bp(GO:macroautophagy)
For instance, ubiquitin can recruit other factors to mediate various cellular responses such as signaling, gene regulation, endocytosis, macro-autophagy, and DNA repair PubMed:24457024
Consistent with a role of autophagy in disease, AD patient tissues exhibit impaired initiation of macroautophagy and an excess of autophagic vacuoles in dystrophic neurites, possibly due to impaired targeting of the vacuolar ATPase to the lysosome (86, 87). PubMed:25784053
Indeed, clioquinol countered disruption of autophagy by chloroquine in retinal cells, reduced Aβ42 accumulation in CHO cells expressing APP and mutant presenilin 1 and diminished amyloid misfolding and aggregation in Tg2576 AD mice 196,197 . PubMed:30116051
It increased expression of βGCase, normalized autophagy and accelerated degradation of α-synuclein in a stem cell model of dopaminergic neurons derived from patients with PD bearing mutations in βGCase 200 . PubMed:30116051
Indeed, clioquinol countered disruption of autophagy by chloroquine in retinal cells, reduced Aβ42 accumulation in CHO cells expressing APP and mutant presenilin 1 and diminished amyloid misfolding and aggregation in Tg2576 AD mice 196,197 . PubMed:30116051
Cilostazol (a phosphodiesterase 3 inhibitor) clears Aβ42 from neuronal cell lines by promoting autophagy, upregulating beclin 1, ATG5 and LC3, downregulating mTORC1 and inducing lysosomal cathepsin B; these actions of cilostazol involve activation of SIRT1 as well as upstream Tyr172 phosphorylation of AMPK 108,162,163 . PubMed:30116051
The natural product curcumin induced macro- autophagy and protected rotenone-treated dopaminer- gic neurons 141 in addition to accelerating the elimination of mutant α-synuclein-A53T by repressing mTORC1 in a cellular model of early-onset PD, although it also exerts other actions such as inhibition of p300-mediated pro- tein acetylation and of aggregation 142,143 . PubMed:30116051
Moreover, the flavonol fisetin stimulated auto- phagic degradation of phosphorylated tau in cortical neu- rons via mTORC1-dependent activation of TFEB and the cytoprotective transcription factor nuclear factor eryth- roid 2-related factor 2 (NFE2L2) 149 . Fisetin also reduced Aβ accumulation in an APP/PS1 mouse model of AD 150 . PubMed:30116051
Inactivation of ABL1 with brain-penetrant nilotinib conferred neuroprotective autophagy in mouse models of PD 153 . PubMed:30116051
An unusual approach to augmenting autophagosome formation is represented by the brain- penetrant autophagy enhancer 99 (AUTEN-99), which blocks myotubularin-related protein 14 (MTMR14, also known as Jumpy), a phosphatase that inhibits the phos- phoinositide 3-kinase (PI3K)-mediated generation of the autophagosome membrane (FIG. 3) . AUTEN-99 aug- mented autophagic flux in isolated neurons, increased markers of autophagy in mouse brain and slowed neuro- degeneration in D. melanogaster models of PD and HD 181 . PubMed:30116051
Disruption of this Bcl-2–beclin 1 complex is an alternative approach for promoting autophagy, as achieved in mouse fibroblasts by the BH3 mimetic ABT-737 (REF.177) . PubMed:30116051
The heterotrimeric serine/threonine kinase 5ʹ‑AMP‑ activated protein kinase (AMPK) and mammalian target of rapamycin complex 1 (mTORC1) trigger autophagy and repress mitophagy 3,10,20–23 (BOX 2; FIG. 3) . PubMed:30116051
The heterotrimeric serine/threonine kinase 5ʹ‑AMP‑ activated protein kinase (AMPK) and mammalian target of rapamycin complex 1 (mTORC1) trigger autophagy and repress mitophagy 3,10,20–23 (BOX 2; FIG. 3) . PubMed:30116051
One major strategy for promoting autophagy is the relief of its repression by mTORC1. PubMed:30116051
Tyrosine-protein kinase ABL1 is a proto- oncogene that negatively regulates autophagy, partly acting upstream of the RAC serine/threonine-protein kinase (AKT)–mTORC1 axis. PubMed:30116051
Other transcription factors that posi- tively regulate autophagy include forkhead box protein O1 (FOXO1) and FOXO3 (REF.22) . PubMed:30116051
Other transcription factors that posi- tively regulate autophagy include forkhead box protein O1 (FOXO1) and FOXO3 (REF.22) . PubMed:30116051
Supporting the relevance of sestrin 2, it has been shown to protect dopaminergic neurons from the neurotoxin rotenone via AMPK-transduced autophagy 247 . PubMed:30116051
Sestrin 2 over expression also prompted mTORC1-dependent autophagy in cortical neurons in a presenilin-knockout model of AD. PubMed:30116051
Because the class III deacetylase NAD- dependent protein deacetylase sirtuin 1 (SIRT1) requires nicotinamide adenine dinucleotide (NAD) to sustain its activity, this positive regulator of autophagy may also be considered a sensor 24 . PubMed:30116051
Conversely, repression is effected by signal transducer and activator of transcrip- tion 3 (STAT3) and possibly zinc-finger protein with KRAB and SCAN domains 3 (ZKSCAN3), although its role has been disputed 22,32 . PubMed:30116051
Unc-51-like kinase 1 (ULK1) is primarily an autophagy-initiating protein 3,10,19 , as is the mTORC1- suppressed transcrip- tion factor EB (TFEB), which orchestrates the synthesis of lysosomal and other proteins critical for maintaining ALN flux 20–23 . PubMed:30116051
mTORC1 also restrains autophagy by preventing nuclear translo- cation of TFEB 20 . PubMed:30116051
Unc-51-like kinase 1 (ULK1) is primarily an autophagy-initiating protein 3,10,19 , as is the mTORC1- suppressed transcrip- tion factor EB (TFEB), which orchestrates the synthesis of lysosomal and other proteins critical for maintaining ALN flux 20–23 . PubMed:30116051
Conversely, repression is effected by signal transducer and activator of transcrip- tion 3 (STAT3) and possibly zinc-finger protein with KRAB and SCAN domains 3 (ZKSCAN3), although its role has been disputed 22,32 . PubMed:30116051
We found that abundance of autophagic vacuoles (autophagosomes + autolysosomes) significantly increased in cells expressing either of the two tau mutants (Fig. 4d,e). This increase was mainly due to higher content of autolysosomes (red puncta) (Fig. 4d,e), in support of increased macroautophagic flux PubMed:29024336
In fact, increased macroautophagy may be responsible for the increase in the degradation of long-lived proteins that we observed for both mutant forms of tau under these conditions (Fig. 3b) PubMed:29024336
We found that abundance of autophagic vacuoles (autophagosomes + autolysosomes) significantly increased in cells expressing either of the two tau mutants (Fig. 4d,e). This increase was mainly due to higher content of autolysosomes (red puncta) (Fig. 4d,e), in support of increased macroautophagic flux PubMed:29024336
In fact, increased macroautophagy may be responsible for the increase in the degradation of long-lived proteins that we observed for both mutant forms of tau under these conditions (Fig. 3b) PubMed:29024336
A quite different strategy is to target tau clearance—e.g., by rapamycin that induces macroautophagy [175], inhibitors of Hsp90 chaperone protein that binds to misfolded proteins or by immunotherapeutic approaches [176]. PubMed:26751493
Protein clearance in animal models has been successfully demonstrated using several small molecules and drugs that enhance induction of macroautophagy reduces AD-relevant pathology, including rapamycin in 3xTGAD mice [32] and temsirolimus in P301S transgenic mice [156] and trehalose in APP/PS1 and P301S MAPT transgenic mice [157,158]. PubMed:29758300
For instance, while accumulation of Aβ activates the mTOR signaling pathway and subsequently blocks macroautophagy, rapamycin reduces the Aβ load by enhancing macroautophagy [32] PubMed:29758300
Methylene blue, a contrast agent that can reduce tau misfolding, has also been shown to induce macroautophagy, as indicated by elevated Beclin 1 and LC3-II levels and reduced tau and p62 levels in organotypic neuronal cultures and a mouse model of FTD [159] PubMed:29758300
Protein clearance in animal models has been successfully demonstrated using several small molecules and drugs that enhance induction of macroautophagy reduces AD-relevant pathology, including rapamycin in 3xTGAD mice [32] and temsirolimus in P301S transgenic mice [156] and trehalose in APP/PS1 and P301S MAPT transgenic mice [157,158]. PubMed:29758300
Decreased triglyceride breakdown upon macroautophagy inhibition and impairment in macroautophagy by lipid supplementation demonstrates reciprocally interrelated regulation of autophagy and lipids [72] PubMed:29758300
For instance, while accumulation of Aβ activates the mTOR signaling pathway and subsequently blocks macroautophagy, rapamycin reduces the Aβ load by enhancing macroautophagy [32] PubMed:29758300
Protein clearance in animal models has been successfully demonstrated using several small molecules and drugs that enhance induction of macroautophagy reduces AD-relevant pathology, including rapamycin in 3xTGAD mice [32] and temsirolimus in P301S transgenic mice [156] and trehalose in APP/PS1 and P301S MAPT transgenic mice [157,158]. PubMed:29758300
Under starvation or stress, TFEB translocates to the nucleus and binds the CRE element to promote expression of macroautophagy and lysosomal genes [88]. PubMed:29758300
For example, in tau A152T iPSC-derived cortical neurons, total and phosphorylated Tau levels are elevated, particularly the insoluble forms [133], which is associated with decreases in UPS function as measured by total polyubiquitinated proteins and an upregulation of macroautophagy markers. PubMed:29758300
Activation of PTEN, another inducer of macroautophagy, by TFEB is indispensable for this TFEB-mediated increase in macroautophagy [89] PubMed:29758300
Activation of PTEN, another inducer of macroautophagy, by TFEB is indispensable for this TFEB-mediated increase in macroautophagy [89] PubMed:29758300
Compromised macroautophagy, via the genetic suppression of Atg7, leads to the blockade of Aβ secretion and contributes to the subsequent diminution in extracellular Aβ plaque load PubMed:29758300
These results may be attributed to coincidental evidence of the involvement of Beclin 1 in VPS34-mediated trafficking pathways including macroautophagy and endocytosis [37], both of which are pronouncedly affected in AD pathology [38] PubMed:29758300
However, recent work provides direct evidence that PICALM can also modulate macroautophagy, via its role in SNARE endocytosis to clear tau aggregates [102]. PubMed:29758300
Recent work by Ulland et al. has also discovered an additional function of TREM2 in the maintenance of microglial macroautophagy and metabolism PubMed:29758300
VPS35 mutations have been shown to disrupt macroautophagy [113] and mitochondrial function [114] and are associated with AD and PD [102,115]. PubMed:29758300
Since Nixon and colleagues first reported the pathological evidence of defective macroautophagy in EM images in the AD brain, similar observations have been made in cellular and animal models of AD [2,3,7,14] PubMed:29758300
Defects in macroautophagy in AD are supported by additional lines of evidence PubMed:29758300
Maintenance of neuronal macroautophagy can counteract AD pathology [22,23]. PubMed:29758300
These results may be attributed to coincidental evidence of the involvement of Beclin 1 in VPS34-mediated trafficking pathways including macroautophagy and endocytosis [37], both of which are pronouncedly affected in AD pathology [38] PubMed:29758300
Finally, numerous studies using iPSC models have implicated changes in macroautophagy pathways in Parkinson’s disease [137–144], Gaucher disease [145], Niemann-Pick Type C1 disease [146–148] and diseases affecting motor neurons, including ALS [149,150], spinal and bulbar muscular atrophy (SBMA) [151], Brown- Vialetto disease [152], Charcot-Marie-Tooth 2A [153] and hereditary spastic paraplegia [154] PubMed:29758300
Finally, numerous studies using iPSC models have implicated changes in macroautophagy pathways in Parkinson’s disease [137–144], Gaucher disease [145], Niemann-Pick Type C1 disease [146–148] and diseases affecting motor neurons, including ALS [149,150], spinal and bulbar muscular atrophy (SBMA) [151], Brown- Vialetto disease [152], Charcot-Marie-Tooth 2A [153] and hereditary spastic paraplegia [154] PubMed:29758300
Finally, numerous studies using iPSC models have implicated changes in macroautophagy pathways in Parkinson’s disease [137–144], Gaucher disease [145], Niemann-Pick Type C1 disease [146–148] and diseases affecting motor neurons, including ALS [149,150], spinal and bulbar muscular atrophy (SBMA) [151], Brown- Vialetto disease [152], Charcot-Marie-Tooth 2A [153] and hereditary spastic paraplegia [154] PubMed:29758300
Finally, numerous studies using iPSC models have implicated changes in macroautophagy pathways in Parkinson’s disease [137–144], Gaucher disease [145], Niemann-Pick Type C1 disease [146–148] and diseases affecting motor neurons, including ALS [149,150], spinal and bulbar muscular atrophy (SBMA) [151], Brown- Vialetto disease [152], Charcot-Marie-Tooth 2A [153] and hereditary spastic paraplegia [154] PubMed:29758300
Finally, numerous studies using iPSC models have implicated changes in macroautophagy pathways in Parkinson’s disease [137–144], Gaucher disease [145], Niemann-Pick Type C1 disease [146–148] and diseases affecting motor neurons, including ALS [149,150], spinal and bulbar muscular atrophy (SBMA) [151], Brown- Vialetto disease [152], Charcot-Marie-Tooth 2A [153] and hereditary spastic paraplegia [154] PubMed:29758300
BAG1 targets proteins for degradation by the UPS, whereas BAG3 mediates degradation by macroautophagy. PubMed:23746257
Consistent with a role of autophagy in disease, AD patient tissues exhibit impaired initiation of macroautophagy and an excess of autophagic vacuoles in dystrophic neurites, possibly due to impaired targeting of the vacuolar ATPase to the lysosome (86, 87). PubMed:25784053
Moreover, the flavonol fisetin stimulated auto- phagic degradation of phosphorylated tau in cortical neu- rons via mTORC1-dependent activation of TFEB and the cytoprotective transcription factor nuclear factor eryth- roid 2-related factor 2 (NFE2L2) 149 . Fisetin also reduced Aβ accumulation in an APP/PS1 mouse model of AD 150 . PubMed:30116051
In this study, we analyzed the contribution of three different types of autophagy, macroautophagy, chaperone-mediated autophagy, and endosomal microautophagy to the degradation of tau protein variants and tau mutations associated with this agerelated disease. We have found that the pathogenic P301L mutation inhibits degradation of tau by any of the three autophagic pathways, whereas the risk-associated tau mutation A152T reroutes tau for degradation through a different autophagy pathway PubMed:29024336
Macroautophagy blockage resulted in preferential accumulation of A152T, but not WT and P301L tau (Fig. 2e,f) PubMed:29024336
Macroautophagy blockage resulted in preferential accumulation of A152T, but not WT and P301L tau (Fig. 2e,f) PubMed:29024336
Macroautophagy blockage resulted in preferential accumulation of A152T, but not WT and P301L tau (Fig. 2e,f) PubMed:29024336
The most notable difference between the two tau mutants was the inability of P301L to undergo degradation by CMA or by macroautophagy PubMed:29024336
In fact, increased macroautophagy may be responsible for the increase in the degradation of long-lived proteins that we observed for both mutant forms of tau under these conditions (Fig. 3b) PubMed:29024336
A quite different strategy is to target tau clearance—e.g., by rapamycin that induces macroautophagy [175], inhibitors of Hsp90 chaperone protein that binds to misfolded proteins or by immunotherapeutic approaches [176]. PubMed:26751493
Since Nixon and colleagues first reported the pathological evidence of defective macroautophagy in EM images in the AD brain, similar observations have been made in cellular and animal models of AD [2,3,7,14] PubMed:29758300
Defects in macroautophagy in AD are supported by additional lines of evidence PubMed:29758300
Maintenance of neuronal macroautophagy can counteract AD pathology [22,23]. PubMed:29758300
These results may be attributed to coincidental evidence of the involvement of Beclin 1 in VPS34-mediated trafficking pathways including macroautophagy and endocytosis [37], both of which are pronouncedly affected in AD pathology [38] PubMed:29758300
With neurons profoundly relying on macroautophagy for clearance of toxic protein aggregates, impairment in the proteolytic systems ultimately results in progressive neuronal death, a common feature in several neurodegenerative diseases [27]. PubMed:29758300
Lastly, macroautophagy, but not UPS or CMA can clear protein aggregates. PubMed:29758300
Increased Aβ generation and accumulation in lysosomes suggest that Aβ metabolism, at least partially, is regulated by macroautophagy [3,14,32–34]. PubMed:29758300
For instance, while accumulation of Aβ activates the mTOR signaling pathway and subsequently blocks macroautophagy, rapamycin reduces the Aβ load by enhancing macroautophagy [32] PubMed:29758300
In line with this, reduced Beclin 1 levels, as seen in AD models [16], increase the levels of intracellular and extracellular Aβ peptides, supporting the role of macroautophagy in the generation and degradation of Aβ [33,35]. PubMed:29758300
In line with this, reduced Beclin 1 levels, as seen in AD models [16], increase the levels of intracellular and extracellular Aβ peptides, supporting the role of macroautophagy in the generation and degradation of Aβ [33,35]. PubMed:29758300
Compromised macroautophagy, via the genetic suppression of Atg7, leads to the blockade of Aβ secretion and contributes to the subsequent diminution in extracellular Aβ plaque load PubMed:29758300
This inhibition of Aβ secretion during macroautophagy deficiency results in aberrant cytosolic accumulation of Aβ, which ultimately evokes neurodegeneration accompanied with memory loss. PubMed:29758300
These results may be attributed to coincidental evidence of the involvement of Beclin 1 in VPS34-mediated trafficking pathways including macroautophagy and endocytosis [37], both of which are pronouncedly affected in AD pathology [38] PubMed:29758300
Compromised macroautophagy, via the genetic suppression of Atg7, leads to the blockade of Aβ secretion and contributes to the subsequent diminution in extracellular Aβ plaque load PubMed:29758300
Wang et al., using an N2a neuroblastoma cell line that expresses the repeat domain of tau with an FTD-17 mutation (TauRDΔK280), has demonstrated that tau aggregates can be degraded by macroautophagy [48] PubMed:29758300
Decreased triglyceride breakdown upon macroautophagy inhibition and impairment in macroautophagy by lipid supplementation demonstrates reciprocally interrelated regulation of autophagy and lipids [72] PubMed:29758300
Finally, numerous studies using iPSC models have implicated changes in macroautophagy pathways in Parkinson’s disease [137–144], Gaucher disease [145], Niemann-Pick Type C1 disease [146–148] and diseases affecting motor neurons, including ALS [149,150], spinal and bulbar muscular atrophy (SBMA) [151], Brown- Vialetto disease [152], Charcot-Marie-Tooth 2A [153] and hereditary spastic paraplegia [154] PubMed:29758300
Finally, numerous studies using iPSC models have implicated changes in macroautophagy pathways in Parkinson’s disease [137–144], Gaucher disease [145], Niemann-Pick Type C1 disease [146–148] and diseases affecting motor neurons, including ALS [149,150], spinal and bulbar muscular atrophy (SBMA) [151], Brown- Vialetto disease [152], Charcot-Marie-Tooth 2A [153] and hereditary spastic paraplegia [154] PubMed:29758300
Finally, numerous studies using iPSC models have implicated changes in macroautophagy pathways in Parkinson’s disease [137–144], Gaucher disease [145], Niemann-Pick Type C1 disease [146–148] and diseases affecting motor neurons, including ALS [149,150], spinal and bulbar muscular atrophy (SBMA) [151], Brown- Vialetto disease [152], Charcot-Marie-Tooth 2A [153] and hereditary spastic paraplegia [154] PubMed:29758300
Finally, numerous studies using iPSC models have implicated changes in macroautophagy pathways in Parkinson’s disease [137–144], Gaucher disease [145], Niemann-Pick Type C1 disease [146–148] and diseases affecting motor neurons, including ALS [149,150], spinal and bulbar muscular atrophy (SBMA) [151], Brown- Vialetto disease [152], Charcot-Marie-Tooth 2A [153] and hereditary spastic paraplegia [154] PubMed:29758300
Finally, numerous studies using iPSC models have implicated changes in macroautophagy pathways in Parkinson’s disease [137–144], Gaucher disease [145], Niemann-Pick Type C1 disease [146–148] and diseases affecting motor neurons, including ALS [149,150], spinal and bulbar muscular atrophy (SBMA) [151], Brown- Vialetto disease [152], Charcot-Marie-Tooth 2A [153] and hereditary spastic paraplegia [154] PubMed:29758300
During macroautophagy, an elongated “isolation” membrane created from a preautophagosomal structure sequesters a region of cytoplasm to form a double- membrane-limited autophagosome (Fig. 5). PubMed:22908190
Incomplete charperone-mediated autophagy of tau generates fragments that aggregate and are cleared by macroautophagy (Wang et al. 2009). PubMed:22908190
These processes are distinguished from macroautophagy, in which an isolation membrane expands to engulf a portion of the cell, eventually fusing to form a new autophagic vacuole that subsequently fuses with a lysosome [12]. PubMed:18930136
The neuronal protein α-synuclein, for example, can be degraded by the UPS, macroautophagy and chaperone-mediated autophagy [26,29]. PubMed:18930136
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If you find BEL Commons useful in your work, please consider citing: Hoyt, C. T., Domingo-Fernández, D., & Hofmann-Apitius, M. (2018). BEL Commons: an environment for exploration and analysis of networks encoded in Biological Expression Language. Database, 2018(3), 1–11.