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MBio Jun 2024Merkel cell polyomavirus (MCPyV) is a double-stranded tumor virus that is the main causative agent of Merkel cell carcinoma (MCC). The MCPyV large T antigen (LT), an...
UNLABELLED
Merkel cell polyomavirus (MCPyV) is a double-stranded tumor virus that is the main causative agent of Merkel cell carcinoma (MCC). The MCPyV large T antigen (LT), an essential viral DNA replication protein, maintains viral persistence by interacting with host Skp1-Cullin 1-F-box (SCF) E3 ubiquitin ligase complexes, which subsequently induces LT's proteasomal degradation, restricting MCPyV DNA replication. SCF E3 ubiquitin ligases require their substrates to be phosphorylated to bind them, utilizing phosphorylated serine residues as docking sites. The MCPyV LT unique region (MUR) is highly phosphorylated and plays a role in multiple host protein interactions, including SCF E3 ubiquitin ligases. Therefore, this domain highly governs LT stability. Though much work has been conducted to identify host factors that restrict MCPyV LT protein expression, the kinase(s) that cooperates with the SCF E3 ligase remains unknown. Here, we demonstrate that casein kinase 1 alpha (CK1α) negatively regulates MCPyV LT stability and LT-mediated replication by modulating interactions with the SCF β-TrCP. Specifically, we show that numerous CK1 isoforms (α, δ, ε) localize in close proximity to MCPyV LT through proximity ligation assays (PLA) and CK1α overexpression mainly resulted in decreased MCPyV LT protein expression. Inhibition of CK1α using short hairpin RNA (shRNA) and treatment of a CK1α inhibitor or an mTOR inhibitor, TORKinib, resulted in decreased β-TrCP interaction with LT, increased LT expression, and enhanced MCPyV replication. The expression level of the gene transcripts is higher in MCPyV-positive MCC, suggesting a vital role of CK1α in limiting MCPyV replication required for establishing persistent infection.
IMPORTANCE
Merkel cell polyomavirus (MCPyV) large tumor antigen is a polyphosphoprotein and the phosphorylation event is required to modulate various functions of LT, including viral replication. Therefore, cellular kinase pathways are indispensable for governing MCPyV polyomavirus infection and life cycle in coordinating with the immunosuppression environment at disease onset. Understanding the regulation mechanisms of MCPyV replication by viral and cellular factors will guide proper prevention strategies with targeted inhibitors for MCPyV-associated Merkel cell carcinoma (MCC) patients, who currently lack therapies.
PubMed: 38940554
DOI: 10.1128/mbio.01117-24 -
Advanced Science (Weinheim,... Jun 2024Retention of metabolic end-products in the bodily fluids of patients with chronic kidney disease (CKD) may lead to uremia. The uremic toxin indoxyl sulfate (IS), a...
Retention of metabolic end-products in the bodily fluids of patients with chronic kidney disease (CKD) may lead to uremia. The uremic toxin indoxyl sulfate (IS), a tryptophan metabolite, is an endogenous ligand of aryl hydrocarbon receptor (AhR). It is clarified that the upregulation and activation of AhR by IS in tubular epithelial cells (TECs) promote renal senescence and fibrosis. Renal TEC-specific knockout of AhR attenuates renal senescence and fibrosis, as well as the suppression of PGC1α-mediated mitochondrial biogenesis in ischemia reperfusion (IR)- or IS-treated CKD mice kidneys. Overexpression of peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC1α) attenuates IS-induced cell senescence and extracellular matrix production in cultured TECs. Mechanistically, AhR is able to interact with PGC1α and promotes the ubiquitin degradation of PGC1α via its E3 ubiquitin ligase activity. In summary, the elevation and activation of AhR by the accumulated uremic toxins in the progression of CKD accelerate renal senescence and fibrosis by suppressing mitochondrial biogenesis via promoting ubiquitination and proteasomal degradation of PGC1α.
PubMed: 38940381
DOI: 10.1002/advs.202402066 -
International Journal of Molecular... Aug 2024The ubiquitin (Ub)‑proteasome system (UPS) plays a pivotal role in maintaining protein homeostasis and function to modulate various cellular processes including... (Review)
Review
The ubiquitin (Ub)‑proteasome system (UPS) plays a pivotal role in maintaining protein homeostasis and function to modulate various cellular processes including skeletal cell differentiation and bone homeostasis. The Ub ligase E3 promotes the transfer of Ub to the target protein, especially transcription factors, to regulate the proliferation, differentiation and survival of bone cells, as well as bone formation. In turn, the deubiquitinating enzyme removes Ub from modified substrate proteins to orchestrate bone remodeling. As a result of abnormal regulation of ubiquitination, bone cell differentiation exhibits disorder and then bone homeostasis is affected, consequently leading to osteoporosis. The present review discussed the role and mechanism of UPS in bone remodeling. However, the specific mechanism of UPS in the process of bone remodeling is still not fully understood and further research is required. The study of the mechanism of action of UPS can provide new ideas and methods for the prevention and treatment of osteoporosis. In addition, the most commonly used osteoporosis drugs that target ubiquitination processes in the clinic are discussed in the current review.
Topics: Humans; Osteoporosis; Ubiquitination; Animals; Ubiquitin; Proteasome Endopeptidase Complex; Bone Remodeling; Ubiquitin-Protein Ligases
PubMed: 38940355
DOI: 10.3892/ijmm.2024.5392 -
Biomeditsinskaia Khimiia Jun 2024Renalase (RNLS) is a recently discovered protein that plays an important role in the regulation of blood pressure by acting inside and outside cells. Intracellular RNLS...
Renalase (RNLS) is a recently discovered protein that plays an important role in the regulation of blood pressure by acting inside and outside cells. Intracellular RNLS is a FAD-dependent oxidoreductase that oxidizes isomeric forms of β-NAD(P)H. Extracellular renalase lacking its N-terminal peptide and cofactor FAD exerts various protective effects via non-catalytic mechanisms. Certain experimental evidence exists in the literature that the RP220 peptide (a 20-mer peptide corresponding to the amino acid sequence RNLS 220-239) reproduces a number of non-catalytic effects of this protein, acting on receptor proteins of the plasma membrane. The possibility of interaction of this peptide with intracellular proteins has not been studied. Taking into consideration the known role of RNLS as a possible antihypertensive factor, the aim of this study was to perform proteomic profiling of the kidneys of normotensive and hypertensive rats using RP220 as an affinity ligand. Proteomic (semi-quantitative) identification revealed changes in the relative content of about 200 individual proteins in the kidneys of hypertensive rats bound to the affinity sorbent as compared to the kidneys of normotensive animals. Increased binding of SHR renal proteins to RP220 over the normotensive control was found for proteins involved in the development of cardiovascular pathology. Decreased binding of the kidney proteins from hypertensive animals to RP220 was noted for components of the ubiquitin-proteasome system, ribosomes, and cytoskeleton.
Topics: Animals; Rats; Kidney; Hypertension; Rats, Inbred SHR; Proteomics; Monoamine Oxidase; Male; Ligands; Peptides; Proteome
PubMed: 38940203
DOI: 10.18097/PBMC20247003145 -
Current Medicinal Chemistry Jun 2024Tripartite-motif protein family member 65 (TRIM65) belongs to the tripartite motif (TRIM) protein family. Its typical structure consists of the RING, B-Box motif, and...
Tripartite-motif protein family member 65 (TRIM65) belongs to the tripartite motif (TRIM) protein family. Its typical structure consists of the RING, B-Box motif, and coiled-coil domains, which are highly conserved at the N-terminus and the variable SPRY domain at the C-terminus. TRIM65 is an E3 ubiquitin ligase that participates in physiological and pathological processes through the ubiquitination pathway, including intracellular signal transduction, protein degradation, cell proliferation, apoptosis, carcinogenesis, autophagy, and phenotypic transformation. Evidence shows that TRIM65 plays a remarkable and obscure role in diseases, including multisystem tumours, neurodegenerative diseases, immune system diseases, and inflammatory diseases. This review is devoted to elaborating on the relationship between TRIM65 and diseases and its pathogenic mechanism, providing a theoretical basis for TRIM65 as a possible pathogenic target of diseases and exploring the possible future research direction of TRIM65 and the challenges it may face.
PubMed: 38939997
DOI: 10.2174/0109298673304966240614091547 -
Frontiers in Immunology 2024TRIM21 is a pivotal effector in the immune system, orchestrating antibody-mediated responses and modulating immune signaling. In this comprehensive study, we focus on...
TRIM21 is a pivotal effector in the immune system, orchestrating antibody-mediated responses and modulating immune signaling. In this comprehensive study, we focus on the interaction of TRIM21 with Fc engineered antibodies and subsequent implications for viral neutralization. Through a series of analytical techniques, including biosensor assays, mass photometry, and electron microscopy, along with structure predictions, we unravel the intricate mechanisms governing the interplay between TRIM21 and antibodies. Our investigations reveal that the TRIM21 capacity to recognize, bind, and facilitate the proteasomal degradation of antibody-coated viruses is critically dependent on the affinity and avidity interplay of its interactions with antibody Fc regions. We suggest a novel binding mechanism, where TRIM21 binding to one Fc site results in the detachment of PRYSPRY from the coiled-coil domain, enhancing mobility due to its flexible linker, thereby facilitating the engagement of the second site, resulting in avidity due to bivalent engagement. These findings shed light on the dual role of TRIM21 in antiviral immunity, both in recognizing and directing viruses for intracellular degradation, and demonstrate its potential for therapeutic exploitation. The study advances our understanding of intracellular immune responses and opens new avenues for the development of antiviral strategies and innovation in tailored effector functions designed to leverage TRIM21s unique binding mode.
Topics: Humans; Ribonucleoproteins; Protein Binding; Antibodies, Neutralizing; Immunoglobulin Fc Fragments; Protein Engineering; Antibodies, Viral; Antibody Affinity; Animals
PubMed: 38938560
DOI: 10.3389/fimmu.2024.1401471 -
MedComm Jul 2024Targeting the programmed cell death 1/programmed cell death ligand 1 (PD-1/PD-L1) pathway has been identified as a successful approach for tumor immunotherapy. Here, we...
Targeting the programmed cell death 1/programmed cell death ligand 1 (PD-1/PD-L1) pathway has been identified as a successful approach for tumor immunotherapy. Here, we identified that the small molecule 5,7,4'-trimethoxyflavone (TF) from Wall reduces PD-L1 expression in colorectal cancer cells and enhances the killing of tumor cells by T cells. Mechanistically, TF targets and stabilizes the ubiquitin ligase HMG-CoA reductase degradation protein 1 (HRD1), thereby increasing the ubiquitination of PD-L1 and promoting its degradation through the proteasome pathway. In mouse MC38 xenograft tumors, TF can activate tumor-infiltrating T-cell immunity and reduce the immunosuppressive infiltration of myeloid-derived suppressor cells and regulatory T cells, thus exerting antitumor effects. Moreover, TF synergistically exerts antitumor immunity with CTLA-4 antibody. This study provides new insights into the antitumor mechanism of TF and suggests that it may be a promising small molecule immune checkpoint modulator for cancer therapy.
PubMed: 38938284
DOI: 10.1002/mco2.611 -
Signal Transduction and Targeted Therapy Jun 2024The ORF9b protein, derived from the nucleocapsid's open-reading frame in both SARS-CoV and SARS-CoV-2, serves as an accessory protein crucial for viral immune evasion by...
The ORF9b protein, derived from the nucleocapsid's open-reading frame in both SARS-CoV and SARS-CoV-2, serves as an accessory protein crucial for viral immune evasion by inhibiting the innate immune response. Despite its significance, the precise regulatory mechanisms underlying its function remain elusive. In the present study, we unveil that the ORF9b protein of SARS-CoV-2, including emerging mutant strains like Delta and Omicron, can undergo ubiquitination at the K67 site and subsequent degradation via the proteasome pathway, despite certain mutations present among these strains. Moreover, our investigation further uncovers the pivotal role of the translocase of the outer mitochondrial membrane 70 (TOM70) as a substrate receptor, bridging ORF9b with heat shock protein 90 alpha (HSP90α) and Cullin 5 (CUL5) to form a complex. Within this complex, CUL5 triggers the ubiquitination and degradation of ORF9b, acting as a host antiviral factor, while HSP90α functions to stabilize it. Notably, treatment with HSP90 inhibitors such as GA or 17-AAG accelerates the degradation of ORF9b, leading to a pronounced inhibition of SARS-CoV-2 replication. Single-cell sequencing data revealed an up-regulation of HSP90α in lung epithelial cells from COVID-19 patients, suggesting a potential mechanism by which SARS-CoV-2 may exploit HSP90α to evade the host immunity. Our study identifies the CUL5-TOM70-HSP90α complex as a critical regulator of ORF9b protein stability, shedding light on the intricate host-virus immune response dynamics and offering promising avenues for drug development against SARS-CoV-2 in clinical settings.
Topics: Humans; Cullin Proteins; SARS-CoV-2; Virus Replication; HSP90 Heat-Shock Proteins; COVID-19; Ubiquitination; HEK293 Cells; Benzoquinones; Protein Stability; Vero Cells; Viral Proteins; Lactams, Macrocyclic
PubMed: 38937432
DOI: 10.1038/s41392-024-01874-5 -
Journal of Controlled Release :... Jun 2024Heterobifunctional small molecule degraders are a subset of targeted protein degraders (TPDs), consisting of two ligands joined by a linker to induce proteasomal... (Review)
Review
Heterobifunctional small molecule degraders are a subset of targeted protein degraders (TPDs), consisting of two ligands joined by a linker to induce proteasomal degradation of a target protein. As compared to traditional small molecules these compounds generally demonstrate inflated physicochemical properties, which may require innovative formulation strategies to enable their delivery and exert pharmacodynamic effect. The blood brain barrier (BBB) serves an essential function in human physiology, but its presence requires advanced approaches for treating central nervous system (CNS) diseases. By integrating emerging modalities like TPDs with conventional concepts of drug delivery, novel strategies to overcome the BBB can be developed. Amongst the available routes, lipid and polymer-based long-acting delivery seems to be the most amenable to TPDs, due to their ability to encapsulate lipophilic cargo and potential to be functionalized for targeted delivery. Another key consideration will be understanding E3 ligase expression in the different regions of the brain. Discovery of new brain or CNS disease specific E3 ligases could help overcome some of the barriers currently associated with CNS delivery of TPDs. This review discusses the current strategies that exist to overcome and improve therapeutic delivery of TPDs to the CNS.
PubMed: 38936742
DOI: 10.1016/j.jconrel.2024.06.057 -
Journal of Plant Physiology Jun 2024The F-box protein (FBP) family plays diverse functions in the plant kingdom, with the function of many members still unrevealed. In this study, a specific FBP called...
The F-box protein (FBP) family plays diverse functions in the plant kingdom, with the function of many members still unrevealed. In this study, a specific FBP called PmFBK2, containing Kelch repeats from Persicaria minor, was functionally investigated. Employing the yeast two-hybrid (Y2H) assay, PmFBK2 was found to interact with Skp1-like proteins from P. minor, suggesting its potential to form an E3 ubiquitin ligase, known as the SCF complex. Y2H and co-immunoprecipitation tests revealed that PmFBK2 interacts with full-length PmGID1b. The interaction marks the first documented binding between these two protein types, which have never been reported in other plants before, and they exhibited a negative effect on gibberellin (GA) signal transduction. The overexpression of PmFBK2 in the kmd3 mutant, a homolog from Arabidopsis, demonstrated the ability of PmFBK2 to restore the function of the mutated KMD3 gene. The function restoration was supported by morphophysiological and gene expression analyses, which exhibited patterns similar to the wild type (WT) compared to the kmd3 mutant. Interestingly, the overexpression of PmFBK2 or PmGID1b in Arabidopsis had opposite effects on rosette diameter, seed weight, and plant height. This study provides new insights into the complex GA signalling. It highlights the crucial roles of the interaction between FBP and the GA receptor (GID1b) in regulating GA responses. These findings have implications for developing strategies to enhance plant growth and yield by modulating GA signalling in crops.
PubMed: 38936241
DOI: 10.1016/j.jplph.2024.154299