RESUMO
HIV-1 Vif recruits host cullin-RING-E3 ubiquitin ligase and CBFß to degrade the cellular APOBEC3 antiviral proteins through diverse interactions. Recent evidence has shown that Vif also degrades the regulatory subunits PPP2R5(A-E) of cellular protein phosphatase 2A to induce G2/M cell cycle arrest. As PPP2R5 proteins bear no functional or structural resemblance to A3s, it is unclear how Vif can recognize different sets of proteins. Here we report the cryogenic-electron microscopy structure of PPP2R5A in complex with HIV-1 Vif-CBFß-elongin B-elongin C at 3.58 Å resolution. The structure shows PPP2R5A binds across the Vif molecule, with biochemical and cellular studies confirming a distinct Vif-PPP2R5A interface that partially overlaps with those for A3s. Vif also blocks a canonical PPP2R5A substrate-binding site, indicating that it suppresses the phosphatase activities through both degradation-dependent and degradation-independent mechanisms. Our work identifies critical Vif motifs regulating the recognition of diverse A3 and PPP2R5A substrates, whereby disruption of these host-virus protein interactions could serve as potential targets for HIV-1 therapeutics.
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Phenoloxidase (PO) catalyzed melanization and other insect immune responses are mediated by serine proteases (SPs) and their noncatalytic homologs (SPHs). Many of these SP-like proteins have a regulatory clip domain and are called CLIPs. In most insects studied so far, PO precursors are activated by a PAP (i.e., PPO activating protease) and its cofactor of clip-domain SPHs. Although melanotic encapsulation is a well-known refractory mechanism of mosquitoes against malaria parasites, it is unclear if a cofactor is required for PPO activation. In Anopheles gambiae, CLIPA4 is 1:1 orthologous to Manduca sexta SPH2; CLIPs A5-7, A12-14, A26, A31, A32, E6, and E7 are 11:4 orthologous to M. sexta SPH1a, 1b, 4, and 101, SPH2 partners in the cofactors. Here we produced proCLIPs A4, A6, A7Δ, A12, and activated them with CLIPB9 or M. sexta PAP3. A. gambiae PPO2 and PPO7 were expressed in Escherichia coli for use as PAP substrates. CLIPB9 was mutated to CLIPB9Xa by including a Factor Xa cleavage site. CLIPA7Δ was a deletion mutant with a low complexity region removed. After PAP3 or CLIPB9Xa processing, CLIPA4 formed a high Mr complex with CLIPA6, A7Δ or A12, which assisted PPO2 and PPO7 activation. High levels of specific PO activity (55-85 U/µg for PO2 and 1131-1630 U/µg for PO7) were detected in vitro, indicating that cofactor-assisted PPO activation also occurs in this species. The cleavage sites and mechanisms for complex formation and cofactor function are like those reported in M. sexta and Drosophila melanogaster. In conclusion, these data suggest that the three (and perhaps more) SPHI-II pairs may form cofactors for CLIPB9-mediated activation of PPOs for melanotic encapsulation in A. gambiae.
Assuntos
Anopheles , Manduca , Animais , Serina Proteases/metabolismo , Anopheles/metabolismo , Drosophila melanogaster/metabolismo , Serina Endopeptidases , Catecol Oxidase/genética , Catecol Oxidase/metabolismo , Precursores Enzimáticos/genética , Precursores Enzimáticos/metabolismo , Monofenol Mono-Oxigenase , Manduca/metabolismo , Proteínas de Insetos/metabolismo , HemolinfaRESUMO
Increasing evidence has suggested that the HIV-1 capsid enters the nucleus in a largely assembled, intact form. However, not much is known about how the cone-shaped capsid interacts with the nucleoporins (NUPs) in the nuclear pore for crossing the nuclear pore complex. Here, we elucidate how NUP153 binds HIV-1 capsid by engaging the assembled capsid protein (CA) lattice. A bipartite motif containing both canonical and noncanonical interaction modules was identified at the C-terminal tail region of NUP153. The canonical cargo-targeting phenylalanine-glycine (FG) motif engaged the CA hexamer. By contrast, a previously unidentified triple-arginine (RRR) motif in NUP153 targeted HIV-1 capsid at the CA tri-hexamer interface in the capsid. HIV-1 infection studies indicated that both FG- and RRR-motifs were important for the nuclear import of HIV-1 cores. Moreover, the presence of NUP153 stabilized tubular CA assemblies in vitro. Our results provide molecular-level mechanistic evidence that NUP153 contributes to the entry of the intact capsid into the nucleus.
Assuntos
Infecções por HIV , Soropositividade para HIV , HIV-1 , Humanos , Proteínas do Capsídeo/metabolismo , Capsídeo/metabolismo , HIV-1/metabolismo , Transporte Ativo do Núcleo Celular , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Infecções por HIV/metabolismo , Poro Nuclear/metabolismoRESUMO
Lentiviral Vif molecules target the host antiviral APOBEC3 proteins for destruction in cellular ubiquitin-proteasome pathways. Different lentiviral Vifs have evolved to use the same canonical E3 ubiquitin ligase complexes, along with distinct noncanonical host cofactors for their activities. Unlike primate lentiviral Vif, which recruits CBFß as the noncanonical cofactor, nonprimate lentiviral Vif proteins have developed different cofactor recruitment mechanisms. Maedi-visna virus (MVV) sequesters CypA as the noncanonical cofactor for the Vif-mediated ubiquitination of ovine APOBEC3s. Here, we report the cryo-electron microscopy structure of MVV Vif in complex with CypA and E3 ligase components. The structure, along with our biochemical and functional analysis, reveals both conserved and unique structural elements of MVV Vif and its common and distinct interaction modes with various cognate cellular proteins, providing a further understanding of the evolutionary relationship between lentiviral Vifs and the molecular mechanisms by which they capture different host cofactors for immune evasion activities.
Assuntos
Vírus Visna-Maedi , Ovinos , Animais , Vírus Visna-Maedi/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Microscopia Crioeletrônica , Produtos do Gene vif/metabolismo , Evasão da Resposta ImuneRESUMO
Cadmium (Cd) is a widely distributed toxic heavy metal that enters the environment via anthropogenic mobilization and accumulates in plants and animals, causing metabolic abnormalities even mortality. Although the toxic effects and stress damage of cadmium have been investigated extensively over the past few decades, research on its ability to trigger ferroptosis, growth retardation, and behavioral abnormalities is insufficient. As a result, the effects of CdCl2 exposure on growth and development, activity and sleep, and ferroptosis in this study were examined in fruit fly (Drosophila melanogaster). When exposed to 0.5 mM CdCl2, the entire growth period from larvae to adults was prolonged, and the rates of pupation and eclosion were decreased. Additionally, CdCl2 exposure resulted in a decrease in body weight and individual size of fruit fly and high lethality rate. Moreover, CdCl2 exposure altered fruit fly behavior, including decreased activity and increased sleep duration, particularly in females. Ferrostatin-1 (Fer-1) is a potent selective ferroptosis inhibitor that effectively slows lipid hydroperoxide accumulation to rescue body size reduction and restore activity and sleep in CdCl2-exposed female flies. CdCl2 exposure could induce ferroptosis in fruit fly mechanistically, as evidenced by inhibition of Nrf2 signaling pathway, accumulation of lipid peroxidation, impairment of GPX4 antioxidant system, and upregulation of iron metabolism. Our findings suggest that Cd exposure triggers ferroptosis, which leads to growth retardation and behavioral disorders in fruit fly.
Assuntos
Cloreto de Cádmio , Ferroptose , Animais , Feminino , Cádmio/farmacologia , Cloretos , Drosophila , Drosophila melanogaster , Transtornos do CrescimentoRESUMO
The SARS-CoV-2 variant, Omicron (B.1.1.529), rapidly swept the world since its emergence. Compared with previous variants, Omicron has a high number of mutations, especially those in its spike glycoprotein that drastically dampen or abolish the efficacy of currently available vaccines and therapeutic antibodies. Several major sublineages of Omicron evolved, including BA.1, BA.1.1, BA.2, BA.2.12.1, BA.3, BA.4/5, and BA.2.75, which rapidly changing the global and regional landscape of the pandemic. Although vaccines are available, therapeutic antibodies remain critical for infected and especially hospitalized patients. To address this, we have designed and generated a panel of human/humanized therapeutic bispecific antibodies against Omicron and its sub-lineage variants, with activity spectrum against other lineages. Among these, the top clone CoV2-0213 has broadly potent activities against multiple SARS-CoV-2 ancestral and Omicron lineages, including BA.1, BA.1.1, BA.2, BA.2.12.1, BA.3, BA.4/5, and BA.2.75. We have solved the cryo-EM structure of the lead bi-specific antibody CoV-0213 and its major Fab arm MB.02. Three-dimensional structural analysis shows distinct epitope of antibody - spike receptor binding domain (RBD) interactions and reveals that both Fab fragments of CoV2-0213 can simultaneously target one single spike RBD or two adjacent ones in the same spike trimer, further corroborating its mechanism of action. CoV2-0213 represents a unique and potent broad-spectrum SARS-CoV-2 neutralizing bispecific antibody (nbsAb) against the currently circulating major Omicron variants (BA.1, BA.1.1, BA.2, BA.2.12.1, BA.2.75, BA.3, and BA.4/5). CoV2-0213 is primarily human and ready for translational testing as a countermeasure against the ever-evolving pathogen.
RESUMO
Peptidoglycan recognition proteins (PGRPs) detect invading bacteria to trigger or modulate immune responses in insects. While these roles are established in Drosophila, functional studies are not yet achieved at the PGRP family level in other insects. To attain this goal, we selected Manduca sexta PGRP12 and five of the nine secreted PGRPs for recombinant expression and biochemical characterization. We cloned PGRP2-5, 12 and 13 cDNAs, produced the proteins in full (PGRP2-5, 13) or in part (PGRP3s, 12e, 13N, 13C) in Sf9 cells, and tested their bindings of two muramyl pentapeptides by surface plasmon resonance, two soluble peptidoglycans by competitive ELISA, and four insoluble peptidoglycans and eight whole bacteria by a pull-down assay. Preferential binding of meso-diaminopimelic acid-peptidoglycans (DAP-PGs) was observed in all the proteins containing a peptidoglycan binding domain and, since PGRP6, 7 and 9 proteins were hardly detected in cell-free hemolymph, the reportoire of PGRPs (including PGRP1 published previously) in M. sexta hemolymph is likely adapted to mainly detect Gram-negative bacteria and certain Gram-positive bacteria with DAP-PGs located on their surface. After incubation with plasma from naïve larvae, PGRP2, 3f, 4, 5, 13f and 13N considerably stimulated prophenoloxidase activation in the absence of a bacterial elicitor. PGRP3s and 12e had much smaller effects. Inclusion of the full-length PGRPs and their regions in the plasma also led to proHP8 activation, supporting their connections to the Toll pathway, since HP8 is a SpÓtzle-1 processing enzyme in M. sexta. Together, these findings raised concerns on the common belief that the Toll-pathway is specific for Gram-positive bacteria in insects.
Assuntos
Manduca , Animais , Proteínas de Transporte , Ácido Diaminopimélico/metabolismo , Drosophila/metabolismo , Hemolinfa/metabolismo , Proteínas de Insetos/metabolismo , Radioisótopos de Nitrogênio/metabolismo , Peptidoglicano/químicaRESUMO
COVID-19 pathogen SARS-CoV-2 has infected hundreds of millions and caused over 5 million deaths to date. Although multiple vaccines are available, breakthrough infections occur especially by emerging variants. Effective therapeutic options such as monoclonal antibodies (mAbs) are still critical. Here, we report the development, cryo-EM structures, and functional analyses of mAbs that potently neutralize SARS-CoV-2 variants of concern. By high-throughput single cell sequencing of B cells from spike receptor binding domain (RBD) immunized animals, we identify two highly potent SARS-CoV-2 neutralizing mAb clones that have single-digit nanomolar affinity and low-picomolar avidity, and generate a bispecific antibody. Lead antibodies show strong inhibitory activity against historical SARS-CoV-2 and several emerging variants of concern. We solve several cryo-EM structures at ~3 Å resolution of these neutralizing antibodies in complex with prefusion spike trimer ectodomain, and reveal distinct epitopes, binding patterns, and conformations. The lead clones also show potent efficacy in vivo against authentic SARS-CoV-2 in both prophylactic and therapeutic settings. We also generate and characterize a humanized antibody to facilitate translation and drug development. The humanized clone also has strong potency against both the original virus and the B.1.617.2 Delta variant. These mAbs expand the repertoire of therapeutics against SARS-CoV-2 and emerging variants.
Assuntos
Anticorpos Monoclonais Humanizados/imunologia , Anticorpos Neutralizantes , Anticorpos Antivirais , COVID-19 , SARS-CoV-2 , Animais , Anticorpos Biespecíficos/imunologia , Anticorpos Neutralizantes/imunologia , Anticorpos Antivirais/imunologia , COVID-19/imunologia , Glicoproteína da Espícula de Coronavírus , Proteínas do Envelope ViralRESUMO
COVID-19 is a global crisis of unimagined dimensions. Currently, Remedesivir is only fully licensed FDA therapeutic. A major target of the vaccine effort is the SARS-CoV-2 spike-hACE2 interaction, and assessment of efficacy relies on time consuming neutralization assay. Here, we developed a cell fusion assay based upon spike-hACE2 interaction. The system was tested by transient co-transfection of 293T cells, which demonstrated good correlation with standard spike pseudotyping for inhibition by sera and biologics. Then established stable cell lines were very well behaved and gave even better correlation with pseudotyping results, after a short, overnight co-incubation. Results with the stable cell fusion assay also correlated well with those of a live virus assay. In summary we have established a rapid, reliable, and reproducible cell fusion assay that will serve to complement the other neutralization assays currently in use, is easy to implement in most laboratories, and may serve as the basis for high throughput screens to identify inhibitors of SARS-CoV-2 virus-cell binding and entry.
Assuntos
Enzima de Conversão de Angiotensina 2/metabolismo , Bioensaio/métodos , COVID-19/virologia , Receptores de Coronavírus/metabolismo , SARS-CoV-2/fisiologia , Glicoproteína da Espícula de Coronavírus/metabolismo , Enzima de Conversão de Angiotensina 2/genética , COVID-19/sangue , Fusão Celular , Células HEK293 , Humanos , Receptores de Coronavírus/genética , Glicoproteína da Espícula de Coronavírus/genética , Transfecção , Ligação ViralRESUMO
Macroalgae polysaccharides are phytochemicals that are beneficial to human health. In this study, response surface methodology was applied to optimize the extraction procedure of Pyropia yezoensis porphyran (PYP). The optimum extraction parameters were: 100 °C (temperature), 120 min (time), and 29.32 mL/g (liquid-solid ratio), and the maximum yield of PYP was 22.15 ± 0.55%. The physicochemical characteristics of PPYP, purified from PYP, were analyzed, along with its lipid-lowering effect, using HepG2 cells and Drosophila melanogaster larvae. PPYP was a ß-type sulfated hetero-rhamno-galactan-pyranose with a molecular weight of 151.6 kDa and a rhamnose-to-galactose molar ratio of 1:5.3. The results demonstrated that PPYP significantly reduced the triglyceride content in palmitic acid (PA)-induced HepG2 cells and high-sucrose-fed D. melanogaster larvae by regulating the expression of lipid metabolism-related genes, reducing lipogenesis and increasing fatty acid ß-oxidation. To summarize, PPYP can lower lipid levels in HepG2 cells and larval fat body (the functional homolog tissue of the human liver), suggesting that PPYP may be administered as a potential marine lipid-lowering drug.
Assuntos
Hipolipemiantes/isolamento & purificação , Metabolismo dos Lipídeos/efeitos dos fármacos , Lipídeos/antagonistas & inibidores , Rodófitas , Alga Marinha/isolamento & purificação , Sefarose/análogos & derivados , Animais , Drosophila melanogaster , Células Hep G2 , Humanos , Hipolipemiantes/farmacologia , Metabolismo dos Lipídeos/fisiologia , Extração Líquido-Líquido/métodos , Sefarose/isolamento & purificação , Sefarose/farmacologiaRESUMO
The mammalian apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3 (APOBEC3 or A3) family of cytidine deaminases restrict viral infections by mutating viral DNA and impeding reverse transcription. To overcome this antiviral activity, most lentiviruses express a viral accessory protein called the virion infectivity factor (Vif), which recruits A3 proteins to cullin-RING E3 ubiquitin ligases such as cullin-5 (Cul5) for ubiquitylation and subsequent proteasomal degradation. Although Vif proteins from primate lentiviruses such as HIV-1 utilize the transcription factor core-binding factor subunit beta as a noncanonical cofactor to stabilize the complex, the maedi-visna virus (MVV) Vif hijacks cyclophilin A (CypA) instead. Because core-binding factor subunit beta and CypA are both highly conserved among mammals, the requirement for two different cellular cofactors suggests that these two A3-targeting Vif proteins have different biochemical and structural properties. To investigate this topic, we used a combination of in vitro biochemical assays and in vivo A3 degradation assays to study motifs required for the MVV Vif to bind zinc ion, Cul5, and the cofactor CypA. Our results demonstrate that although some common motifs between the HIV-1 Vif and MVV Vif are involved in recruiting Cul5, different determinants in the MVV Vif are required for cofactor binding and stabilization of the E3 ligase complex, such as the zinc-binding motif and N- and C-terminal regions of the protein. Results from this study advance our understanding of the mechanism of MVV Vif recruitment of cellular factors and the evolution of lentiviral Vif proteins.
Assuntos
Vírus Visna-Maedi/metabolismo , Produtos do Gene vif do Vírus da Imunodeficiência Humana/metabolismo , Sequência de Aminoácidos , Proteínas Culina/metabolismo , Ciclofilina A/metabolismo , Ligação Proteica , Domínios Proteicos , Proteólise , Zinco/metabolismo , Produtos do Gene vif do Vírus da Imunodeficiência Humana/químicaRESUMO
COVID-19 pathogen SARS-CoV-2 has infected hundreds of millions and caused over 5 million deaths to date. Although multiple vaccines are available, breakthrough infections occur especially by emerging variants. Effective therapeutic options such as monoclonal antibodies (mAbs) are still critical. Here, we report the development, cryo-EM structures, and functional analyses of mAbs that potently neutralize SARS-CoV-2 variants of concern. By high-throughput single cell sequencing of B cells from spike receptor binding domain (RBD) immunized animals, we identified two highly potent SARS-CoV-2 neutralizing mAb clones that have single-digit nanomolar affinity and low-picomolar avidity, and generated a bispecific antibody. Lead antibodies showed strong inhibitory activity against historical SARS-CoV-2 and several emerging variants of concern. We solved several cryo-EM structures at â¼3 Å resolution of these neutralizing antibodies in complex with prefusion spike trimer ectodomain, and revealed distinct epitopes, binding patterns, and conformations. The lead clones also showed potent efficacy in vivo against authentic SARS-CoV-2 in both prophylactic and therapeutic settings. We also generated and characterized a humanized antibody to facilitate translation and drug development. The humanized clone also has strong potency against both the original virus and the B.1.617.2 Delta variant. These mAbs expand the repertoire of therapeutics against SARS-CoV-2 and emerging variants.
RESUMO
APOBEC3 (A3) proteins are a family of host antiviral restriction factors that potently inhibit various retroviral infections, including human immunodeficiency virus (HIV)-1. To overcome this restriction, HIV-1 virion infectivity factor (Vif) recruits the cellular cofactor CBFß to assist in targeting A3 proteins to a host E3 ligase complex for polyubiquitination and subsequent proteasomal degradation. Intervention of the Vif-A3 interactions could be a promising therapeutic strategy to facilitate A3-mediated suppression of HIV-1 in patients. In this structural snapshot, we review the structural features of the recently determined structure of human A3F in complex with HIV-1 Vif and its cofactor CBFß, discuss insights into the molecular principles of Vif-A3 interplay during the arms race between the virus and host, and highlight the therapeutic implications.
Assuntos
Desaminases APOBEC/ultraestrutura , Subunidade beta de Fator de Ligação ao Core/ultraestrutura , Infecções por HIV/genética , Interações Hospedeiro-Patógeno/genética , Produtos do Gene vif do Vírus da Imunodeficiência Humana/ultraestrutura , Desaminases APOBEC/genética , Subunidade beta de Fator de Ligação ao Core/genética , Infecções por HIV/virologia , HIV-1/genética , HIV-1/patogenicidade , Humanos , Ligação Proteica , Conformação Proteica , Ubiquitina-Proteína Ligases/genética , Ubiquitinação/genética , Vírion/genética , Vírion/patogenicidade , Produtos do Gene vif do Vírus da Imunodeficiência Humana/genéticaRESUMO
The causative virus of the COVID-19 pandemic, SARS-CoV-2, uses its nonstructural protein 1 (Nsp1) to suppress cellular, but not viral, protein synthesis through yet unknown mechanisms. We show here that among all viral proteins, Nsp1 has the largest impact on host viability in the cells of human lung origin. Differential expression analysis of mRNA-seq data revealed that Nsp1 broadly alters the cellular transcriptome. Our cryo-EM structure of the Nsp1-40S ribosome complex shows that Nsp1 inhibits translation by plugging the mRNA entry channel of the 40S. We also determined the structure of the 48S preinitiation complex formed by Nsp1, 40S, and the cricket paralysis virus internal ribosome entry site (IRES) RNA, which shows that it is nonfunctional because of the incorrect position of the mRNA 3' region. Our results elucidate the mechanism of host translation inhibition by SARS-CoV-2 and advance understanding of the impacts from a major pathogenicity factor of SARS-CoV-2.
Assuntos
COVID-19/metabolismo , Biossíntese de Proteínas , RNA Mensageiro/metabolismo , RNA Viral/metabolismo , SARS-CoV-2/metabolismo , SARS-CoV-2/patogenicidade , Proteínas não Estruturais Virais/metabolismo , Animais , COVID-19/genética , COVID-19/patologia , Chlorocebus aethiops , Microscopia Crioeletrônica , Humanos , RNA Mensageiro/genética , RNA Viral/genética , Subunidades Ribossômicas Menores de Eucariotos/genética , Subunidades Ribossômicas Menores de Eucariotos/metabolismo , Subunidades Ribossômicas Menores de Eucariotos/ultraestrutura , Subunidades Ribossômicas Menores de Eucariotos/virologia , SARS-CoV-2/genética , SARS-CoV-2/ultraestrutura , Células Vero , Proteínas não Estruturais Virais/genéticaRESUMO
HIV-1 virion infectivity factor (Vif) promotes degradation of the antiviral APOBEC3 (A3) proteins through the host ubiquitin-proteasome pathway to enable viral immune evasion. Disrupting Vif-A3 interactions to reinstate the A3-catalyzed suppression of human immunodeficiency virus type 1 (HIV-1) replication is a potential approach for antiviral therapeutics. However, the molecular mechanisms by which Vif recognizes A3 proteins remain elusive. Here we report a cryo-EM structure of the Vif-targeted C-terminal domain of human A3F in complex with HIV-1 Vif and the cellular cofactor core-binding factor beta (CBFß) at 3.9-Å resolution. The structure shows that Vif and CBFß form a platform to recruit A3F, revealing a direct A3F-recruiting role of CBFß beyond Vif stabilization, and captures multiple independent A3F-Vif interfaces. Together with our biochemical and cellular studies, our structural findings establish the molecular determinants that are critical for Vif-mediated neutralization of A3F and provide a comprehensive framework of how HIV-1 Vif hijacks the host protein degradation machinery to counteract viral restriction by A3F.
Assuntos
Citosina Desaminase/química , HIV-1/química , Produtos do Gene vif do Vírus da Imunodeficiência Humana/química , Subunidade beta de Fator de Ligação ao Core/química , Microscopia Crioeletrônica , Citosina Desaminase/antagonistas & inibidores , Citosina Desaminase/ultraestrutura , Humanos , Evasão da Resposta Imune , Modelos Moleculares , Conformação Proteica , Domínios Proteicos , Mapeamento de Interação de Proteínas , Proteólise , Relação Estrutura-Atividade , Produtos do Gene vif do Vírus da Imunodeficiência Humana/farmacologia , Produtos do Gene vif do Vírus da Imunodeficiência Humana/ultraestruturaRESUMO
The apolipoprotein B mRNA editing enzyme catalytic polypeptide-like 3 (APOBEC3 or A3) family of proteins functions in the innate immune system. The A3 proteins are interferon inducible and hypermutate deoxycytidine to deoxyuridine in foreign single-stranded DNA (ssDNA). However, this deaminase activity cannot discriminate between foreign and host ssDNA at the biochemical level, which presents a significant danger when A3 proteins gain access to the nucleus. Interestingly, this A3 capability can be harnessed when coupled with novel CRISPR-Cas9 proteins to create a targeted base editor. Specifically, A3A has been used in vitro to revert mutations associated with disease states. Recent structural studies have shown the importance of loop regions of A3A and A3G in ssDNA recognition and positioning for deamination. In this work, we further examined loop 1 of A3A to determine how it affects substrate selection, as well as the efficiency of deamination, in the hopes of advancing the potential of A3A in base editing technology. We found that mutating residue H29 enhanced deamination activity without changing substrate specificity. Also interestingly, we found that increasing the length of loop 1 decreases substrate specificity. Overall, these results lead to a better understanding of substrate recognition and deamination by A3A and the A3 family of proteins.
Assuntos
Citidina Desaminase/química , Citidina Desaminase/metabolismo , DNA de Cadeia Simples/química , DNA de Cadeia Simples/metabolismo , Proteínas/química , Proteínas/metabolismo , Sequência de Aminoácidos , Citidina Desaminase/genética , DNA de Cadeia Simples/genética , Desaminação/fisiologia , Humanos , Mutação/fisiologia , Ligação Proteica/fisiologia , Estrutura Secundária de Proteína , Proteínas/genéticaRESUMO
Peptidoglycan recognition proteins (PGRPs) recognize bacteria through their unique cell wall constituent, peptidoglycans (PGs). PGRPs are conserved from insects to mammals and all function in antibacterial defense. In the tobacco hornworm Manduca sexta, PGRP1 and microbe binding protein (MBP) interact with PGs and hemolymph protease-14 precursor (proHP14) to yield active HP14. HP14 triggers a serine protease network that produces active phenoloxidase (PO), Spätzle, and other cytokines to stimulate immune responses. PGRP1 binds preferentially to diaminopimelic acid (DAP)-PGs of Gram-negative bacteria and Gram-positive Bacillus and Clostridium species than Lys-PGs of other Gram-positive bacteria. In this study, we synthesized DAP- and Lys-muramyl pentapeptide (MPP) and monitored their associations with M. sexta PGRP1 by surface plasmon resonance. The Kd values (0.57⯵M for DAP-MPP and 45.6⯵M for Lys-MPP) agree with the differential recognition of DAP- and Lys-PGs. To reveal its structural basis, we produced the PGRP1 in insect cells and determined its structure at a resolution of 2.1â¯Å. The protein adopts a fold similar to those from other PGRPs with a classical L-shaped PG-binding groove. A unique loop lining the shallow groove suggests a different ligand-binding mechanism. In summary, this study provided new insights into the PG recognition by PGRPs, a critical first step that initiates the serine protease cascade.
Assuntos
Proteínas de Transporte/química , Proteínas de Insetos/química , Manduca/química , Animais , Manduca/imunologia , Simulação de Acoplamento Molecular , Peptidoglicano/química , Estrutura Secundária de Proteína , Receptores de Reconhecimento de Padrão/química , Ressonância de Plasmônio de SuperfícieRESUMO
Melanization is a universal defense mechanism of insects against microbial infection. During this response, phenoloxidase (PO) is activated from its precursor by prophenoloxidase activating protease (PAP), the terminal enzyme of a serine protease (SP) cascade. In the tobacco hornworm Manduca sexta, hemolymph protease-14 (HP14) is autoactivated from proHP14 to initiate the protease cascade after host proteins recognize invading pathogens. HP14, HP21, proHP1*, HP6, HP8, PAP1-3, and non-catalytic serine protease homologs (SPH1 and SPH2) constitute a portion of the extracellular SP-SPH system to mediate melanization and other immune responses. Here we report the expression, purification, and functional characterization of M. sexta HP2. The HP2 precursor is synthesized in hemocytes, fat body, integument, nerve and trachea. Its mRNA level is low in fat body of 5th instar larvae before wandering stage; abundance of the protein in hemolymph displays a similar pattern. HP2 exists as an active enzyme in plasma of the wandering larvae and pupae in the absence of an infection. HP14 cleaves proHP2 to yield active HP2. After incubating active HP2 with larval hemolymph, we detected higher levels of PO activity, i.e. an enhancement of proPO activation. HP2 cleaved proPAP2 (but not proPAP3 or proPAP1) to yield active PAP2, responsible for a major increase in IEARpNA hydrolysis. PAP2 activates proPOs in the presence of a cofactor of SPH1 and SPH2. In summary, we have identified a new member of the proPO activation system and reconstituted a pathway of HP14-HP2-PAP2-PO. Since high levels of HP2 mRNA were present in integument and active HP2 in plasma of wandering larvae, HP2 likely plays a role in cuticle melanization during pupation and protects host from microbial infection in a soil environment.
Assuntos
Endopeptidases/genética , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Insetos/genética , Manduca/enzimologia , Melaninas/genética , Monofenol Mono-Oxigenase/genética , Serina Endopeptidases/genética , Animais , Endopeptidases/imunologia , Corpo Adiposo/enzimologia , Corpo Adiposo/imunologia , Hemócitos/enzimologia , Hemócitos/imunologia , Hemolinfa/enzimologia , Hemolinfa/imunologia , Proteínas de Insetos/imunologia , Tegumento Comum , Larva/enzimologia , Larva/genética , Larva/crescimento & desenvolvimento , Larva/imunologia , Manduca/genética , Manduca/crescimento & desenvolvimento , Manduca/imunologia , Melaninas/imunologia , Monofenol Mono-Oxigenase/imunologia , Tecido Nervoso/enzimologia , Tecido Nervoso/imunologia , Isoformas de Proteínas/genética , Isoformas de Proteínas/imunologia , Pupa/enzimologia , Pupa/genética , Pupa/crescimento & desenvolvimento , Pupa/imunologia , Serina Endopeptidases/imunologia , Transdução de Sinais , Traqueia/enzimologia , Traqueia/imunologiaRESUMO
Manduca sexta, known as the tobacco hornworm or Carolina sphinx moth, is a lepidopteran insect that is used extensively as a model system for research in insect biochemistry, physiology, neurobiology, development, and immunity. One important benefit of this species as an experimental model is its extremely large size, reaching more than 10 g in the larval stage. M. sexta larvae feed on solanaceous plants and thus must tolerate a substantial challenge from plant allelochemicals, including nicotine. We report the sequence and annotation of the M. sexta genome, and a survey of gene expression in various tissues and developmental stages. The Msex_1.0 genome assembly resulted in a total genome size of 419.4 Mbp. Repetitive sequences accounted for 25.8% of the assembled genome. The official gene set is comprised of 15,451 protein-coding genes, of which 2498 were manually curated. Extensive RNA-seq data from many tissues and developmental stages were used to improve gene models and for insights into gene expression patterns. Genome wide synteny analysis indicated a high level of macrosynteny in the Lepidoptera. Annotation and analyses were carried out for gene families involved in a wide spectrum of biological processes, including apoptosis, vacuole sorting, growth and development, structures of exoskeleton, egg shells, and muscle, vision, chemosensation, ion channels, signal transduction, neuropeptide signaling, neurotransmitter synthesis and transport, nicotine tolerance, lipid metabolism, and immunity. This genome sequence, annotation, and analysis provide an important new resource from a well-studied model insect species and will facilitate further biochemical and mechanistic experimental studies of many biological systems in insects.