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1.
Protein Sci ; 33(6): e4996, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38747383

RESUMO

The Sec61 translocon allows the translocation of secretory preproteins from the cytosol to the endoplasmic reticulum lumen during polypeptide biosynthesis. These proteins possess an N-terminal signal peptide (SP) which docks at the translocon. SP mutations can abolish translocation and cause diseases, suggesting an essential role for this SP/Sec61 interaction. However, a detailed biophysical characterization of this binding is still missing. Here, optical tweezers force spectroscopy was used to characterize the kinetic parameters of the dissociation process between Sec61 and the SP of prepro-alpha-factor. The unbinding parameters including off-rate constant and distance to the transition state were obtained by fitting rupture force data to Dudko-Hummer-Szabo models. Interestingly, the translocation inhibitor mycolactone increases the off-rate and accelerates the SP/Sec61 dissociation, while also weakening the interaction. Whereas the translocation deficient mutant containing a single point mutation in the SP abolished the specificity of the SP/Sec61 binding, resulting in an unstable interaction. In conclusion, we characterize quantitatively the dissociation process between the signal peptide and the translocon, and how the unbinding parameters are modified by a translocation inhibitor.


Assuntos
Pinças Ópticas , Canais de Translocação SEC , Canais de Translocação SEC/metabolismo , Canais de Translocação SEC/química , Canais de Translocação SEC/genética , Sinais Direcionadores de Proteínas , Ligação Proteica , Transporte Proteico , Cinética
2.
Sci Rep ; 14(1): 9506, 2024 04 25.
Artigo em Inglês | MEDLINE | ID: mdl-38664472

RESUMO

SEC61A1 encodes a central protein of the mammalian translocon and dysfunction results in severe disease. Recently, mutation R236C was identified in patients having autosomal dominant polycystic liver disease (ADPLD). The molecular phenotype of R236C was assessed in two cellular platforms. Cells were immortalized by retroviral transduction of an oncogene (UCi) or reprogrammed to induced pluripotent stem cells (iPSC) that were differentiated to cholangiocyte progenitor-like cells (CPLC). UCi and CPLC were subjected to analyses of molecular pathways that were associated with development of disease. UCi displayed markers of epithelial cells, while CPLCs expressed typical markers of both cholangiocytes and hepatocytes. Cells encoding R236C showed a stable, continuous proliferation in both platforms, however growth rates were reduced as compared to wildtype control. Autophagy, cAMP synthesis, and secretion of important marker proteins were reduced in R236C-expressing cells. In addition, R236C induced increased calcium leakiness from the ER to the cytoplasm. Upon oxidative stress, R236C led to a high induction of apoptosis and necrosis. Although the grade of aberrant cellular functions differed between the two platforms, the molecular phenotype of R236C was shared suggesting that the mutation, regardless of the cell type, has a dominant impact on disease-associated pathways.


Assuntos
Células-Tronco Pluripotentes Induzidas , Canais de Translocação SEC , Canais de Translocação SEC/metabolismo , Canais de Translocação SEC/genética , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Diferenciação Celular , Autofagia/genética , Mutação , Hepatócitos/metabolismo , Apoptose/genética , Estresse Oxidativo , Proliferação de Células
3.
Cells ; 13(5)2024 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-38474341

RESUMO

SecA is a widely conserved ATPase that drives the secretion of proteins across the cell membrane via the SecYEG translocon, while the SRP system is a key player in the insertion of membrane proteins via SecYEG. How SecA gains access to substrate proteins in Bacillus subtilis cells and copes with an increase in substrate availability during biotechnologically desired, high-level expression of secreted proteins is poorly understood. Using single molecule tracking, we found that SecA localization closely mimics that of ribosomes, and its molecule dynamics change similarly to those of ribosomes after inhibition of transcription or translation. These data suggest that B. subtilis SecA associates with signal peptides as they are synthesized at the ribosome, similar to the SRP system. In agreement with this, SecA is a largely mobile cytosolic protein; only a subset is statically associated with the cell membrane, i.e., likely with the Sec translocon. SecA dynamics were considerably different during the late exponential, transition, and stationary growth phases, revealing that single molecule dynamics considerably alter during different genetic programs in cells. During overproduction of a secretory protein, AmyE, SecA showed the strongest changes during the transition phase, i.e., where general protein secretion is high. To investigate whether the overproduction of AmyE also has an influence on other proteins that interact with SecYEG, we analyzed the dynamics of SecDF, YidC, and FtsY with and without AmyE overproduction. SecDF and YidC did not reveal considerable differences in single molecule dynamics during overexpression, while the SRP component FtsY changed markedly in its behavior and became more statically engaged. These findings indicate that the SRP pathway becomes involved in protein secretion upon an overload of proteins carrying a signal sequence. Thus, our data reveal high plasticity of the SecA and SRP systems in dealing with different needs for protein secretion.


Assuntos
Proteínas de Escherichia coli , Proteínas de Membrana Transportadoras , Proteínas de Membrana Transportadoras/metabolismo , Proteínas de Escherichia coli/genética , Bacillus subtilis/metabolismo , Proteínas de Bactérias/metabolismo , Proteínas de Membrana/metabolismo , Canais de Translocação SEC/metabolismo
4.
Nature ; 627(8003): 437-444, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38383789

RESUMO

Stalled ribosomes at the endoplasmic reticulum (ER) are covalently modified with the ubiquitin-like protein UFM1 on the 60S ribosomal subunit protein RPL26 (also known as uL24)1,2. This modification, which is known as UFMylation, is orchestrated by the UFM1 ribosome E3 ligase (UREL) complex, comprising UFL1, UFBP1 and CDK5RAP3 (ref. 3). However, the catalytic mechanism of UREL and the functional consequences of UFMylation are unclear. Here we present cryo-electron microscopy structures of UREL bound to 60S ribosomes, revealing the basis of its substrate specificity. UREL wraps around the 60S subunit to form a C-shaped clamp architecture that blocks the tRNA-binding sites at one end, and the peptide exit tunnel at the other. A UFL1 loop inserts into and remodels the peptidyl transferase centre. These features of UREL suggest a crucial function for UFMylation in the release and recycling of stalled or terminated ribosomes from the ER membrane. In the absence of functional UREL, 60S-SEC61 translocon complexes accumulate at the ER membrane, demonstrating that UFMylation is necessary for releasing SEC61 from 60S subunits. Notably, this release is facilitated by a functional switch of UREL from a 'writer' to a 'reader' module that recognizes its product-UFMylated 60S ribosomes. Collectively, we identify a fundamental role for UREL in dissociating 60S subunits from the SEC61 translocon and the basis for UFMylation in regulating protein homeostasis at the ER.


Assuntos
Retículo Endoplasmático , Processamento de Proteína Pós-Traducional , Subunidades Ribossômicas Maiores de Eucariotos , Ubiquitina-Proteína Ligases , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Sítios de Ligação , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/ultraestrutura , Microscopia Crioeletrônica , Retículo Endoplasmático/metabolismo , Retículo Endoplasmático/ultraestrutura , Homeostase , Membranas Intracelulares/metabolismo , Peptidil Transferases/química , Peptidil Transferases/metabolismo , Peptidil Transferases/ultraestrutura , Proteínas Ribossômicas/química , Proteínas Ribossômicas/metabolismo , Proteínas Ribossômicas/ultraestrutura , RNA de Transferência/metabolismo , Canais de Translocação SEC/química , Canais de Translocação SEC/metabolismo , Canais de Translocação SEC/ultraestrutura , Proteínas Supressoras de Tumor/química , Proteínas Supressoras de Tumor/metabolismo , Proteínas Supressoras de Tumor/ultraestrutura , Ubiquitina-Proteína Ligases/química , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina-Proteína Ligases/ultraestrutura , Subunidades Ribossômicas Maiores de Eucariotos/química , Subunidades Ribossômicas Maiores de Eucariotos/metabolismo , Subunidades Ribossômicas Maiores de Eucariotos/ultraestrutura
5.
EMBO J ; 43(1): 1-13, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38177311

RESUMO

The Sec translocon is a highly conserved membrane assembly for polypeptide transport across, or into, lipid bilayers. In bacteria, secretion through the core channel complex-SecYEG in the inner membrane-is powered by the cytosolic ATPase SecA. Here, we use single-molecule fluorescence to interrogate the conformational state of SecYEG throughout the ATP hydrolysis cycle of SecA. We show that the SecYEG channel fluctuations between open and closed states are much faster (~20-fold during translocation) than ATP turnover, and that the nucleotide status of SecA modulates the rates of opening and closure. The SecY variant PrlA4, which exhibits faster transport but unaffected ATPase rates, increases the dwell time in the open state, facilitating pre-protein diffusion through the pore and thereby enhancing translocation efficiency. Thus, rapid SecYEG channel dynamics are allosterically coupled to SecA via modulation of the energy landscape, and play an integral part in protein transport. Loose coupling of ATP-turnover by SecA to the dynamic properties of SecYEG is compatible with a Brownian-rachet mechanism of translocation, rather than strict nucleotide-dependent interconversion between different static states of a power stroke.


Assuntos
Proteínas de Bactérias , Proteínas de Escherichia coli , Canais de Translocação SEC/química , Proteínas SecA/metabolismo , Proteínas de Bactérias/metabolismo , Adenosina Trifosfatases/genética , Adenosina Trifosfatases/metabolismo , Transporte Proteico , Nucleotídeos/metabolismo , Trifosfato de Adenosina/metabolismo , Proteínas de Escherichia coli/metabolismo
6.
EMBO Rep ; 24(12): e57910, 2023 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-37983950

RESUMO

Protein translocation across the endoplasmic reticulum (ER) membrane is an essential step during protein entry into the secretory pathway. The conserved Sec61 protein-conducting channel facilitates polypeptide translocation and coordinates cotranslational polypeptide-processing events. In cells, the majority of Sec61 is stably associated with a heterotetrameric membrane protein complex, the translocon-associated protein complex (TRAP), yet the mechanism by which TRAP assists in polypeptide translocation remains unknown. Here, we present the structure of the core Sec61/TRAP complex bound to a mammalian ribosome by cryogenic electron microscopy (cryo-EM). Ribosome interactions anchor the Sec61/TRAP complex in a conformation that renders the ER membrane locally thinner by significantly curving its lumenal leaflet. We propose that TRAP stabilizes the ribosome exit tunnel to assist nascent polypeptide insertion through Sec61 and provides a ratcheting mechanism into the ER lumen mediated by direct polypeptide interactions.


Assuntos
Retículo Endoplasmático , Proteínas de Membrana , Animais , Canais de Translocação SEC/genética , Canais de Translocação SEC/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/química , Retículo Endoplasmático/metabolismo , Mamíferos/metabolismo , Peptídeos/metabolismo , Transporte Proteico
7.
Int J Mol Sci ; 24(19)2023 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-37834237

RESUMO

The epithelial cell-adhesion molecule (EpCAM) is hyperglycosylated in carcinoma tissue and the oncogenic function of EpCAM primarily depends on the degree of glycosylation. Inhibiting EpCAM glycosylation is expected to have an inhibitory effect on cancer. We analyzed the relationship of BAP31 with 84 kinds of tumor-associated antigens and found that BAP31 is positively correlated with the protein level of EpCAM. Triple mutations of EpCAM N76/111/198A, which are no longer modified by glycosylation, were constructed to determine whether BAP31 has an effect on the glycosylation of EpCAM. Plasmids containing different C-termini of BAP31 were constructed to identify the regions of BAP31 that affects EpCAM glycosylation. Antibodies against BAP31 (165-205) were screened from a human phage single-domain antibody library and the effect of the antibody (VH-F12) on EpCAM glycosylation and anticancer was investigated. BAP31 increases protein levels of EpCAM by promoting its glycosylation. The amino acid region from 165 to 205 in BAP31 plays an important role in regulating the glycosylation of EpCAM. The antibody VH-F12 significantly inhibited glycosylation of EpCAM which, subsequently, reduced the adhesion of gastric cancer cells, inducing cytotoxic autophagy, inhibiting the AKT-PI3K-mTOR signaling pathway, and, finally, resulting in proliferation inhibition both in vitro and in vivo. Finally, we clarified that BAP31 plays a key role in promoting N-glycosylation of EpCAM by affecting the Sec61 translocation channels. Altogether, these data implied that BAP31 regulates the N-glycosylation of EpCAM and may represent a potential therapeutic target for cancer therapy.


Assuntos
Anticorpos , Antígenos de Neoplasias , Proteínas de Membrana , Humanos , Antígenos de Neoplasias/imunologia , Carcinoma , Linhagem Celular Tumoral , Molécula de Adesão da Célula Epitelial/genética , Molécula de Adesão da Célula Epitelial/metabolismo , Células Epiteliais/metabolismo , Glicosilação , Receptores de Antígenos de Linfócitos B/metabolismo , Canais de Translocação SEC/metabolismo , Proteínas de Membrana/imunologia
8.
Biophys J ; 122(22): 4382-4394, 2023 11 21.
Artigo em Inglês | MEDLINE | ID: mdl-37853695

RESUMO

The ß-barrel assembly machinery (BAM) complex is responsible for inserting outer membrane proteins (OMPs) into the Escherichia coli outer membrane. The SecYEG translocon inserts inner membrane proteins into the inner membrane and translocates both soluble proteins and nascent OMPs into the periplasm. Recent reports describe Sec possibly playing a direct role in OMP biogenesis through interactions with the soluble polypeptide transport-associated (POTRA) domains of BamA (the central OMP component of BAM). Here we probe the diffusion behavior of these protein complexes using photoactivatable super-resolution localization microscopy and single-particle tracking in live E. coli cells of BAM and SecYEG components BamA and SecE and compare them to other outer and inner membrane proteins. To accurately measure trajectories on the highly curved cell surface, three-dimensional tracking was performed using double-helix point-spread function microscopy. All proteins tested exhibit two diffusive modes characterized by "slow" and "fast" diffusion coefficients. We implement a diffusion coefficient analysis as a function of the measurement lag time to separate positional uncertainty from true mobility. The resulting true diffusion coefficients of the slow and fast modes showed a complete immobility of full-length BamA constructs in the time frame of the experiment, whereas the OMP OmpLA displayed a slow diffusion consistent with the high viscosity of the outer membrane. The periplasmic POTRA domains of BamA were found to anchor BAM to other cellular structures and render it immobile. However, deletion of individual distal POTRA domains resulted in increased mobility, suggesting that these domains are required for the full set of cellular interactions. SecE diffusion was much slower than that of the inner membrane protein PgpB and was more like OMPs and BamA. Strikingly, SecE diffused faster upon POTRA domain deletion. These results are consistent with the existence of a BAM-SecYEG trans-periplasmic assembly in live E. coli cells.


Assuntos
Proteínas de Escherichia coli , Escherichia coli , Escherichia coli/metabolismo , Canais de Translocação SEC/metabolismo , Proteínas de Escherichia coli/metabolismo , Membrana Celular/metabolismo , Proteínas da Membrana Bacteriana Externa/química , Dobramento de Proteína , Fosfatidato Fosfatase/metabolismo
9.
Aging (Albany NY) ; 15(20): 11508-11531, 2023 10 24.
Artigo em Inglês | MEDLINE | ID: mdl-37878007

RESUMO

BACKGROUND: Exosomes play a crucial role in tumor initiation and progression, yet the precise involvement of exosome-related genes (ERGs) in lung adenocarcinoma (LUAD) remains unclear. METHODS: We conducted a comprehensive investigation of ERGs within the tumor microenvironment (TME) of LUAD using single-cell RNA sequencing (scRNA-seq) analysis. Multiple scoring methods were employed to assess exosome activity (EA). Differences in cell communication were examined between high and low EA groups, utilizing the "CellChat" R package. Subsequently, we leveraged multiple bulk RNA-seq datasets to develop and validate exosome-associated signatures (EAS), enabling a multifaceted exploration of prognosis and immunotherapy outcomes between high- and low-risk groups. RESULTS: In the LUAD TME, epithelial cells demonstrated the highest EA, with even more elevated levels observed in advanced LUAD epithelial cells. The high-EA group exhibited enhanced intercellular interactions. EAS were established through the analysis of multiple bulk RNA-seq datasets. Patients in the high-risk group exhibited poorer overall survival (OS), reduced immune infiltration, and decreased expression of immune checkpoint genes. Finally, we experimentally validated the high expression of SEC61G in LUAD cell lines and demonstrated that knockdown of SEC61G reduced the proliferative capacity of LUAD cells using colony formation assays. CONCLUSION: The integration of single-cell and bulk RNA-seq analyses culminated in the development of the profound and significant EAS, which imparts invaluable insights for the clinical diagnosis and therapeutic management of LUAD patients.


Assuntos
Adenocarcinoma de Pulmão , Exossomos , Neoplasias Pulmonares , Humanos , Prognóstico , Exossomos/genética , Biomarcadores , Adenocarcinoma de Pulmão/genética , Adenocarcinoma de Pulmão/terapia , Imunoterapia , Análise de Célula Única , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/terapia , Microambiente Tumoral/genética , Canais de Translocação SEC
10.
Int J Mol Sci ; 24(18)2023 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-37762469

RESUMO

To elucidate the redundancy in the components for the targeting of membrane proteins to the endoplasmic reticulum (ER) and/or their insertion into the ER membrane under physiological conditions, we previously analyzed different human cells by label-free quantitative mass spectrometry. The HeLa and HEK293 cells had been depleted of a certain component by siRNA or CRISPR/Cas9 treatment or were deficient patient fibroblasts and compared to the respective control cells by differential protein abundance analysis. In addition to clients of the SRP and Sec61 complex, we identified membrane protein clients of components of the TRC/GET, SND, and PEX3 pathways for ER targeting, and Sec62, Sec63, TRAM1, and TRAP as putative auxiliary components of the Sec61 complex. Here, a comprehensive evaluation of these previously described differential protein abundance analyses, as well as similar analyses on the Sec61-co-operating EMC and the characteristics of the topogenic sequences of the various membrane protein clients, i.e., the client spectra of the components, are reported. As expected, the analysis characterized membrane protein precursors with cleavable amino-terminal signal peptides or amino-terminal transmembrane helices as predominant clients of SRP, as well as the Sec61 complex, while precursors with more central or even carboxy-terminal ones were found to dominate the client spectra of the SND and TRC/GET pathways for membrane targeting. For membrane protein insertion, the auxiliary Sec61 channel components indeed share the client spectra of the Sec61 complex to a large extent. However, we also detected some unexpected differences, particularly related to EMC, TRAP, and TRAM1. The possible mechanistic implications for membrane protein biogenesis at the human ER are discussed and can be expected to eventually advance our understanding of the mechanisms that are involved in the so-called Sec61-channelopathies, resulting from deficient ER protein import.


Assuntos
Retículo Endoplasmático , Proteínas de Membrana , Humanos , Células HEK293 , Canais de Translocação SEC , Espectrometria de Massas
12.
Toxins (Basel) ; 15(8)2023 08 02.
Artigo em Inglês | MEDLINE | ID: mdl-37624243

RESUMO

Mycolactone is an exotoxin produced by Mycobacterium ulcerans that causes the neglected tropical skin disease Buruli ulcer. This toxin inhibits the Sec61 translocon in the endoplasmic reticulum (ER), preventing the host cell from producing several secretory and transmembrane proteins, resulting in cytotoxic and immunomodulatory effects. Interestingly, only one of the two dominant isoforms of mycolactone is cytotoxic. Here, we investigate the origin of this specificity by performing extensive molecular dynamics (MD) simulations with enhanced free energy sampling to query the association trends of the two isoforms with both the Sec61 translocon, using two distinct cryo-electron microscopy (cryo-EM) models as references, and the ER membrane, which serves as a toxin reservoir prior to association. Our results suggest that mycolactone B (the cytotoxic isoform) has a stronger association with the ER membrane than mycolactone A due to more favorable interactions with membrane lipids and water molecules. This could increase the reservoir of toxin proximal to the Sec61 translocon. In one model of Sec61 inhibited by mycolactone, we find that isomer B interacts more closely with residues thought to play a key role in signal peptide recognition and, thus, are essential for subsequent protein translocation. In the other model, we find that isomer B interacts more closely with the lumenal and lateral gates of the translocon, the dynamics of which are essential for protein translocation. These interactions induce a more closed conformation, which has been suggested to block signal peptide insertion and subsequent protein translocation. Collectively, these findings suggest that isomer B's unique cytotoxicity is a consequence of both increased localization to the ER membrane and channel-locking association with the Sec61 translocon, facets that could be targeted in the development of Buruli Ulcer diagnostics and Sec61-targeted therapeutics.


Assuntos
Úlcera de Buruli , Humanos , Microscopia Crioeletrônica , Canais de Translocação SEC
13.
Med Sci (Basel) ; 11(3)2023 06 27.
Artigo em Inglês | MEDLINE | ID: mdl-37489460

RESUMO

Combining omics data from different layers using integrative methods provides a better understanding of the biology of a complex disease such as cancer. The discovery of biomarkers related to cancer development or prognosis helps to find more effective treatment options. This study integrates multi-omics data of different cancer types with a network-based approach to explore common gene modules among different tumors by running community detection methods on the integrated network. The common modules were evaluated by several biological metrics adapted to cancer. Then, a new prognostic scoring method was developed by weighting mRNA expression, methylation, and mutation status of genes. The survival analysis pointed out statistically significant results for GNG11, CBX2, CDKN3, ARHGEF10, CLN8, SEC61G and PTDSS1 genes. The literature search reveals that the identified biomarkers are associated with the same or different types of cancers. Our method does not only identify known cancer-specific biomarker genes, but also proposes new potential biomarkers. Thus, this study provides a rationale for identifying new gene targets and expanding treatment options across cancer types.


Assuntos
Multiômica , Neoplasias , Humanos , Prognóstico , Neoplasias/diagnóstico , Neoplasias/genética , Biomarcadores Tumorais/genética , Análise de Dados , Canais de Translocação SEC
14.
Mediators Inflamm ; 2023: 3648946, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37292257

RESUMO

Background: The clinical outcomes of low-grade glioma (LGG) are associated with T cell infiltration, but the specific contribution of heterogeneous T cell types remains unclear. Method: To study the different functions of T cells in LGG, we mapped the single-cell RNA sequencing results of 10 LGG samples to obtain T cell marker genes. In addition, bulk RNA data of 975 LGG samples were collected for model construction. Algorithms such as TIMER, CIBERSORT, QUANTISEQ, MCPCOUTER, XCELL, and EPIC were used to depict the tumor microenvironment landscape. Subsequently, three immunotherapy cohorts, PRJEB23709, GSE78820, and IMvigor210, were used to explore the efficacy of immunotherapy. Results: The Human Primary Cell Atlas was used as a reference dataset to identify each cell cluster; a total of 15 cell clusters were defined and cells in cluster 12 were defined as T cells. According to the distribution of T cell subsets (CD4+ T cell, CD8+ T cell, Naïve T cell, and Treg cell), we selected the differentially expressed genes. Among the CD4+ T cell subsets, we screened 3 T cell-related genes, and the rest were 28, 4, and 13, respectively. Subsequently, according to the T cell marker genes, we screened six genes for constructing the model, namely, RTN1, HERPUD1, MX1, SEC61G, HOPX, and CHI3L1. The ROC curve showed that the predictive ability of the prognostic model for 1, 3, and 5 years was 0.881, 0.817, and 0.749 in the TCGA cohort, respectively. In addition, we found that risk scores were positively correlated with immune infiltration and immune checkpoints. To this end, we obtained three immunotherapy cohorts to verify their predictive ability of immunotherapy effects and found that high-risk patients had better clinical effects of immunotherapy. Conclusion: This single-cell RNA sequencing combined with bulk RNA sequencing may elucidate the composition of the tumor microenvironment and pave the way for the treatment of low-grade gliomas.


Assuntos
Glioma , Análise da Expressão Gênica de Célula Única , Humanos , Prognóstico , Fatores de Transcrição , Linfócitos T CD4-Positivos , Complexo CD3 , Glioma/genética , Microambiente Tumoral/genética , Canais de Translocação SEC
15.
J Mol Biol ; 435(15): 168172, 2023 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-37290739

RESUMO

YidC is a member of the YidC/Oxa1/Alb3 protein family that is crucial for membrane protein biogenesis in the bacterial plasma membrane. While YidC facilitates the folding and complex assembly of membrane proteins along with the Sec translocon, it also functions as a Sec-independent membrane protein insertase in the YidC-only pathway. However, little is known about how membrane proteins are recognized and sorted by these pathways, especially in Gram-positive bacteria, for which only a small number of YidC substrates have been identified to date. In this study, we aimed to identify Bacillus subtilis membrane proteins whose membrane insertion depends on SpoIIIJ, the primary YidC homolog in B. subtilis. We took advantage of the translation arrest sequence of MifM, which can monitor YidC-dependent membrane insertion. Our systematic screening identified eight membrane proteins as candidate SpoIIIJ substrates. Results of our genetic study also suggest that the conserved arginine in the hydrophilic groove of SpoIIIJ is crucial for the membrane insertion of the substrates identified here. However, in contrast to MifM, a previously identified YidC substrate, the importance of the negatively charged residue on the substrates for membrane insertion varied depending on the substrate. These results suggest that B. subtilis YidC uses substrate-specific interactions to facilitate membrane insertion.


Assuntos
Bacillus subtilis , Proteínas de Bactérias , Proteínas de Membrana , Proteínas de Membrana Transportadoras , Bacillus subtilis/genética , Bacillus subtilis/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Membrana Celular/metabolismo , Proteínas de Escherichia coli/metabolismo , Proteínas de Membrana/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Canais de Translocação SEC/metabolismo , Especificidade por Substrato
16.
Nat Chem Biol ; 19(9): 1063-1071, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-37169959

RESUMO

The Sec61 complex forms a protein-conducting channel in the endoplasmic reticulum membrane that is required for secretion of soluble proteins and production of many membrane proteins. Several natural and synthetic small molecules specifically inhibit Sec61, generating cellular effects that are useful for therapeutic purposes, but their inhibitory mechanisms remain unclear. Here we present near-atomic-resolution structures of human Sec61 inhibited by a comprehensive panel of structurally distinct small molecules-cotransin, decatransin, apratoxin, ipomoeassin, mycolactone, cyclotriazadisulfonamide and eeyarestatin. All inhibitors bind to a common lipid-exposed pocket formed by the partially open lateral gate and plug domain of Sec61. Mutations conferring resistance to the inhibitors are clustered at this binding pocket. The structures indicate that Sec61 inhibitors stabilize the plug domain in a closed state, thereby preventing the protein-translocation pore from opening. Our study provides the atomic details of Sec61-inhibitor interactions and the structural framework for further pharmacological studies and drug design.


Assuntos
Retículo Endoplasmático , Proteínas de Membrana , Humanos , Retículo Endoplasmático/metabolismo , Proteínas de Membrana/metabolismo , Transporte Proteico/fisiologia , Canais de Translocação SEC/antagonistas & inibidores , Canais de Translocação SEC/química , Canais de Translocação SEC/metabolismo
17.
Nat Chem Biol ; 19(9): 1054-1062, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-37169961

RESUMO

Preventing the biogenesis of disease-relevant proteins is an attractive therapeutic strategy, but attempts to target essential protein biogenesis factors have been hampered by excessive toxicity. Here we describe KZR-8445, a cyclic depsipeptide that targets the Sec61 translocon and selectively disrupts secretory and membrane protein biogenesis in a signal peptide-dependent manner. KZR-8445 potently inhibits the secretion of pro-inflammatory cytokines in primary immune cells and is highly efficacious in a mouse model of rheumatoid arthritis. A cryogenic electron microscopy structure reveals that KZR-8445 occupies the fully opened Se61 lateral gate and blocks access to the lumenal plug domain. KZR-8445 binding stabilizes the lateral gate helices in a manner that traps select signal peptides in the Sec61 channel and prevents their movement into the lipid bilayer. Our results establish a framework for the structure-guided discovery of novel therapeutics that selectively modulate Sec61-mediated protein biogenesis.


Assuntos
Proteínas de Membrana , Sinais Direcionadores de Proteínas , Animais , Camundongos , Transporte Proteico , Proteínas de Membrana/metabolismo , Canais de Translocação SEC/química , Canais de Translocação SEC/genética , Canais de Translocação SEC/metabolismo , Biossíntese de Proteínas
18.
Nat Struct Mol Biol ; 30(6): 770-777, 2023 06.
Artigo em Inglês | MEDLINE | ID: mdl-37170030

RESUMO

The translocon-associated protein (TRAP) complex resides in the endoplasmic reticulum (ER) membrane and interacts with the Sec translocon and the ribosome to facilitate biogenesis of secretory and membrane proteins. TRAP plays a key role in the secretion of many hormones, including insulin. Here we reveal the molecular architecture of the mammalian TRAP complex and how it engages the translating ribosome associated with Sec61 translocon on the ER membrane. The TRAP complex is anchored to the ribosome via a long tether and its position is further stabilized by a finger-like loop. This positions a cradle-like lumenal domain of TRAP below the translocon for interactions with translocated nascent chains. Our structure-guided TRAP mutations in Caenorhabditis elegans lead to growth deficits associated with increased ER stress and defects in protein hormone secretion. These findings elucidate the molecular basis of the TRAP complex in the biogenesis and translocation of proteins at the ER.


Assuntos
Retículo Endoplasmático , Glicoproteínas de Membrana , Animais , Glicoproteínas de Membrana/metabolismo , Retículo Endoplasmático/metabolismo , Proteínas de Ligação ao Cálcio/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Canais de Translocação SEC/metabolismo , Transporte Proteico , Mamíferos/metabolismo
20.
Front Immunol ; 14: 1182307, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37251379

RESUMO

Background: Circadian rhythm disruption (CRD) represents a critical contributor to the pathogenesis of Alzheimer's disease (AD). Nonetheless, how CRD functions within the AD immune microenvironment remains to be illustrated. Methods: Circadian rhythm score (CRscore) was utilized to quantify the microenvironment status of circadian disruption in a single-cell RNA sequencing dataset derived from AD. Bulk transcriptome datasets from public repository were employed to validate the effectiveness and robustness of CRscore. A machine learning-based integrative model was applied for constructing a characteristic CRD signature, and RT-PCR analysis was employed to validate their expression levels. Results: We depicted the heterogeneity in B cells, CD4+ T cells, and CD8+ T cells based on the CRscore. Furthermore, we discovered that CRD might be strongly linked to the immunological and biological features of AD, as well as the pseudotime trajectories of major immune cell subtypes. Additionally, cell-cell interactions revealed that CRD was critical in the alternation of ligand-receptor pairs. Bulk sequencing analysis indicated that the CRscore was found to be a reliable predictive biomarker in AD patients. The characteristic CRD signature, which included 9 circadian-related genes (CRGs), was an independent risk factor that accurately predicted the onset of AD. Meanwhile, abnormal expression of several characteristic CRGs, including GLRX, MEF2C, PSMA5, NR4A1, SEC61G, RGS1, and CEBPB, was detected in neurons treated with Aß1-42 oligomer. Conclusion: Our study revealed CRD-based cell subtypes in the AD microenvironment at single-cell level and proposed a robust and promising CRD signature for AD diagnosis. A deeper knowledge of these mechanisms may provide novel possibilities for incorporating "circadian rhythm-based anti-dementia therapies" into the treatment protocols of individualized medicine.


Assuntos
Doença de Alzheimer , Humanos , Doença de Alzheimer/metabolismo , Linfócitos T CD8-Positivos/metabolismo , Ritmo Circadiano/genética , Transcriptoma , Análise de Sequência de RNA , Canais de Translocação SEC/metabolismo
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