Degradation Of Various Proteins Research Articles

CRBN-PROTACs in Cancer Therapy: From Mechanistic Insights to Clinical Applications.

Cereblon (CRBN), a member of the E3 ubiquitin ligase complex, has gained significant attention as a therapeutic target in cancer. CRBN regulates the degradation of various proteins in cancer progression, including transcription factors and signaling molecules. PROTACs (proteolysis-targeting chimeras) are a novel approach that uses the cell's degradation system to remove disease-causing proteins selectively. CRBN-dependent PROTACs work by tagging harmful proteins for destruction through the ubiquitin-proteasome system. This strategy offers several advantages over traditional protein inhibition methods, including the potential to overcome drug resistance. Recent progress in developing CRBN-based PROTACs has shown promising preclinical results in both hematologic malignancies and solid tumors. Additionally, CRBN-based PROTACs have enhanced our understanding of CRBN's role in cancer, potentially serving as biomarkers for patient stratification and predicting therapeutic responses. In this review, we delineate the mechanisms of action for CRBN-dependent PROTACs (CRBN-PROTACs), summarize recent advances in preclinical and clinical applications, and provide our perspective on future development.

SNX17 Mediates Dendritic Spine Maturation via p140Cap.

Sorting nexin17 (SNX17) is a member of the sorting nexin family, which plays a crucial role in endosomal trafficking. Previous research has shown that SNX17 is involved in the recycling or degradation of various proteins associated with neurodevelopmental and neurological diseases in cell models. However, the significance of SNX17 in neurological function in the mouse brain has not been thoroughly investigated. In this study, we generated Snx17 knockout mice and observed that the homozygous deletion of Snx17 (Snx17-/-) resulted in lethality. On the other hand, heterozygous mutant mice (Snx17+/-) exhibited anxiety-like behavior with a reduced preference for social novelty. Furthermore, Snx17 haploinsufficiency led to impaired synaptic transmission and reduced maturation of dendritic spines. Through GST pulldown and interactome analysis, we identified the SRC kinase inhibitor, p140Cap, as a potential downstream target of SNX17. We also demonstrated that the interaction between p140Cap and SNX17 is crucial for dendritic spine maturation. Together, this study provides the first in vivo evidence highlighting the important role of SNX17 in maintaining neuronal function, as well as regulating social novelty and anxiety-like behaviors.

Advances in the study of HSP70 inhibitors to enhance the sensitivity of tumor cells to radiotherapy.

The 70 kDa heat shock protein (HSP70) is one of the most conserved proteins and a ubiquitous molecular chaperone that plays a role in the folding, remodeling, and degradation of various proteins to maintain proteostasis. It has been shown that HSP70 is abundantly expressed in cancer and enhances tumor resistance to radiotherapy by inhibiting multiple apoptotic pathways, such as interfering with the cellular senescence program, promoting angiogenesis, and supporting metastasis. Thus, HSP70 provides an effective target for enhancing the effects of radiation therapy in the clinical management of cancer patients. Inhibition of HSP70 enhances the radiation-induced tumor-killing effect and thus improves the efficacy of radiotherapy. This article reviews the sensitivity of Hsp70 and its related inhibitors to radiotherapy of tumor cells.

The Role of the Mdm2/MdmX E3 Ligase System in Carcinogenesis, and Current Chemotherapeutic Interventions: A Literature Review

Introduction: E3 (ubiquitin) ligases play a major role in the ubiquitin-proteasome system (UPS), responsible for the ubiquitination and degradation of various proteins. The UPS has many roles, including regulation of the cell cycle. To mediate these functions, there are many different types of E3s, each with different substrates. A major E3 system involved in oncogenesis is the Mdm2/MdmX system, which acts as a heterodimer to degrade the tumour suppressor, p53, responsible for inducing cell cycle arrest and/or apoptosis in cancer cells, as needed. Upon overexpression/hyperactivation through mutation, the Mdm2/MdmX system can promote carcinogenesis through increasing degradation of p53, preventing necessary cell cycle arrest/apoptosis in cancer cells. Methods: A literature review was conducted to synthesize and analyze research on Mdm2/MdmX E3 overexpression/hyperactivation, and the treatment options available for cancers in which overexpression/hyperactivation plays a role. Results: There are many types of mutations that may be present in cancer cells, however mutations leading to the inactivation of p53 are some of the most common. Inactivation of p53 can be achieved by direct gene mutation, or overexpression/hyperactivation of Mdm2/Mdmx. Current drugs target the expression of MdmX/Mdm2 or their binding interactions with p53. Inhibition of these interactions triggers apoptosis in cancer cells due to increased p53 activity. Therapies that have been developed to target the Mdm2/MdmX system include small molecule inhibitors such as Nutlins and MI compounds, as well as peptide drugs. Discussion: Although direct mutations of p53 are commonly found in cancer, mutated p53 is not a viable drug target, so instead many treatment options specifically target a dysregulated Mdm2/MdmX system. Future studies should investigate novel drug targets, minimization of side effects, and treatment in the presence of mutations to other DNA repair systems. Conclusion: This literature review aids in establishing an interdisciplinary perspective on the types of oncogenic mutations in the Mdm2/MdmX pathway, combining biochemical and mechanistic research with clinical applications and pharmacology, as well as identifying future drug targets involved in this system.

FUNCTIONAL CHANGES IN THE CONCENTRATION OF TOTAL PROTEIN IN RESIDENTS OF THE KYZYLORDA REGION

Taking into account the ever-increasing role of prevention in modern conditions, a comprehensive understanding of the morph physiological and chronobiological organization of human life is necessary, which is most optimal for living in specific environmental conditions, in other words, the conditions for the formation of population health and its pathological deviations due to factors that exist in the very organism, as well as acting on it from the outside. The process of cleansing the body of denatured, aged proteins occurs in many organs, primarily in the liver. Degradation processes in a cell can both recognize proteins to be degraded and begin degradation, but these processes must be selective, since there is significant heterogeneity in the rates of degradation of various proteins in one cell. Proteases are usually required for the implementation of catabolic processes, and apparently, lysosomal and extra-lysosomal proteases are involved in the catabolism of cellular proteins. The concentration of total protein and its fractions in the blood plasma in people living in various districts of the Kyzylorda region does not depend on the severity of the action of extreme factors characteristic of the Aral Sea zone.

Auxin-mediated rapid degradation of target proteins in hippocampal neurons.

Genetic manipulation of protein levels is a promising approach to identify the function of a specific protein in living organisms. Previous studies demonstrated that the auxin-inducible degron strategy provides rapid and reversible degradation of various proteins in fungi and mammalian mitotic cells. In this study, we employed this technology to postmitotic neurons to address whether the auxin-inducible degron system could be applied to the nervous system. Using adeno-associated viruses, we simultaneously introduced enhanced green fluorescent protein (EGFP) fused with an auxin-inducible degron tag and an F-box family protein, TIR1 from Oryza sativa (OsTIR1), into hippocampal neurons from mice. In dissociated hippocampal neurons, EGFP enhanced green fluorescent protein fluorescence signals rapidly decreased when adding a plant hormone, auxin. Furthermore, auxin-induced enhanced green fluorescent protein degradation was also observed in hippocampal acute slices. Taken together, these results open the door for neuroscientists to manipulate protein expression levels by the auxin-inducible degron system in a temporally controlled manner.

Degradation of myofibrillar, sarcoplasmic and connective tissue proteins by plant proteolytic enzymes and their impact on camel meat tenderness.

Inside round muscles (Adductor) from camels treated with bromelain or ficin or papain at 50 or 100ppm were subsequently stored at 4°C for 4days to study the impact on quality attributes, protein degradation and textural changes. Results revealed that papain (100ppm) treated camel meat showed higher drip loss and lower water holding capacity compared to other treatments. Total protein, sarcoplasmic protein solubility, trichloroacetic acid (TCA)-soluble peptides and soluble collagen were higher in papain and bromelain treated samples at 100ppm compared to other treatments. Electrophoretic profile of whole camel meat, isolated sarcoplasmic and myofibrillar proteins depicted a noticeable degradation of various proteins in enzyme treated samples, with papain and bromelain (100ppm) displaying pronounced effect. Meat treated with papain at 100ppm displayed lower hardness and shear force (P < 0.05). Thus, enzymes treatment at 100ppm displayed good potential to tenderize camel meat with the papain being more effective among all.

Role of Mdm2 Cascade in Human Cancers

Mdm2 is a well known oncogene which affects expression of various genetic factors. It encoded oncoprotein Mdm2 of 491 amino acids divided into four major domains (p53-binding, acidic, Zn-finger and ring finger). Acting as an E3-ubiquitin ligase, Mdm2 induced degradation of various proteins which affect the cellular transformation such as p53, p73, JMY, FOXO3a, HPIP, HDAC, p21Waf1/CIP1 etc. Thus, Mdm2 found to be responsible for up and down regulation proteins in cellular system and plays crucial role in several human cancers through variety of biological pathways. Here, we described the major classes of human cancers in which Mdm2 involved directly or indirectly. Moreover, mechanistic role of Mdm2 summarised along with intermediates of cellular biochemical pathways regulated or expressed by it.

XLID CUL4B mutants are defective in promoting TSC2 degradation and positively regulating mTOR signaling in neocortical neurons

Truncating or missense mutation of cullin 4B (CUL4B) is one of the most prevalent causes underlying X-linked intellectual disability (XLID). CUL4B-RING E3 ubiquitin ligase promotes ubiquitination and degradation of various proteins. Consistent with previous studies, overexpression of wild-type CUL4B in 293 cells enhanced ubiquitylation and degradation of TSC2 or cyclin E. The present study shows that XLID mutant (R388X), (R572C) or (V745A) CULB failed to promote ubiquitination and degradation of TSC2 or cyclin E. Adenoviruses-mediated expression of wild-type CUL4B decreased protein level of TSC2 or cyclin E in cultured neocortical neurons of frontal lobe. Furthermore, shRNA-mediated CUL4B knockdown caused an upregulation of TSC2 or cyclin E. XLID mutant (R388X), (R572C) or (V745A) CUL4B did not downregulate protein expression of TSC2 or cyclin E in neocortical neurons. By promoting TSC2 degradation, CUL4B could positively regulate mTOR activity in neocortical neurons of frontal cortex. Consistent with this hypothesis, CUL4B knockdown-induced upregulation of TSC2 in neocortical neurons resulted in a decreased protein level of active phospho-mTORSer2448 and a reduced expression of active phospho-p70S6KThr389 and phospho-4E-BP1Thr37/46, two main substrates of mTOR-mediated phosphorylation. Wild-type CUL4B also increased protein level of active phospho-mTORSer2448, phospho-p70S6KThr389 or phospho-4E-BP1Thr37/46. XLID CUL4B mutants did not affect protein level of active phospho-mTORSer2448, phospho-p70S6KThr389 or phospho-4E-BP1Thr37/46. Our results suggest that XLID CUL4B mutants are defective in promoting TSC2 degradation and positively regulating mTOR signaling in neocortical neurons.

Altered neddylation in the heart of a mouse model for cardiomyopathy

We reported that a strain (4C30 strain) of mice with sialyltransferase (ST3GalII) transgenes would be a new mouse model for adult‐onset dilated cardiomyopathy (Proc Jpn Acad Ser B Phys Biol Sci. 2011; 87(8):550–562). Overexpression of ST3GalII perturbed protein glycosylation in 4C30 hearts, suggesting alteration of folding, translocation, and degradation of various proteins in 4C30 hearts. To study a possible involvement of protein degradation mechanisms in the cardiomyopathy, we compared neddylation statuses of heart proteins in our cardiomyopathic 4C30 mice with those in normal controls (C57BL/6NCr). Quantitative Western blots (QWB) for NEDD8 with GAPDH as a loading control revealed that two bands (100 and 105 kDa), but not four additional bands (90, 70, 60, or 40 KDa), were significantly denser in 4C30 hearts than in control hearts (p&lt;0.05). QWB for culins with GAPDH indicated that culin‐2, but not culin‐1 or ‐3, was significantly more abundant (p&lt;0.05). These results suggest that the protein degradation is altered in cardiomyopathic hearts.

βTrCP regulates BMI1 protein turnover via ubiquitination and degradation

The polycomb group protein BMI1 has been linked to proliferation, senescence, cancer progression and stem cell phenotype. At present, very little is known about its regulation. Here, we report that BMI1 contains a functional recognition motif for the F box protein βTrCP, which regulates ubiquitination and proteasome-mediated degradation of various proteins. We show that overexpression of wild-type βTrCP but not the ΔF mutant of it promotes BMI1 ubiquitination and degradation, and knockdown of βTrCP results in increased expression of BMI1. Furthermore, a mutant of BMI1 with an altered βTrCP recognition motif is much more stable than wild-type BMI1. We also show that wild-type BMI1 but not the mutant BMI1 interacts with βTrCP. Accordingly, compared to wild-type BMI1, mutant protein exhibited increased pro-oncogenic activity. In summary, our findings suggest that βTrCP regulates turnover of BMI1 and its function relevant to oncogenesis, cellular senescence and aging.

Ubiquilin 1 Modulates Amyloid Precursor Protein Trafficking and Aβ Secretion

Ubiquilin 1 (UBQLN1) is a ubiquitin-like protein, which has been shown to play a central role in regulating the proteasomal degradation of various proteins, including the presenilins. We recently reported that DNA variants in UBQLN1 increase the risk for Alzheimer disease, by influencing expression of this gene in brain. Here we present the first assessment of the effects of UBQLN1 on the metabolism of the amyloid precursor protein (APP). For this purpose, we employed RNA interference to down-regulate UBQLN1 in a variety of neuronal and non-neuronal cell lines. We demonstrate that down-regulation of UBQLN1 accelerates the maturation and intracellular trafficking of APP, while not interfering with alpha-, beta-, or gamma-secretase levels or activity. UBQLN1 knockdown increased the ratio of APP mature/immature, increased levels of full-length APP on the cell surface, and enhanced the secretion of sAPP (alpha- and beta-forms). Moreover, UBQLN1 knockdown increased levels of secreted Abeta40 and Abeta42. Finally, employing a fluorescence resonance energy transfer-based assay, we show that UBQLN1 and APP come into close proximity in intact cells, independently of the presence of the presenilins. Collectively, our findings suggest that UBQLN1 may normally serve as a cytoplasmic "gatekeeper" that may control APP trafficking from intracellular compartments to the cell surface. These findings suggest that changes in UBQLN1 steady-state levels affect APP trafficking and processing, thereby influencing the generation of Abeta.

Immunization with influenza A NP-expressing vaccinia virus recombinant protects mice against experimental infection with human and avian influenza viruses

Two-fold immunization of Balb/c mice with a vaccinia virus recombinant expressing the NP protein of influenza A/PR8/34 (H1N1) virus under the control of a strong synthetic promoter induced specific antibodies and protected animals against low-dose challenge by mouse-adapted heterosubtypic variants of human A/Aichi2/68 (H3N2) and avian A/Mallard/Pennsylvania/10218/84 (H5N2) influenza virus strains. The surviving immunized animals had lower anti-hemagglutinin antibody titers compared to non-immunized mice. There was no difference in viral titers in lungs of immunized and non-immunized animals that succumbed to the infection. In order to try to increase immune system presentation of NP-protein-derived peptides, and thereby increase their immunogenicity, we constructed another vaccinia-based NP-expressing recombinant containing a rapid proteolysis signal covalently bound to the NP protein. This sequence, derived from the mouse ornithine decarboxylase gene has been shown to increase degradation of various proteins. However, we found that when used as part of a recombinant NP, this signal neither increased its proteolytic degradation, nor was it more efficient in the induction of a protective response against influenza infection.

Hydrogen Peroxide-induced Structural Alterations of RNase A

Proteins exposed to oxidative stress are degraded via proteolytic pathways. In the present study, we undertook a series of in vitro experiments to establish a correlation between the structural changes induced by mild oxidation of the model protein RNase A and the proteolytic rate found upon exposure of the modified protein toward the isolated 20 S proteasome. Fourier transform infrared spectroscopy was used as a structure-sensitive probe. We report here strong experimental evidence for oxidation-induced conformational rearrangements of the model protein RNase A and, at the same time, for covalent modifications of amino acid side chains. Oxidation-related conformational changes, induced by H(2)O(2) exposure of the protein may be monitored in the amide I region, which is sensitive to changes in protein secondary structure. A comparison of the time- and H(2)O(2) concentration-dependent changes in the amide I region demonstrates a high degree of similarity to spectral alterations typical for temperature-induced unfolding of RNase A. In addition, spectral parameters of amino acid side chain marker bands (Tyr, Asp) revealed evidence for covalent modifications. Proteasome digestion measurements on oxidized RNase A revealed a specific time and H(2)O(2) concentration dependence; at low initial concentration of the oxidant, the RNase A turnover rate increases with incubation time and concentration. Based on these experimental findings, a correlation between structural alterations detected upon RNase A oxidation and proteolytic rates of RNase A is established, and possible mechanisms of the proteasome recognition process of oxidatively damaged proteins are discussed.

Cultured hepatoma cells as a model system for studying insulin processing and biologic responsiveness.

Monolayer cultures of minimal deviation hepatoma cells (H4-II-E-C3') bound and degraded insulin specifically, the apparent Ki value for insulin inhibition of both processes being 1 x 10(-8) M, indicating that cell-bound 125I-insulin is the substrate for subsequent hormone degradation in these cells as in isolated hepatocytes.1 The time course of insulin binding to its receptor depended on hormone concentration and temperature. Degradation of insulin also depended highly on temperature, with little or no degradation occurring at less than 20 degrees C, a temperature below which a membrane-lipid phase transition may block homone translocation or uptake. The effects of various agents on the binding and degradation of 125I-insulin also were tested. Agents believed to inhibit intralysosomal degradation of various proteins also inhibited the degradation of 125I-insulin by H4 cells (chloroquine, ammonium chloride, procaine, and lidocaine); inhibitors of energy production (dinitrophenol, sodium cyanide) inhibited degradation; an agent which inhibits microtubule function (vinblastine) blocked insulin degradation; and methylamine, reported to prevent receptor aggregation,2 also interfered with insulin processing. These findings are consistent with a model for cellular insulin processing, comprising receptor binding, clustering of receptors, endocytotic uptake, intralysosomal degradation, and extracellular release of some degradation products. H4 cells were highly sensitive to insulin. The KE for a half-maximal response of hormone-stimulated incorporationof 14C-glucose into glycogen was 10(-11) M insulin, corresponding to less than 1% receptor occupancy. This response was also mimicked by concanavalin A at a concentration of 10 microgram/ml. Vinblastine and chloroquine both significantly inhibited insulin-stimulated glucose incorporation into glycogen without affecting basal levels. However, since these inhibitory effects were not relieved by addition of excess insulin, it seems unlikely that their action on glycogen synthesis was exerted only at the level of the generation of an active intermediate or degradation product from hormone-receptor complexes. The hormone-sensitive H4 cells thus provide a useful system for further studies examining the role of insulin-receptor uptake in hormone action, receptor regulation, and signal termination.

Effect of glucose on plasma glucagon, growth hormone, and insulin in exchange transfusion.

<h3>Abstract</h3> Genetic manipulation of protein levels is a promising approach to identify the function of a specific protein in living organisms. Previous studies demonstrated that the auxin-inducible degron (AID) strategy provides rapid and reversible degradation of various proteins in fungi and mammalian mitotic cells. In this study, we employed this technology to postmitotic neurons to address whether the AID system could be applied to the nervous system. Using adeno-associated viruses, we simultaneously introduced EGFP fused with an AID tag, and an F-box family protein, TIR1 from <i>Oryza sativa</i> (OsTIR1) into hippocampal neurons. In dissociated hippocampal neurons, EGFP fluorescence signals rapidly decreased when adding a plant hormone, auxin. Further, auxin-induced EGFP degradation was also observed in hippocampal acute slices. Taken together, these results open the door for neuroscientists to manipulate protein expression levels by the AID-system in a temporally-controlled manner.