A, Medina DX et al (2013) mTOR regulates tau phosphorylation and degradation: implications for Alzheimer's disease and other tauopathies. Aging Cell 12:370–380
Chaitanya GV, Steven AJ, Babu PP (2010) PARP-1 cleavage fragments: signatures of cell-death proteases in neurodegeneration. Cell Commun Signal 8:31
Dehay B, Bove J, Rodriguez-Muela N et al (2010) Pathogenic lysosomal depletion in Parkinson's disease. J Neurosci 30:12535–12544
Ding WX, Ni HM, Gao W et al (2007) Linking of autophagy to ubiquitin-proteasome system is important for the regulation of endoplasmic reticulum stress and cell viability. Am J Pathol 171:513–524
Dohm CP, Kermer P, Bahr M (2008) Aggregopathy in neurodegenerative diseases: mechanisms and therapeutic implication. Neurodegener Dis 5:321–338
Ghavami S, Shojaei S, Yeganeh B et al (2014) Autophagy and apoptosis dysfunction in neurodegenerative disorders. Prog Neurobiol 112:24–49
Goldbaum O, Richter-Landsberg C (2004) Proteolytic stress causes heat shock protein induction, tau ubiquitination, and the recruitment of ubiquitin to tau-positive aggregates in oligodendrocytes in culture. J Neurosci 24:5748–5757
Goldbaum O, Vollmer G, Richter-Landsberg C (2006) Proteasome inhibition by MG-132 induces apoptotic cell death and mitochondrial dysfunction in cultured rat brain oligodendrocytes but not in astrocytes. Glia 53:891–901
Janen SB, Chaachouay H, Richter-Landsberg C (2010) Autophagy is activated by proteasomal inhibition and involved in aggresome clearance in cultured astrocytes. Glia 58:1766–1774
Jellinger KA (2012) Interaction between pathogenic proteins in neurodegenerative disorders. J Cell Mol Med 16:1166–1183
Jiang J, Jiang J, Zuo Y, Gu Z (2013) Rapamycin protects the mitochondria against oxidative stress and apoptosis in a rat model of Parkinson's disease. Int J Mol Med 31:825–832
Johnson SC, Martin GM, Rabinovitch PS, Kaeberlein M (2013) Preserving youth: does rapamycin deliver? Sci Transl Med 5:211fs40
Keller JN, Gee J, Ding Q (2002) The proteasome in brain aging. Ageing Res Rev 1:279–293
Klionsky DJ, Abdalla FC, Abeliovich H et al (2012) Guidelines for the use and interpretation of assays for monitoring autophagy. Autophagy 8:445–544
Komatsu M, Ichimura Y (2010) Physiological significance of selective degradation of p62 by autophagy. FEBS Lett 584:1374–1378
Korolchuk VI, Menzies FM, Rubinsztein DC (2010) Mechanisms of cross-talk between the ubiquitin-proteasome and autophagy-lysosome systems. FEBS Lett 584:1393–1398
Lansbury PT, Lashuel HA (2006) A century-old debate on protein aggregation and neurodegeneration enters the clinic. Nature 443:774–779
Lee SJ, Lim HS, Masliah E, Lee HJ (2011) Protein aggregate spreading in neurodegenerative diseases: problems and perspectives. Neurosci Res 70:339–348
Luo X, Kraus WL (2012) On PAR with PARP: cellular stress signaling through poly(ADP-ribose) and PARP-1. Genes Dev 26:417–432
Maiuri MC, Zalckvar E, Kimchi A, Kroemer G (2007) Self-eating and self-killing: crosstalk between autophagy and apoptosis. Nat Rev Mol Cell Biol 8:741–752
Majumder S, Richardson A, Strong R, Oddo S (2011) Inducing autophagy by rapamycin before, but not after, the formation of plaques and tangles ameliorates cognitive deficits. PLoS One 6:e25416
Malagelada C, Jin ZH, Jackson-Lewis V, Przedborski S, Greene LA (2010) Rapamycin protects against neuron death in in vitro and in vivo models of Parkinson's disease. J Neurosci 30:1166–1175
Mizushima N, Yoshimori T, Levine B (2010) Methods in mammalian autophagy research. Cell 140:313–326
Mukhopadhyay S, Panda PK, Sinha N, Das DN, Bhutia SK (2014) Autophagy and apoptosis: where do they meet? Apoptosis 19:555–566
Narayanan SP, Flores AI, Wang F, Macklin WB (2009) Akt signals through the mammalian target of rapamycin pathway to regulate CNS myelination. J Neurosci 29:6860–6870
Neuhoff V, Philipp K, Zimmer HG, Mesecke S (1979) A simple, versatile, sensitive and volume-independent method for quantitative protein determination which is independent of other external influences. Hoppe Seylers Z Physiol Chem 360:1657–1670
Nixon RA (2006) Autophagy in neurodegenerative disease: friend, foe or turncoat? Trends Neurosci 29:528–535
Pandey UB, Nie Z, Batlevi Y et al (2007) HDAC6 rescues neurodegeneration and provides an essential link between autophagy and the UPS. Nature 447:859–863
Pankiv S, Clausen TH, Lamark T et al (2007) p62/SQSTM1 binds directly to Atg8/LC3 to facilitate degradation of ubiquitinated protein aggregates by autophagy. J Biol Chem 282:24131–24145
Ravikumar B, Berger Z, Vacher C, O'Kane CJ, Rubinsztein DC (2006) Rapamycin pre-treatment protects against apoptosis. Hum Mol Genet 15:1209–1216
Richter-Landsberg C (2008) The cytoskeleton in oligodendrocytes. Microtubule dynamics in health and disease. J Mol Neurosci 35:55–63
Richter-Landsberg C, Heinrich M (1996) OLN-93: a new permanent oligodendroglia cell line derived from primary rat brain glial cultures. J Neurosci Res 45:161–173
Richter-Landsberg C, Leyk J (2013) Inclusion body formation, macroautophagy, and the role of HDAC6 in neurodegeneration. Acta Neuropathol 126:793–807
Riedel M, Goldbaum O, Schwarz L, Schmitt S, Richter-Landsberg C (2010) 17-AAG induces cytoplasmic alpha-synuclein aggregate clearance by induction of autophagy. PLoS One 5:e8753
Santos RX, Correia SC, Cardoso S, Carvalho C, Santos MS, Moreira PI (2011) Effects of rapamycin and TOR on aging and memory: implications for Alzheimer's disease. J Neurochem 117:927–936
Sarbassov DD, Ali SM, Sengupta S et al (2006) Prolonged rapamycin treatment inhibits mTORC2 assembly and Akt/PKB. Mol Cell 22:159–168
Sarkar S, Ravikumar B, Floto RA, Rubinsztein DC (2009) Rapamycin and mTOR-independent autophagy inducers ameliorate toxicity of polyglutamine-expanded huntingtin and related proteinopathies. Cell Death Differ 16:46–56
Schwartz AL, Ciechanover A (2009) Targeting proteins for destruction by the ubiquitin system: implications for human pathobiology. Annu Rev Pharmacol Toxicol 49:73–96
Schwarz L, Goldbaum O, Bergmann M, Probst-Cousin S, Richter-Landsberg C (2012) Involvement of macroautophagy in multiple system atrophy and protein aggregate formation in oligodendrocytes. J Mol Neurosci 47:256–266
Settembre C, Di Malta C, Polito VA et al (2011) TFEB links autophagy to lysosomal biogenesis. Science 332:1429–1433
Shinojima N, Yokoyama T, Kondo Y, Kondo S (2007) Roles of the Akt/mTOR/p70S6K and ERK1/2 signaling pathways in curcumin-induced autophagy. Autophagy 3:635–637
Tyler WA, Gangoli N, Gokina P et al (2009) Activation of the mammalian target of rapamycin (mTOR) is essential for oligodendrocyte differentiation. J Neurosci 29:6367–6378
Wirawan E, Vande Walle L, Kersse K et al (2010) Caspase-mediated cleavage of Beclin-1 inactivates Beclin-1-induced autophagy and enhances apoptosis by promoting the release of proapoptotic factors from mitochondria. Cell Death Dis 1:e18
Xilouri M, Stefanis L (2011) Autophagic pathways in Parkinson disease and related disorders. Expert Rev Mol Med 13:e8
Zhang X, Li L, Chen S et al (2011) Rapamycin treatment augments motor neuron degeneration in SOD1(G93A) mouse model of amyotrophic lateral sclerosis. Autophagy 7:412–425
Zhu J, Horbinski C, Guo F, Watkins S, Uchiyama Y, Chu CT (2007) Regulation of autophagy by extracellular signal-regulated protein kinases during 1-methyl-4phenylpyridinium-induced cell death. American J Pathol 170:75–86
Zhu Y, Zhao L, Liu L et al (2010) Beclin 1 cleavage by caspase 3 inactivates autophagy and promotes apoptosis. Protein Cell 1:468–477
Acknowledgments
This work was supported by the German Science Foundation (DFG RI 384/17-1). We thank Irina Fomins and Angelika Spanjer for the excellent technical help and Dr. Olaf Goldbaum for the helpful discussions.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Noack, M., Richter-Landsberg, C. Activation of Autophagy by Rapamycin Does Not Protect Oligodendrocytes Against Protein Aggregate Formation and Cell Death Induced by Proteasomal Inhibition. J Mol Neurosci 55, 99–108 (2015). https://doi.org/10.1007/s12031-014-0380-x
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s12031-014-0380-x