scholarly journals A phosphoinositide-binding cluster in cavin1 acts as a molecular sensor for cavin1 degradation

2015 ◽  
Vol 26 (20) ◽  
pp. 3561-3569 ◽  
Author(s):  
Vikas A. Tillu ◽  
Oleksiy Kovtun ◽  
Kerrie-Ann McMahon ◽  
Brett M. Collins ◽  
Robert G. Parton
Keyword(s):  
Proteasomal Degradation ◽  
Resting Cells ◽  
Coat Proteins ◽  
Cellular Processes ◽  
Molecular Sensor ◽  
Lysine Residues ◽  
Low Levels ◽  
Membrane Stretching ◽  
Signaling Modules ◽  
Site Release

Caveolae are abundant surface organelles implicated in a range of cellular processes. Two classes of proteins work together to generate caveolae: integral membrane proteins termed caveolins and cytoplasmic coat proteins called cavins. Caveolae respond to membrane stress by releasing cavins into the cytosol. A crucial aspect of this model is tight regulation of cytosolic pools of cavin under resting conditions. We now show that a recently identified region of cavin1 that can bind phosphoinositide (PI) lipids is also a major site of ubiquitylation. Ubiquitylation of lysines within this site leads to rapid proteasomal degradation. In cells that lack caveolins and caveolae, cavin1 is cytosolic and rapidly degraded as compared with cells in which cavin1 is associated with caveolae. Membrane stretching causes caveolar disassembly, release of cavin complexes into the cytosol, and increased proteasomal degradation of wild-type cavin1 but not mutant cavin1 lacking the major ubiquitylation site. Release of cavin1 from caveolae thus leads to exposure of key lysine residues in the PI-binding region, acting as a trigger for cavin1 ubiquitylation and down-regulation. This mutually exclusive PI-binding/ubiquitylation mechanism may help maintain low levels of cytosolic cavin1 in resting cells, a prerequisite for cavins acting as signaling modules following release from caveolae.

scholarly journals Nuclear ERK: Mechanism of Translocation, Substrates, and Role in Cancer

2019 ◽  
Vol 20 (5) ◽  
pp. 1194 ◽  
Author(s):  
Galia Maik-Rachline ◽  
Avital Hacohen-Lev-Ran ◽  
Rony Seger
Keyword(s):  
Nuclear Translocation ◽  
Resting Cells ◽  
Nuclear Pores ◽  
Cellular Processes ◽  
Extracellular Signal ◽  
Anti Cancer ◽  
Proliferation And Differentiation ◽  
The One ◽  
Signaling Components ◽  
Proof Of Principle

The extracellular signal-regulated kinases 1/2 (ERK) are central signaling components that regulate stimulated cellular processes such as proliferation and differentiation. When dysregulated, these kinases participate in the induction and maintenance of various pathologies, primarily cancer. While ERK is localized in the cytoplasm of resting cells, many of its substrates are nuclear, and indeed, extracellular stimulation induces a rapid and robust nuclear translocation of ERK. Similarly to other signaling components that shuttle to the nucleus upon stimulation, ERK does not use the canonical importinmechanism of nuclear translocation. Rather, it has its own unique nuclear translocation signal (NTS) that interacts with importin7 to allow stimulated shuttling via the nuclear pores. Prevention of the nuclear translocation inhibits proliferation of B-Raf- and N/K-Ras-transformed cancers. This effect is distinct from the one achieved by catalytic Raf and MEK inhibitors used clinically, as cells treated with the translocation inhibitors develop resistance much more slowly. In this review, we describe the mechanism of ERK translocation, present all its nuclear substrates, discuss its role in cancer and compare its translocation to the translocation of other signaling components. We also present proof of principle data for the use of nuclear ERK translocation as an anti-cancer target. It is likely that the prevention of nuclear ERK translocation will eventually serve as a way to combat Ras and Raf transformed cancers with less side-effects than the currently used drugs.

Lysine modifications and autophagy

2012 ◽  
Vol 52 ◽  
pp. 65-77 ◽  
Author(s):  
Kristi L. Norris ◽  
Tso-Pang Yao
Keyword(s):  
Cellular Stress ◽  
Nutrient Deprivation ◽  
Substrate Selectivity ◽  
Catabolic Pathway ◽  
Post Translational Modifications ◽  
Cellular Processes ◽  
Lysine Residues ◽  
Clinical Potential ◽  
Insight Into

Nutrient deprivation or cellular stress leads to the activation of a catabolic pathway that is conserved across species, known as autophagy. This process is considered to be adaptive and plays an important role in a number of cellular processes, including metabolism, immunity and development. Autophagy has also been linked to diseases, such as cancer and neurodegeneration, highlighting the importance of a better insight into its regulation. In the present chapter, we discuss how PTMs (post-translational modifications) of lysine residues by acetylation and ubiquitination alter the function of key proteins involved in the activation, maturation and substrate selectivity of autophagy. We also discuss the clinical potential of targeting these modifications to modulate autophagic activities.

scholarly journals Numerous proteins with unique characteristics are degraded by the 26S proteasome following monoubiquitination

2016 ◽  
Vol 113 (32) ◽  
pp. E4639-E4647 ◽  
Author(s):  
Ori Braten ◽  
Ido Livneh ◽  
Tamar Ziv ◽  
Arie Admon ◽  
Izhak Kehat ◽  
...  
Keyword(s):  
Proteomic Analysis ◽  
Systematic Approach ◽  
Proteasomal Degradation ◽  
26S Proteasome ◽  
Yeast Cells ◽  
Wild Type ◽  
Polyubiquitin Chain ◽  
Cellular Processes

The “canonical” proteasomal degradation signal is a substrate-anchored polyubiquitin chain. However, a handful of proteins were shown to be targeted following monoubiquitination. In this study, we established—in both human and yeast cells—a systematic approach for the identification of monoubiquitination-dependent proteasomal substrates. The cellular wild-type polymerizable ubiquitin was replaced with ubiquitin that cannot form chains. Using proteomic analysis, we screened for substrates that are nevertheless degraded under these conditions compared with those that are stabilized, and therefore require polyubiquitination for their degradation. For randomly sampled representative substrates, we confirmed that their cellular stability is in agreement with our screening prediction. Importantly, the two groups display unique features: monoubiquitinated substrates are smaller than the polyubiquitinated ones, are enriched in specific pathways, and, in humans, are structurally less disordered. We suggest that monoubiquitination-dependent degradation is more widespread than assumed previously, and plays key roles in various cellular processes.

scholarly journals Core Glycosylation of Collagen Is Initiated by Two β(1-O)Galactosyltransferases

2008 ◽  
Vol 29 (4) ◽  
pp. 943-952 ◽  
Author(s):  
Belinda Schegg ◽  
Andreas J. Hülsmeier ◽  
Christoph Rutschmann ◽  
Charlotte Maag ◽  
Thierry Hennet
Keyword(s):  
Biological Significance ◽  
Protein Sequencing ◽  
Helix Formation ◽  
Left Handed ◽  
Hydroxy Proline ◽  
Mannose Binding ◽  
Triple Helix Formation ◽  
Lysine Residues ◽  
Low Levels ◽  
Binding Lectin

ABSTRACT Collagen is a trimer of three left-handed alpha chains representing repeats of the motif Gly-X-Y, where (hydroxy)proline and (hydroxy)lysine residues are often found at positions X and Y. Selected hydroxylysines are further modified by the addition of galactose and glucose-galactose units. Collagen glycosylation takes place in the endoplasmic reticulum before triple-helix formation and is mediated by β(1-O)galactosyl- and α(1-2)glucosyltransferase enzymes. We have identified two collagen galactosyltransferases using affinity chromatography and tandem mass spectrometry protein sequencing. The two collagen β(1-O)galactosyltransferases corresponded to the GLT25D1 and GLT25D2 proteins. Recombinant GLT25D1 and GLT25D2 enzymes showed a strong galactosyltransferase activity toward various types of collagen and toward the serum mannose-binding lectin MBL, which contains a collagen domain. Amino acid analysis of the products of GLT25D1 and GLT25D2 reactions confirmed the transfer of galactose to hydroxylysine residues. The GLT25D1 gene is constitutively expressed in human tissues, whereas the GLT25D2 gene is expressed only at low levels in the nervous system. The GLT25D1 and GLT25D2 enzymes are similar to CEECAM1, to which we could not attribute any collagen galactosyltransferase activity. The GLT25D1 and GLT25D2 genes now allow addressing of the biological significance of collagen glycosylation and the importance of this posttranslational modification in the etiology of connective tissue disorders.

scholarly journals Temporal Quantitative Phosphoproteomics Profiling of Interleukin-33 Signaling Network Reveals Unique Modulators of Monocyte Activation

Cells ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 138
Author(s):  
Devasahayam Arokia Balaya Rex ◽  
Yashwanth Subbannayya ◽  
Prashant Kumar Modi ◽  
Akhina Palollathil ◽  
Lathika Gopalakrishnan ◽  
...  
Keyword(s):  
Inflammatory Diseases ◽  
Leukocyte Adhesion ◽  
Cell Cycle Checkpoints ◽  
Mass Spectrometry Analysis ◽  
Dna Damage And Repair ◽  
Spectrometry Analysis ◽  
Interleukin 33 ◽  
Cellular Processes ◽  
Defensive Role ◽  
Signaling Modules

Interleukin-33 (IL-33), a member of the IL-1 superfamily cytokines, is an endogenous danger signal and a nuclear-associated cytokine. It is one of the essential mediators of both innate and adaptive immune responses. Aberrant IL-33 signaling has been demonstrated to play a defensive role against various infectious and inflammatory diseases. Although the signaling responses mediated by IL-33 have been previously reported, the temporal signaling dynamics are yet to be explored. To this end, we applied quantitative temporal phosphoproteomics analysis to elucidate pathways and proteins induced by IL-33 in THP-1 monocytes. Employing a TMT labeling-based quantitation and titanium dioxide (TiO2)-based phosphopeptide enrichment strategy followed by mass spectrometry analysis, we identified and quantified 9448 unique phosphopeptides corresponding to 3392 proteins that showed differential regulation. Of these, 171 protein kinases, 60 phosphatases and 178 transcription factors were regulated at different phases of IL-33 signaling. In addition to the confirmed activation of canonical signaling modules including MAPK, NFκB, PI3K/AKT modules, pathway analysis of the time-dependent phosphorylation dynamics revealed enrichment of several cellular processes, including leukocyte adhesion, response to reactive oxygen species, cell cycle checkpoints, DNA damage and repair pathways. The detailed quantitative phosphoproteomic map of IL-33 signaling will serve as a potentially useful resource to study its function in the context of inflammatory and pathological conditions.

scholarly journals Structural determinants and genetic modifications enhance BMP2 stability and extracellular secretion

2018 ◽  
Author(s):  
Vinayak Khattar ◽  
Joo Hyoung Lee ◽  
Hong Wang ◽  
Soniya Bastola ◽  
Selvarangan Ponnazhagan
Keyword(s):  
Half Life ◽  
Proteasomal Degradation ◽  
Structural Determinants ◽  
Extracellular Secretion ◽  
Short Half Life ◽  
Genetic Modifications ◽  
Lysine Residues ◽  
Stability Results ◽  
Enhanced Stability

ABSTRACTThe short half-life and use of recombinant bone morphogentic protein (BMP)-2 in large doses poses major limitations in the clinic. Events regulating post-translational processing and degradation of BMP2 in situ, linked to its secretion, have not been understood. Towards identifying mechanisms regulating intracellular BMP2 stability, we first discovered that inhibiting proteasomal degradation enhances both intracellular BMP2 level and its extracellular secretion. Next, we identified BMP2 degradation occurs through an ubiquitin-mediated mechanism. Since ubiquitination precedes proteasomal turnover and mainly occurs on lysine residues of nascent proteins, we systematically mutated individual lysine residues within BMP2 and tested them for enhanced stability. Results revealed that substitutions on four lysine residues within the pro-BMP2 region and three in the mature region increased both BMP2 turnover and extracellular secretion. Structural modeling revealed key lysine residues involved in proteasomal degradation occupy a lysine cluster near proprotein convertase cleavage site. Interestingly, mutations within these residues did not affect biological activity of BMP2. These data suggest preventing intracellular proteasomal loss of BMP2 through genetic modifications can overcome limitations related to its short half-life.

scholarly journals Post-translational regulation of ubiquitin signaling

2019 ◽  
Vol 218 (6) ◽  
pp. 1776-1786 ◽  
Author(s):  
Lei Song ◽  
Zhao-Qing Luo
Keyword(s):  
Translational Regulation ◽  
Covalent Attachment ◽  
Immune Disorders ◽  
Post Translational Modification ◽  
Polyubiquitin Chains ◽  
Cellular Processes ◽  
Lysine Residues ◽  
Substrate Proteins ◽  
Ubiquitination Machinery ◽  
Integrate Development

Ubiquitination regulates many essential cellular processes in eukaryotes. This post-translational modification (PTM) is typically achieved by E1, E2, and E3 enzymes that sequentially catalyze activation, conjugation, and ligation reactions, respectively, leading to covalent attachment of ubiquitin, usually to lysine residues of substrate proteins. Ubiquitin can also be successively linked to one of the seven lysine residues on ubiquitin to form distinctive forms of polyubiquitin chains, which, depending upon the lysine used and the length of the chains, dictate the fate of substrate proteins. Recent discoveries revealed that this ubiquitin code is further expanded by PTMs such as phosphorylation, acetylation, deamidation, and ADP-ribosylation, on ubiquitin, components of the ubiquitination machinery, or both. These PTMs provide additional regulatory nodes to integrate development or insulting signals with cellular homeostasis. Understanding the precise roles of these PTMs in the regulation of ubiquitin signaling will provide new insights into the mechanisms and treatment of various human diseases linked to ubiquitination, including neurodegenerative diseases, cancer, infection, and immune disorders.

scholarly journals Proteasomal degradation restricts the nuclear lifespan of AID

2008 ◽  
Vol 205 (6) ◽  
pp. 1357-1368 ◽  
Author(s):  
Said Aoufouchi ◽  
Ahmad Faili ◽  
Carole Zober ◽  
Orietta D'Orlando ◽  
Sandra Weller ◽  
...  
Keyword(s):  
Cell Line ◽  
Cytidine Deaminase ◽  
Proteasome Inhibitors ◽  
Proteasomal Degradation ◽  
Protein Accumulation ◽  
Restricted Form ◽  
Lysine Residues ◽  
Immunoglobulin Repertoire ◽  
The Stability ◽  
Specific Degradation

Activation-induced cytidine deaminase (AID) initiates all postrearrangement processes that diversify the immunoglobulin repertoire by specific deamination of cytidines at the immunoglobulin (Ig) locus. As uncontrolled expression of AID is potentially mutagenic, different types of regulation, particularly nucleocytoplasmic shuttling, restrict the likelihood of AID–deoxyribonucleic acid encounters. We studied additional mechanisms of regulation affecting the stability of the AID protein. No modulation of protein accumulation according to the cell cycle was observed in a Burkitt's lymphoma cell line. In contrast, the half-life of AID was markedly reduced in the nucleus, and this destabilization was accompanied by a polyubiquitination that was revealed in the presence of proteasome inhibitors. The same compartment-specific degradation was observed in activated mouse B cells, and also in a non–B cell line. No specific lysine residues could be linked to this degradation, so it remains unclear whether polyubiquitination proceeds through several alternatives sites or through the protein N terminus. The nuclear-restricted form of AID displayed enhanced mutagenicity at both Ig and non-Ig loci, most notably at TP53, suggesting that modulation of nuclear AID content through proteasomal degradation may represent another level of control of AID activity.

scholarly journals Human Cytomegalovirus Protein pp71 Induces Daxx SUMOylation

2009 ◽  
Vol 83 (13) ◽  
pp. 6591-6598 ◽  
Author(s):  
Jiwon Hwang ◽  
Robert F. Kalejta
Keyword(s):  
Gene Expression ◽  
Human Cytomegalovirus ◽  
Protein Function ◽  
Viral Infections ◽  
Biological Significance ◽  
Qualitative Change ◽  
Nuclear Bodies ◽  
Cellular Processes ◽  
Unknown Protein ◽  
Lysine Residues

ABSTRACT Proteins that participate in a diverse array of cellular processes can be modified covalently and reversibly on lysine residues by the small ubiquitin-like modifier proteins termed SUMOs. In some instances, such modification profoundly affects protein function, but the biological significance of many SUMOylation events remains unknown. Protein SUMOylation is modulated during many viral infections. Here we demonstrate that the human cytomegalovirus (HCMV) pp71 protein promotes the SUMOylation of its cellular substrate, Daxx. A component of promyelocytic leukemia nuclear bodies, Daxx is a transcriptional corepressor that silences the expression of viral immediate-early (IE) genes at the start of both lytic and quiescent HCMV infections. pp71 is a tegument component delivered directly to cells by infecting HCMV virions. At the start of lytic infections, it travels to the nucleus and stimulates viral IE gene expression by displacing the chromatin remodeling protein ATRX from Daxx and by mediating Daxx degradation through a rare ubiquitin-independent, proteasome-dependent process. Here we report that pp71 also substantially increases the basal level of SUMOylated Daxx observed in cells. To date, consequences of Daxx SUMOylation have not been observed for cellular promoters, and we detected no qualitative change in viral IE gene expression in the absence of pp71-induced Daxx SUMOylation. Thus, while pp71 enhances the basal level of SUMOylated Daxx, the role that this modification plays in regulating Daxx activity in uninfected or HCMV-infected cells remains an enigma.

scholarly journals The Hyperoxic-Hypoxic Paradox

Biomolecules ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 958 ◽  
Author(s):  
Amir Hadanny ◽  
Shai Efrati
Keyword(s):  
Cellular Level ◽  
Metabolic Changes ◽  
Regenerative Processes ◽  
Cellular Mechanisms ◽  
Absolute Level ◽  
Free Oxygen ◽  
Oxygen Levels ◽  
Cellular Processes ◽  
Low Levels ◽  
Oxygen Physiology

Effective metabolism is highly dependent on a narrow therapeutic range of oxygen. Accordingly, low levels of oxygen, or hypoxia, are one of the most powerful inducers of gene expression, metabolic changes, and regenerative processes, including angiogenesis and stimulation of stem cell proliferation, migration, and differentiation. The sensing of decreased oxygen levels (hypoxia) or increased oxygen levels (hyperoxia), occurs through specialized chemoreceptor cells and metabolic changes at the cellular level, which regulate the response. Interestingly, fluctuations in the free oxygen concentration rather than the absolute level of oxygen can be interpreted at the cellular level as a lack of oxygen. Thus, repeated intermittent hyperoxia can induce many of the mediators and cellular mechanisms that are usually induced during hypoxia. This is called the hyperoxic-hypoxic paradox (HHP). This article reviews oxygen physiology, the main cellular processes triggered by hypoxia, and the cascade of events triggered by the HHP.

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