scholarly journals Role for the Ubiquitin-Proteasome System in the Vacuolar Degradation of Ste6p, the a-Factor Transporter in Saccharomyces cerevisiae

1998 ◽  
Vol 18 (2) ◽  
pp. 779-789 ◽  
Author(s):  
Diego Loayza ◽  
Susan Michaelis
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Membrane Protein ◽  
Intracellular Trafficking ◽  
Ubiquitin Proteasome System ◽  
Atp Binding ◽  
Dependent Manner ◽  
Binding Domains ◽  
Ubiquitin Proteasome ◽  
Metabolic Degradation ◽  
Polytopic Membrane Protein

ABSTRACT Ste6p, the a-factor transporter in Saccharomyces cerevisiae, is a multispanning membrane protein with 12 transmembrane spans and two cytosolic ATP binding domains. Ste6p belongs to the ATP binding cassette (ABC) superfamily and provides an excellent model for examining the intracellular trafficking of a complex polytopic membrane protein in yeast. Previous studies have shown that Ste6p undergoes constitutive endocytosis from the plasma membrane, followed by delivery to the vacuole, where it is degraded in a Pep4p-dependent manner, even though only a small portion of Ste6p is exposed to the vacuolar lumen where the Pep4p-dependent proteases reside. Ste6p is known to be ubiquitinated, a modification that may facilitate its endocytosis. In the present study, we further investigated the intracellular trafficking of Ste6p, focusing on the role of the ubiquitin-proteasome machinery in the metabolic degradation of Ste6p. We demonstrate by pulse-chase analysis that the degradation of Ste6p is impaired in mutants that exhibit defects in the activity of the proteasome (doa4 andpre1,2). Likewise, by immunofluorescence, we observe that Ste6p accumulates in the vacuole in thedoa4 mutant, as it does in the vacuolar protease-deficient pep4 mutant. One model consistent with our results is that the degradation of Ste6p, the bulk of which is exposed to the cytosol, requires the activity of both the cytosolic proteasomal degradative machinery and the vacuolar lumenal proteases, acting in a synergistic fashion. Alternatively, we discuss a second model whereby the ubiquitin-proteasome system may indirectly influence the Pep4p-dependent vacuolar degradation of Ste6p. This study establishes that Ste6p is distinctive in that two independent degradative systems (the vacuolar Pep4p-dependent proteases and the cytosolic proteasome) are both involved, either directly or indirectly, in the metabolic degradation of a single substrate.

scholarly journals Ccr4 is a novel shuttle factor required for ubiquitin-dependent proteolysis by the 26S proteasome

2020 ◽  
Author(s):  
Ganapathi Kandasamy ◽  
Ashis Kumar Pradhan ◽  
R Palanimurugan
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Degradation ◽  
Ubiquitin Proteasome System ◽  
Proteasomal Degradation ◽  
Rna Degradation ◽  
26S Proteasome ◽  
Cellular Proteins ◽  
Cellular Homeostasis ◽  
Substrate Degradation ◽  
Ubiquitin Proteasome

AbstractDegradation of short-lived and abnormal proteins are essential for normal cellular homeostasis. In eukaryotes, such unstable cellular proteins are selectively degraded by the ubiquitin proteasome system (UPS). Furthermore, abnormalities in protein degradation by the UPS have been linked to several human diseases. Ccr4 protein is a known component of the Ccr4-Not complex, which has established roles in transcription, mRNA de-adenylation and RNA degradation etc. Excitingly in this study, we show that Ccr4 protein has a novel function as a shuttle factor that promotes ubiquitin-dependent degradation of short-lived proteins by the 26S proteasome. Using a substrate of the well-studied ubiquitin fusion degradation (UFD) pathway, we found that its UPS-mediated degradation was severely impaired upon deletion of CCR4 in Saccharomyces cerevisiae. Additionally, we show that Ccr4 binds to cellular ubiquitin conjugates and the proteasome. In contrast to Ccr4, most other subunits of the Ccr4-Not complex proteins are dispensable for UFD substrate degradation. From our findings we conclude that Ccr4 functions in the UPS as a shuttle factor targeting ubiquitylated substrates for proteasomal degradation.

scholarly journals ATP-dependent thermostabilization of human P-glycoprotein (ABCB1) is blocked by modulators

2019 ◽  
Vol 476 (24) ◽  
pp. 3737-3750 ◽  
Author(s):  
Sabrina Lusvarghi ◽  
Suresh V. Ambudkar
Keyword(s):  
Conformational Changes ◽  
Drug Transport ◽  
Atp Hydrolysis ◽  
Atp Binding ◽  
Dependent Manner ◽  
Deficient Mutant ◽  
Concentration Dependent Manner ◽  
Glycoprotein P ◽  
Binding Domains ◽  
P Glycoprotein

P-glycoprotein (P-gp), an ATP-binding cassette transporter associated with multidrug resistance in cancer cells, is capable of effluxing a number of xenobiotics as well as anticancer drugs. The transport of molecules through the transmembrane (TM) region of P-gp involves orchestrated conformational changes between inward-open and inward-closed forms, the details of which are still being worked out. Here, we assessed how the binding of transport substrates or modulators in the TM region and the binding of ATP to the nucleotide-binding domains (NBDs) affect the thermostability of P-gp in a membrane environment. P-gp stability after exposure at high temperatures (37–80°C) was assessed by measuring ATPase activity and loss of monomeric P-gp. Our results show that P-gp is significantly thermostabilized (>22°C higher IT50) by the binding of ATP under non-hydrolyzing conditions (in the absence of Mg2+). By using an ATP-binding-deficient mutant (Y401A) and a hydrolysis-deficient mutant (E556Q/E1201Q), we show that thermostabilization of P-gp requires binding of ATP to both NBDs and their dimerization. Additionally, we found that transport substrates do not affect the thermal stability of P-gp either in the absence or presence of ATP; in contrast, inhibitors of P-gp including tariquidar and zosuquidar prevent ATP-dependent thermostabilization in a concentration-dependent manner, by stabilizing the inward-open conformation. Altogether, our data suggest that modulators, which bind in the TM regions, inhibit ATP hydrolysis and drug transport by preventing the ATP-dependent dimerization of the NBDs of P-gp.

scholarly journals Involvement of Vesicle-Associated Membrane Protein 7 in Human Gastric Epithelial Cell Vacuolation Induced by Helicobacter pylori-Produced VacA

2008 ◽  
Vol 76 (6) ◽  
pp. 2296-2303 ◽  
Author(s):  
Hirosato Mashima ◽  
Junko Suzuki ◽  
Toshiya Hirayama ◽  
Yukako Yoshikumi ◽  
Hideki Ohno ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Membrane Protein ◽  
Intracellular Trafficking ◽  
Northern Blotting ◽  
Transient Transfection ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Dependent Manner ◽  
Snare Protein ◽  
Interfering Rna

ABSTRACT Helicobacter pylori-produced cytotoxin VacA induces intracellular vacuolation. The VacA-induced vacuole is assumed to represent the pathological status of intracellular trafficking. The fusion mechanism of the endosomes requires the formation of a tight complex between the Q-SNAREs and the R-SNAREs. We recently reported that syntaxin 7, a family member of the Q-SNARE protein, is involved in VacA-induced vacuole formation. In order to further elucidate the molecular mechanism, we identified the participation of vesicle-associated membrane protein 7 (VAMP7) as a partner of syntaxin 7. Immunocytochemistry revealed endogenous VAMP7 to be localized to the vacuoles induced by VacA. A Northern blotting study demonstrated that VacA intoxication increased VAMP7 mRNA in a time-dependent manner. VAMP7 was coimmunoprecipitated with syntaxin 7, and the amounts of endogenous VAMP7 and syntaxin 7 bound to syntaxin 7 and VAMP7, respectively, increased in response to VacA. The down-regulation of VAMP7 using small interfering RNA inhibited VacA-induced vacuolation, and the transient transfection of dominant-negative mutant VAMP7, the N-terminal domain of VAMP7, also inhibited the vacuolation. We therefore conclude that R-SNARE VAMP7 plays an important role in VacA-induced vacuolation as a partner of Q-SNARE syntaxin 7.

scholarly journals Sensitivity of Acute Myelocytic Leukemia Cells to the Dienone Compound VLX1570 Is Associated with Inhibition of the Ubiquitin-Proteasome System

Biomolecules ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1339
Author(s):  
Karthik Selvaraju ◽  
Kourosh Lotfi ◽  
Johannes Gubat ◽  
Maria Miquel ◽  
Amanda Nilsson ◽  
...  
Keyword(s):  
Cell Viability ◽  
Drug Exposure ◽  
Cancer Therapeutics ◽  
Ubiquitin Proteasome System ◽  
Glutathione Depletion ◽  
Acute Myelocytic Leukemia ◽  
Dependent Manner ◽  
Turnover Rates ◽  
Ubiquitin Proteasome

Dienone compounds with a 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore have been widely reported to show tumor cell selectivity. These compounds target the ubiquitin-proteasome system (UPS), known to be essential for the viability of tumor cells. The induction of oxidative stress, depletion of glutathione, and induction of high-molecular-weight (HMW) complexes have also been reported. We here examined the response of acute myeloid leukemia (AML) cells to the dienone compound VLX1570. AML cells have relatively high protein turnover rates and have also been reported to be sensitive to depletion of reduced glutathione. We found AML cells of diverse cytogenetic backgrounds to be sensitive to VLX1570, with drug exposure resulting in an accumulation of ubiquitin complexes, induction of ER stress, and the loss of cell viability in a dose-dependent manner. Caspase activation was observed but was not required for the loss of cell viability. Glutathione depletion was also observed but did not correlate to VLX1570 sensitivity. Formation of HMW complexes occurred at higher concentrations of VLX1570 than those required for the loss of cell viability and was not enhanced by glutathione depletion. To study the effect of VLX1570 we developed a zebrafish PDX model of AML and confirmed antigrowth activity in vivo. Our results show that VLX1570 induces UPS inhibition in AML cells and encourage further work in developing compounds useful for cancer therapeutics.

scholarly journals Exercise Training-Increased FBXO32 and FOXO1 in a Gender-Dependent Manner in Mild Cognitively Impaired African Americans: GEMS-1 Study

2021 ◽  
Vol 13 ◽  
Author(s):  
Fikru B. Bedada ◽  
Oyonumo E. Ntekim ◽  
Evaristus O. Nwulia ◽  
Thomas V. Fungwe ◽  
Sheeba Raaj Nadarajah ◽  
...  
Keyword(s):  
African Americans ◽  
Gene Expression Analysis ◽  
Ubiquitin Proteasome System ◽  
Cognitively Impaired ◽  
Dependent Manner ◽  
Specific Exercise ◽  
Ubiquitin Proteasome ◽  
The Brain ◽  
Gender Specific

The ubiquitin proteasome system (UPS) and FOXOs transcription factors play a pivotal role in cellular clearance and minimizing the accumulation of Aβ in neurodegeneration (ND). In African Americans (AAs) with mild cognitive impairment (MCI), the role of components of UPS and FOXOs; and whether they are amenable to exercise effects is unknown. We hypothesized that exercise can enhance cellular clearance systems during aging and ND by increasing expressions of FBXO32 and FOXO1. To test this hypothesis, we used TaqMan gene expression analysis in peripheral blood (PB) to investigate the component of UPS and FOXOs; and provide mechanistic insight at baseline, during exercise, and in both genders. At baseline, levels of FBXO32 were higher in women than in men. In our attempt to discern gender-specific exercise-related changes, we observed that levels of FBXO32 increased in men but not in women. Similarly, levels of FOXO1 increased in men only. These data suggest that a graded dose of FBXO32 and FOXO1 may be beneficial when PB cells carrying FBXO32 and FOXO1 summon into the brain in response to Alzheimer’s disease (AD) perturbation (docking station PB cells). Our observation is consistent with emerging studies that exercise allows the trafficking of blood factors. Given the significance of FBXO32 and FOXO1 to ND and associated muscle integrity, our findings may explain, at least in part, the benefits of exercise on memory, associated gait, and balance perturbation acknowledged to herald the emergence of MCI.

scholarly journals The Multispanning Membrane Protein Ste24p Catalyzes CAAXProteolysis and NH2-terminal Processing of the Yeast a-Factor Precursor

2001 ◽  
Vol 276 (50) ◽  
pp. 46798-46806 ◽  
Author(s):  
Amy Tam ◽  
Walter K. Schmidt ◽  
Susan Michaelis
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Membrane Protein ◽  
Proteolytic Activity ◽  
Dependent Manner ◽  
Mating Pheromone ◽  
Bona Fide

Saccharomyces cerevisiaeSte24p is a multispanning membrane protein implicated in the CAAXproteolysis step that occurs during biogenesis of the prenylated a-factor mating pheromone. Whether Ste24p acts directly as a CAAXprotease or indirectly to activate a downstream protease has not yet been established. In this study, we demonstrate that purified, detergent-solubilized Ste24p directly mediates CAAXproteolysis in a zinc-dependent manner. We also show that Ste24p mediates a separate proteolytic step, the first NH2-terminal cleavage in a-factor maturation. These results establish that Ste24p functions both as abona fideCOOH-terminal CAAXprotease and as an a-factor NH2-terminal protease. Importantly, this study is the first to directly demonstrate that a eukaryotic multispanning membrane protein can possess intrinsic proteolytic activity.

scholarly journals Sestrin2 Protects Dopaminergic Cells against Rotenone Toxicity through AMPK-Dependent Autophagy Activation

2015 ◽  
Vol 35 (16) ◽  
pp. 2740-2751 ◽  
Author(s):  
Yi-Sheng Hou ◽  
Jun-Jie Guan ◽  
Hai-Dong Xu ◽  
Feng Wu ◽  
Rui Sheng ◽  
...  
Keyword(s):  
Ubiquitin Proteasome System ◽  
Dependent Manner ◽  
Dopaminergic Cells ◽  
Protein Levels ◽  
Autophagy Induction ◽  
Ubiquitin Proteasome ◽  
Autophagic Degradation ◽  
Ampk Activity ◽  
Amp Activated Protein Kinase ◽  
Autophagy Activity

Dysfunction of the autophagy-lysosomal pathway (ALP) and the ubiquitin-proteasome system (UPS) was thought to be an important pathogenic mechanism in synuclein pathology and Parkinson's disease (PD). In the present study, we investigated the role of sestrin2 in autophagic degradation of α-synuclein and preservation of cell viability in a rotenone-induced cellular model of PD. We speculated that AMP-activated protein kinase (AMPK) was involved in regulation of autophagy and protection of dopaminergic cells against rotenone toxicity by sestrin2. The results showed that both the mRNA and protein levels of sestrin2 were increased in a TP53-dependent manner in Mes 23.5 cells after treatment with rotenone. Genetic knockdown of sestrin2 compromised the autophagy induction in response to rotenone, while overexpression of sestrin2 increased the basal autophagy activity. Sestrin2 presumably enhanced autophagy in an AMPK-dependent fashion, as sestrin2 overexpression activated AMPK, and genetic knockdown of AMPK abrogated autophagy induction by rotenone. Restoration of AMPK activity by metformin after sestrin2 knockdown recovered the autophagy activity. Sestrin2 overexpression ameliorated α-synuclein accumulation, inhibited caspase 3 activation, and reduced the cytotoxicity of rotenone. These results suggest that sestrin2 upregulation attempts to maintain autophagy activity and suppress rotenone cytotoxicity through activation of AMPK, and that sestrin2 exerts a protective effect on dopaminergic cells.

Chloroquine attenuates lipopolysaccharide-induced inflammatory responses through upregulation of USP25

2017 ◽  
Vol 95 (5) ◽  
pp. 481-491 ◽  
Author(s):  
Changyu Ding ◽  
Fangfang Li ◽  
Yupeng Long ◽  
Jiang Zheng
Keyword(s):  
Macrophage Activation ◽  
Nuclear Translocation ◽  
Inflammatory Responses ◽  
Ubiquitin Proteasome System ◽  
Mitogen Activated Protein Kinase ◽  
Dependent Manner ◽  
Activation Of Transcription ◽  
Tnf Α ◽  
Mitogen Activated Protein ◽  
Ubiquitin Proteasome

Lipopolysaccharide (LPS) is a key pathogenic factor in sepsis, and its recognition by toll-like receptor 4 (TLR4) can activate two district signaling pathways, leading to activation of transcription factors including NF-κB and interferon regulatory factor 3 (IRF3). Chloroquine (CQ) has been shown to affect LPS–TLR4 colocalization and inhibit both MyD88-dependent and TRAM/TRIF-dependent pathways, though the mechanism involved is still poorly understood. Here, we found that the ubiquitin–proteasome system might be involved in this process. CQ increased USP25, a deubiquitinating enzyme, as well as mRNA and protein expression in a dose-dependent manner, which might to some degree be involved in CQ attenuation of LPS-induced macrophage activation. Overexpression of USP25 decreased LPS-induced inflammatory cytokines like TNF-α, IL-6, and IFN-β, while specific siRNA-mediated USP25 silencing increased TNF-α, IL-6, and IFN-β production and secretion. In addition, USP25 deletion strengthened mitogen-activated protein kinase (MAPKs) phosphorylation and IκB degradation. Moreover, USP25 interference increased NF-κB and IRF3 nuclear translocation. Taken together, our data demonstrated a new possible regulator of LPS-induced macrophage activation mediated by CQ, through upregulation of USP25.

scholarly journals β-TrCP-mediated ubiquitination and degradation of Dlg5 regulates hepatocellular carcinoma cell proliferation

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Dongping Wang ◽  
Qi Zhang ◽  
Fenfen Li ◽  
Chan Wang ◽  
Changming Yang ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Xenograft Model ◽  
Ubiquitin Proteasome System ◽  
Tumor Xenograft ◽  
Dependent Manner ◽  
Ubiquitin Proteasome ◽  
Novel Strategy ◽  
Hcc Cells

Abstract Background Discs large homolog 5 (Dlg5) is a member of the membrane-associated guanylate kinase (MAGUK) adaptor family of proteins and its deregulation has been implicated in the malignancy of several cancer types. Dlg5 was down-regulated in hepatocellular carcinoma (HCC) and lower Dlg5 expression was associated with poor survival of HCC patients. However, how to regulate Dlg5 remains largely unknown. Methods The co-immunoprecipitation assay was used to determine the interaction between Dlg5 and β-TrCP. The in vivo ubiquitination assay was performed to determine the regulation of Dlg5 by β-TrCP. CCK-8 and colony formation assay were implemented to detect the biological effect of Dlg5 on the growth of HCC cells in vitro. The effect of Dlg5 on HCC tumor growth in vivo was studied in a tumor xenograft model in mice. Results Here we report that Dlg5 is regulated by the ubiquitin proteasome system and depletion of either Cullin 1 or β-TrCP led to increased levels of Dlg5. β-TrCP regulated Dlg5 protein stability by targeting it for ubiquitination and subsequent destruction in a phosphorylation-dependent manner. We further demonstrated a crucial role of Ser730 in the non-canonical phosphodegron of Dlg5 in governing β-TrCP-mediated Dlg5 degradation. Importantly, failure to degrade Dlg5 significantly inhibited HCC cells proliferation both in vitro and in vivo. Conclusion Collectively, our finding provides a novel molecular mechanism for the negative regulation of Dlg5 by β-TRCP in HCC cells. It further suggests that preventing Dlg5 degradation could be a possible novel strategy for clinical treatment of HCC.

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