bp(GO:"proteasome-mediated ubiquitin-dependent protein catabolic process")
Thus, aggregation, which is the primary event, may lead to secondary damage by inhibiting the UPS (Bence et al., 2001). PubMed:14556719
Recent findings demonstrate that soluble aggregated proteins can inhibit the ubiquitin system (Bence et al., 2001) PubMed:14556719
For example, upregulation of the pathway is observed during massive degradation of skeletal muscle proteins that occurs under normal fasting but also under pathological conditions such as cancer-induced cachexia, severe sepsis, metabolic acidosis, or following denervation PubMed:14556719
The UPS can be regulated at the level of ubiquitination or at the level of proteasome activity PubMed:14556719
Lindquist and colleagues proposed that inhibition of UPS, which can be caused by ageing or following a pharmacological treatment, can lead to accumulation of PrPc in the cytoplasm where it is spontaneously converted into a PrPsc-like species because it is not rapidly degraded by the UPS (Hooper, 2003; Ma and Lindquist,2002;Ma et al., 2002). PubMed:14556719
The UPS can be regulated at the level of ubiquitination or at the level of proteasome activity PubMed:14556719
Another study has also demonstrated that UPS inhibition is only revealed under conditions of increased stress in cells expressing mutant Huntingtin (Ding et al., 2002) PubMed:14556719
Similarly, overexpression of the putative SOD1 E3 ligase dorfin can inhibit cell death induced by the mutant protein (Niwa et al., 2002), presumably by promoting its removal via the UPS. PubMed:14556719
The simple explanation is that the mutation leads to a shortage in free ubiquitin that should have been recycled from conjugates, which results in general impairment of the function of the UPS. PubMed:14556719
Taken together, several lines of evidence point to a reduced UPS function in AD and suggest that both Abeta and tau are important players in the game. PubMed:14556719
Several apparently independent aberrations linked to defects in the UPS have been described in various rare forms of hereditary PD PubMed:14556719
Recent work has highlighted a novel possible role for failure of the UPS in initiating prion disease, which can explain the cause of some cases of sporadic prion disease. PubMed:14556719
The model proposed by Lindquist and collaborators is important as it identifies malfunction of UPS as a potentially important player in prion pathogenesis PubMed:14556719
Seventh, Aβ42 obstructs the UPS and CMA 47,68 . PubMed:30116051
Finally, mirroring its inhibitory influence on the ALN, mTORC1 suppresses the UPS by impeding the formation and assembly of proteasomal subunits. PubMed:30116051
In addition, CMA is disrupted by sev- eral genetic mutations occurring in PD, including muta- tions in LRRK2 (REFS2,3,45–47,55,69,80) . PubMed:30116051
The UPS and CMA are disrupted by neurotoxic proteins like Aβ42 and tau, hence, their early and preventive reinforcement prior to Aβ42 and tau accumulation may be critical. PubMed:30116051
Furthermore, mutations in the gene encoding parkin and several other genes are linked to reduced UPS activity 2,56,69,79,80 . PubMed:30116051
Recent evidence has shown that dysfunction in the UPS is closely related with tau degradation/aggregation and neurodedeneration in AD. PubMed:23528736
Recent evidence has shown that dysfunction in the UPS is closely related with tau degradation/aggregation and neurodedeneration in AD. PubMed:23528736
However, their dysfunction in AD due to some factors will reduce Aβ clearance PubMed:29626319
Tau aggregates can be targeted by two protein clearance pathways, the UPS and the A-LS, with the latter pathway encompassing microautophagy,CMA and macroautophagy. 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
Impairment in the UPS is cardinal to the development of neurodegeneration, in part because of its reciprocal interplay with protein aggregation PubMed:29758300
The earliest symptoms of AD are believed to be due to synaptic dysfunction, and in this context, numerous studies have established a significant role of the UPS in the regulation of synaptic plasticity. PubMed:22908190
The UPS is also critically involved in learning and memory. PubMed:22908190
The UPS is also critically involved in learning and memory. PubMed:22908190
Indeed, transgenic mice expressing UBB+1 have an impaired UPS and show contextual memory deficits in both water maze and fear conditioning paradigms, without specific neuropathological findings (Fischer et al. 2009). PubMed:22908190
The resulting polyubiquitinated UBB+1 cannot be degraded by proteasomes and impairs the UPS (Lam et al. 2000), which may induce neurotoxicity. PubMed:22908190
BAG1 targets proteins for degradation by the UPS, whereas BAG3 mediates degradation by macroautophagy. PubMed:23746257
In addition to aggresome formation, impairment of the UPS in vitro has been found to induce autophagy [63,64]. PubMed:18930136
Although the mechanism whereby autophagy and UPS function are coordinated is little understood, several regulators have emerged as important players in mediating this crosstalk, including histone deacetylase 6 (HDAC6) [50,64,75], p62/sequestosome 1 (p62) [76], and the FYVE-domain containing protein Alfy [77]; notably, these proteins have all been found to regulate or be essential for aggresome formation PubMed:18930136
Although the mechanism whereby autophagy and UPS function are coordinated is little understood, several regulators have emerged as important players in mediating this crosstalk, including histone deacetylase 6 (HDAC6) [50,64,75], p62/sequestosome 1 (p62) [76], and the FYVE-domain containing protein Alfy [77]; notably, these proteins have all been found to regulate or be essential for aggresome formation PubMed:18930136
Thus, it has been suggested that p62 provides a key link between autophagy and the UPS by facilitating autophagic degradation of ubiquitinated proteins. PubMed:18930136
Although the mechanism whereby autophagy and UPS function are coordinated is little understood, several regulators have emerged as important players in mediating this crosstalk, including histone deacetylase 6 (HDAC6) [50,64,75], p62/sequestosome 1 (p62) [76], and the FYVE-domain containing protein Alfy [77]; notably, these proteins have all been found to regulate or be essential for aggresome formation PubMed:18930136
Indeed, experimental evidence indicates that neurodegeneration is frequently associated with impaired UPS function, although whether this is a cause or consequence of neurodegeneration is a contested issue, as is reviewed elsewhere in this special issue PubMed:18930136
Several apparently independent aberrations linked to defects in the UPS have been described in various rare forms of hereditary PD PubMed:14556719
Miller and colleagues (Miller et al., 2003) have recently shown that this mutation destabilizes DJ-1 via promotion of its rapid, UPS-mediated degradation PubMed:14556719
Taken together, several lines of evidence point to a reduced UPS function in AD and suggest that both Abeta and tau are important players in the game. PubMed:14556719
Recent work has highlighted a novel possible role for failure of the UPS in initiating prion disease, which can explain the cause of some cases of sporadic prion disease. PubMed:14556719
The model proposed by Lindquist and collaborators is important as it identifies malfunction of UPS as a potentially important player in prion pathogenesis PubMed:14556719
Lindquist and colleagues proposed that inhibition of UPS, which can be caused by ageing or following a pharmacological treatment, can lead to accumulation of PrPc in the cytoplasm where it is spontaneously converted into a PrPsc-like species because it is not rapidly degraded by the UPS (Hooper, 2003; Ma and Lindquist,2002;Ma et al., 2002). PubMed:14556719
Once in the cytoplasm, the PrPc would be efficiently degraded by the UPS via the ERAD pathway, but this does not occur in the presence of the proteasome inhibitors PubMed:14556719
The mutant SOD1 proteins, unlike the wild-type form, are degraded by the UPS (Hoffman et al., 1996;Johnston et al., 2000). PubMed:14556719
Similarly, overexpression of the putative SOD1 E3 ligase dorfin can inhibit cell death induced by the mutant protein (Niwa et al., 2002), presumably by promoting its removal via the UPS. PubMed:14556719
Urushitani and coworkers (Urushitani et al., 2002) showed that mutant SOD1 is degraded by the UPS in cultured cells and that oxidative damage increases the degree of ubiquitination of mutant but not of wild-type SOD1. PubMed:14556719
Consequently, the formation of aggregates may increase when the UPS fails PubMed:14556719
This indicates that the truncated fragments are normally processed via the UPS, and therefore the disposal of fragments of mutant proteins will be impaired. PubMed:14556719
Interestingly, the UPS is important for elimination of tau and other neurotoxic proteins in post synaptic dendritic compartments (a key site of spreading), where it plays a more general role favouring synaptic plasticity, den- dritogenesis and memory formation 49,52 . PubMed:30116051
Interestingly, the UPS is important for elimination of tau and other neurotoxic proteins in post synaptic dendritic compartments (a key site of spreading), where it plays a more general role favouring synaptic plasticity, den- dritogenesis and memory formation 49,52 . PubMed:30116051
Interestingly, the UPS is important for elimination of tau and other neurotoxic proteins in post synaptic dendritic compartments (a key site of spreading), where it plays a more general role favouring synaptic plasticity, den- dritogenesis and memory formation 49,52 . PubMed:30116051
Interestingly, the UPS is important for elimination of tau and other neurotoxic proteins in post synaptic dendritic compartments (a key site of spreading), where it plays a more general role favouring synaptic plasticity, den- dritogenesis and memory formation 49,52 . PubMed:30116051
Recent evidence has shown that dysfunction in the UPS is closely related with tau degradation/aggregation and neurodedeneration in AD. PubMed:23528736
Recent evidence has shown that dysfunction in the UPS is closely related with tau degradation/aggregation and neurodedeneration in AD. PubMed:23528736
Intracellular protein degradation is performed by UPS and ALS (Wong and Cuervo 2010 PubMed:29626319
Under physiological conditions, UPS, located in the cytosol and the nucleus in eukaryotic cells, as a major intracellular short-lived protein degradation system (Schwartz and Ciechanover 2009), mediates the clearance of misfolded or other abnormally modified proteins with the help of ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2), ubiquitin ligase (E3), and the 26S proteasome for the sake of preventing the accumulation of toxic substances (Shang and Taylor 2011) PubMed:29626319
Intracellular Aβ clearance can be achieved through UPS and ALS, and extracellular Aβ is degraded by glial phagocytosis, such as microglia, astrocytes, and proteases from neurons and astrocytes (Fig. 2) PubMed:29626319
Intracellular Aβ degradation pathways mainly contain two major pathways: UPS and ALS (Vilchez et al. 2014) PubMed:29626319
Dysfunction of UPS brings about the deposition of hyperphosphorylated tau oligomers in synapses (Tai et al. 2012) PubMed:29626319
Impairment in the UPS is cardinal to the development of neurodegeneration, in part because of its reciprocal interplay with protein aggregation PubMed:29758300
For instance, phosphorylated insoluble tau proteins dampen 26S proteasome activity, while activation of the UPS attenuates tauopathy [27] PubMed:29758300
Tau aggregates can be targeted by two protein clearance pathways, the UPS and the A-LS, with the latter pathway encompassing microautophagy,CMA and macroautophagy. PubMed:29758300
These experimental differences may be attributed to the intricate interplay between the UPS and autophagy, as α-synuclein is degraded by both proteolytic systems [62,63]. PubMed:29758300
It has recently become appreciated that ubiquitination of proteins by covalent modification tags them for elimination not only through the proteasome (the ubiquitin–proteasome system or UPS) but also through the lysosomal system. PubMed:22908190
The earliest symptoms of AD are believed to be due to synaptic dysfunction, and in this context, numerous studies have established a significant role of the UPS in the regulation of synaptic plasticity. PubMed:22908190
The UPS is also critically involved in learning and memory. PubMed:22908190
The UPS is also critically involved in learning and memory. PubMed:22908190
This and numerous related findings suggest that degradation of certain critical proteins by the UPS is required during long-term memory formation. One of these proteins is arc, a negative regulator of synaptic strength that promotes the internalization of AMPA receptors and is degraded via the E3 ligase, UBE3A (Greer et al. 2010). PubMed:22908190
This and numerous related findings suggest that degradation of certain critical proteins by the UPS is required during long-term memory formation. One of these proteins is arc, a negative regulator of synaptic strength that promotes the internalization of AMPA receptors and is degraded via the E3 ligase, UBE3A (Greer et al. 2010). PubMed:22908190
UPS-mediated catabolism is also essential to mainten amino acid pools in acute starvation and contributes significantly to the degradation of defective proteins [1,2,7]. PubMed:18930136
UPS-mediated catabolism is also essential to mainten amino acid pools in acute starvation and contributes significantly to the degradation of defective proteins [1,2,7]. PubMed:18930136
This role in recycling is complementary to that of the UPS, which degrades proteins to generate oligopeptides that are subsequently degraded into amino acids while replenishing the cell’s supply of free ubiquitin. PubMed:18930136
This role in recycling is complementary to that of the UPS, which degrades proteins to generate oligopeptides that are subsequently degraded into amino acids while replenishing the cell’s supply of free ubiquitin. PubMed:18930136
Indeed, experimental evidence indicates that neurodegeneration is frequently associated with impaired UPS function, although whether this is a cause or consequence of neurodegeneration is a contested issue, as is reviewed elsewhere in this special issue PubMed:18930136
In the case of α-synuclein, for example, Webb et al. concluded that soluble forms of the disease protein are efficiently degraded by the UPS, while aggregated or oligomeric α-synuclein require autophagy for clearance [26]. PubMed:18930136
The neuronal protein α-synuclein, for example, can be degraded by the UPS, macroautophagy and chaperone-mediated autophagy [26,29]. PubMed:18930136
In addition to aggresome formation, impairment of the UPS in vitro has been found to induce autophagy [63,64]. PubMed:18930136
In cells that are exposed to stressors such as starvation or UPS inhibition, Alfy relocalizes from the nuclear envelope to filamentous cytoplasmic structures that are near autophagic membranes and ubiquitinated protein inclusions, as well as within autophagosomes [77]. PubMed:18930136
The two major pathways for protein degradation in cells are through the ubiquitin-proteasome system and the autophagy-lysosome system [10, 11], both of which have been implicated in tau degradation in AD [12]. PubMed:25374103
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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.