Morphology, clearing efficacy, and mTOR dependency of the organelle autophagoproteasome


The interplay between autophagy (ATG) and ubiquitin proteasome (UP) cell-clearing systems was recently evidenced at biochemical and morphological levels, where subunits belonging to both pathways co-localize within a novel organelle named autophagoproteasome (APP). We previously documented that APP occurs at baseline conditions, while it is hindered by neurotoxicant administration. This is bound to the activity of the mechanistic target of rapamycin (mTOR), since APP is stimulated by mTOR inhibition, which in turn, is correlated with cell protection. In this brief report, we provide novel, morphological and biochemical evidence on APP, suggesting the presence of active UP subunits within ATG vacuoles. Although a stream of interpretation considers such a merging as a catabolic pathway to clear inactive UP subunits, our data further indicate that UP-ATG merging may rather provide an empowered catalytic organelle.



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Klionsky DJ, Emr SD. Autophagy as a regulated pathway of cellular degradation. Science 2000;290:1717–21. DOI:

Speese SD, Trotta N, Rodesch CK, Aravamudan B, Broadie K. The ubiquitin proteasome system acutely regulates presynaptic protein turnover and synaptic efficacy. Curr Biol 2003;13:899–910. DOI:

Hegde AN. The ubiquitin-proteasome pathway and synaptic plasticity. Learn Mem 2010;17:314–27. DOI:

Münz C. Autophagy proteins in antigen processing for presentation on MHC molecules. Immunol Rev 2016;272:17–27. DOI:

Münz C. The macroautophagy machinery in endo- and exocytosis. J Mol Biol 2017;429:473-85. DOI:

Vijayan V, Verstreken P. Autophagy in the presynaptic compartment in health and disease. J Cell Biol 2017;216:1895–906. DOI:

Limanaqi F, Gambardella S, Biagioni F, Busceti CL, Fornai F. Epigenetic effects induced by methamphetamine and methamphetamine-dependent oxidative stress. Oxid Med Cell Longev 2018;2018:4982453. DOI:

Limanaqi F, Biagioni F, Gambardella S, Ryskalin L, Fornai F. Interdependency between autophagy and synaptic vesicle trafficking: implications for dopamine release. Front Mol Neurosci 2018,11:299. DOI:

Limanaqi F, Biagioni F, Busceti CL, Ryskalin L, Fornai F. The effects of proteasome on baseline and methamphetamine-dependent dopamine transmission. Neurosci Biobehav Rev 2019;102:308-317. DOI:

Limanaqi F, Biagioni F, Busceti CL, Ryskalin L, Polzella M, Frati A, et al. Phytochemicals bridging autophagy induction and alpha-synuclein degradation in Parkinsonism. Int J Mol Sci 2019;20:3274. DOI:

Limanaqi F, Biagioni F, Gaglione A, Busceti CL, Fornai F. A sentinel in the crosstalk between the nervous and immune system: The (immuno)-proteasome. Front Immunol 2019;10:628. DOI:

Limanaqi F, Biagioni F, Busceti CL, Ryskalin L, Soldani P, Frati A, et al. Cell clearing systems bridging neuro-immunity and synaptic plasticity. Int J Mol Sci 2019;20:2197. DOI:

Liang Y. Emerging concepts and functions of autophagy as a regulator of synaptic components and plasticity. Cells 2019;8:34. DOI:

Limanaqi F, Biagioni F, Gambardella S, Familiari P, Frati A, Fornai F. Promiscuous roles of autophagy and proteasome in neurodegenerative proteinopathies. Int J Mol Sci 2020;21:3028. DOI:

Limanaqi F, Busceti CL, Biagioni F, Lazzeri G, Forte M, Schiavon S, et al. Cell clearing systems as targets of polyphenols in viral infections: Potential implications for COVID-19 pathogenesis. Antioxidants (Basel) 2020;9:1105. DOI:

Fornai F, Lenzi P, Gesi M, Ferrucci M, Lazzeri G, Capobianco L, et al. Similarities between methamphetamine toxicity and proteasome inhibition. Ann N Y Acad Sci 2004;1025:162-70. DOI:

Fornai F, Schlüter O, Lenzi P, Gesi M, Ruffoli R, Ferrucci M, et al. Parkinson-like syndrome induced by continuous MPTP infusion: Convergent roles of the ubiquitin-proteasome system and alpha-synuclein. Proc Natl Acad Sci USA 2005;102:3413–8. DOI:

Fornai F, Lazzeri G, Bandettini Di Poggio A., Soldani P, De Blasi A, Nicoletti F, et al. Convergent roles of alpha-synuclein, DA metabolism, and the ubiquitin-proteasome system in nigrostriatal toxicity. Ann N Y Acad Sci 2006;1074:84–9. DOI:

Lazzeri G, Lenzi P, Gesi M, Ferrucci M, Fulceri F, Ruggieri S, et al. In PC12 Cells Neurotoxicity Induced by Methamphetamine Is Related to Proteasome Inhibition. Ann N Y Acad Sci 2006;1074:174–7. DOI:

Lazzeri G, Lenzi P, Busceti CL, Ferrucci M, Falleni A, Bruno V, et al. Mechanisms involved in the formation of dopamine-induced intracellular bodies within striatal neurons. J Neurochem 2007;101:1414–27. DOI:

Castino R, Lazzeri G, Lenzi P, Bellio N, Follo C, Ferrucci M, et al. Suppression of autophagy precipitates neuronal cell death following low doses of methamphetamine. J Neurochem 2008;106:1426–39. DOI:

Mashimoto T, Hadjebi O, Amair-Pinedo F, Tsurumi T, Langa F, Serikawa T, et al. Progressive Purkinje cell degeneration in tambaleante mutant mice is a consequence of a missense mutation in HERC1 E3 ubiquitin ligase. PLoS Genet 2009;5:e1000784. DOI:

Friedman LG, Lachenmayer ML, Wang J, He L, Poulose SM, Komatsu M, et al. Disrupted autophagy leads to dopaminergic axon and dendrite degeneration and promotes presynaptic accumulation of α-synuclein and LRRK2 in the brain. J Neurosci 2012;32:7585–93. DOI:

Ruiz R, Pérez-Villegas EM, Bachiller S, Rosa JL, Armengol JA. HERC 1 Ubiquitin ligase mutation affects neocortical, CA3 hippocampal and spinal cord projection neurons: An ultrastructural study. Front Neuroanat 2016;10:42. DOI:

Sato S, Uchihara T, Fukuda T, Noda S, Kondo H, Saiki S, et al. Loss of autophagy in dopaminergic neurons causes Lewy pathology and motor dysfunction in aged mice. Sci Rep 2018;8:2813. DOI:

Zhao J, Zhai B, Gygi SP, Goldberg AL. mTOR inhibition activates overall protein degradation by the ubiquitin proteasome system as well as by autophagy. Proc Natl Acad Sci USA 2015;112:15790–7. DOI:

Cohen-Kaplan V, Livneh I, Avni N, Fabre B, Ziv T, Kwon YT, et al. p62-and ubiquitin-dependent stress-induced autophagy of the mammalian 26S proteasome. Proc Natl Acad Sci USA 2016;113:E7490–9. DOI:

Lenzi P, Lazzeri G, Biagioni F, Busceti CL, Gambardella S, Salvetti A, et al. The autophagoproteasome a novel cell clearing organelle in baseline and stimulated conditions. Front Neuroanat 2016;10:78. DOI:

Lazzeri G, Biagioni F, Fulceri F, Busceti CL, Scavuzzo MC, Ippolito C, et al. mTOR modulates methamphetamine-induced toxicity through cell clearing systems. Oxid Med Cell Longev 2018; 2018:6124745. DOI:

Seibenhener ML, Babu JR, Geetha T, Wong HC, Krishna NR, Wooten MW. Sequestosome 1/p62 is a polyubiquitin chain binding protein involved in ubiquitin proteasome degradation. Mol Cell Biol 2004;24:8055–68. DOI:

Liu WJ, Ye L, Huang WF, Guo LJ, Xu ZG, Wu HL et al. p62 links the autophagy pathway and the ubiqutin-proteasome system upon ubiquitinated protein degradation. Cell Mol Biol Lett 2016;21:29. DOI:

Otero MG, Alloatti M, Cromberg LE, Almenar-Queralt A, Encalada SE, Pozo Devoto VM, et al. Fast axonal transport of the proteasome complex depends on membrane interaction and molecular motor function. J Cell Sci 2014;127:1537–49. DOI:

Klionsky DJ, Abdelmohsen K, Abe A, Abedin MJ, Abeliovich H, Acevedo Arozena A, et al. Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition). Autophagy 2021;17:1-382. DOI:

Marshall RS, Li F, Gemperline DC, Vierstra RD. Autophagic degradation of the 26S proteasome is mediated by the dual ATG8/ubiquitin receptor RPN10 in arabidopsis. Mol Cell 2015;58:1053-66. DOI:

Bendayan M, Zollinger M. Ultrastructural localization of antigenic sites on osmium-fixed tissues applying the protein A-gold technique. J Histochem Cytochem 1983;31:101-9. DOI:

D'Alessandro D, Mattii L, Moscato S, Bernardini N, Segnani C, Dolfi A, et al. Immunohistochemical demonstration of the small GTPase RhoAA on epoxy-resin embedded sections. Micron 2004;35:287–96. DOI:

Fornai F, Gesi M, Saviozzi M, Lenzi P, Piaggi S, Ferrucci M, et al. Immunohistochemical evidence and ultrastructural compartmentalization of a new antioxidant enzyme in the rat substantia nigra. J Neurocytol 2001;30:97-105. DOI:

Fornai F, Lenzi P, Gesi M, Soldani P, Ferrucci M, Lazzeri G, et al. Methamphetamine produces neuronal inclusions in the nigrostriatal system and in PC12 cells. J Neurochem 2003;88:114–23. DOI:

Supporting Agencies
Ministero della Salute (Ricerca Corrente)
Autophagy, proteasome, LC3, Beclin 1, P20S, alpha-synuclein, transmission electron microscopy, confocal microscopy
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How to Cite
Limanaqi, F., Biagioni, F., Salvetti, A., Puglisi-Allegra, S., Lenzi, P., & Fornai, F. (2021). Morphology, clearing efficacy, and mTOR dependency of the organelle autophagoproteasome. European Journal of Histochemistry, 65(s1).