Biology subjects

Johnson, R. M.

Publications and source records attributed to Johnson, R. M..

31 records · Page 2Linked to original sources

bioRxiv2022

Sexual transmission of Anopheles gambiae densovirus (AgDNV) leads to disseminated infection in mated females

BackgroundAnopheles gambiae densovirus (AgDNV) is an insect-specific, single-stranded DNA virus that infects An. gambiae, the major mosquito species responsible for transmitting malaria parasites throughout Sub-Saharan Africa. AgDNV is a benign virus that is very specific to its mosquito host and therefore has potential to serve as a vector control tool via paratransgenesis (genetic modification of mosquito symbionts) to limit transmission of human pathogens. Prior to being engineered into a control tool, the natural transmission dynamics of AgDNV between An. gambiae mosquitoes needs to be fully understood. Additionally, improved knowledge of AgDNV infection in male mosquitoes is needed. In this study, we examine the tissue tropism of AgDNV in the male reproductive tract and investigate both venereal and vertical transmission dynamics of the virus. MethodsAn. gambiae adult males were infected with AgDNV via micro-injection and reproductive tissues collected and assayed for AgDNV using qPCR. Next, uninfected females were introduced to AgDNV-infected or control males and, after several nights of mating, both the spermatheca and female carcass were assessed for venereally transmitted AgDNV. Finally, F1s from this cross were collected and assayed to quantify vertical transmission of the virus. ResultsAgDNV infected the reproductive tract of male mosquitoes, including the testes and male accessory glands (MAGs), without affecting mating rates. AgDNV-infected males venereally transmitted virus to females, and these venereally-infected females developed disseminated infection throughout the body. However, AgDNV was not vertically transmitted to F1s resulting from this cross. ConclusionsInfected male releases could be an effective strategy to introduce AgDNV-based paratransgenic tools into naive populations of An. gambiae females.

microbiology↗

bioRxiv2021

Phage-like particle vaccines are highly immunogenic and protect against pathogenic coronavirus infection and disease

The response by vaccine developers to the COVID-19 pandemic has been extraordinary with effective vaccines authorized for emergency use in the U.S. within one year of the appearance of the first COVID-19 cases. However, the emergence of SARS-CoV-2 variants and obstacles with the global rollout of new vaccines highlight the need for platforms that are amenable to rapid tuning and stable formulation to facilitate the logistics of vaccine delivery worldwide. We developed a "designer nanoparticle" platform using phage-like particles (PLPs) derived from bacteriophage lambda for multivalent display of antigens in rigorously defined ratios. Here, we engineered PLPs that display the receptor binding domain (RBD) protein from SARS-CoV-2 and MERS-CoV, alone (RBDSARS-PLPs, RBDMERS-PLPs) and in combination (hCoV-RBD PLPs). Functionalized particles possess physiochemical properties compatible with pharmaceutical standards and retain antigenicity. Following primary immunization, BALB/c mice immunized with RBDSARS- or RBDMERS-PLPs display serum RBD-specific IgG endpoint and live virus neutralization titers that, in the case of SARS-CoV-2, were comparable to those detected in convalescent plasma from infected patients. Further, these antibody levels remain elevated up to 6 months post-prime. In dose response studies, immunization with as little as one microgram of RBDSARS-PLPs elicited robust neutralizing antibody responses. Finally, animals immunized with RBDSARS-PLPs, RBDMERS-PLPs, and hCoV-RBD PLPs were protected against SARS-CoV-2 and/or MERS-CoV lung infection and disease. Collectively, these data suggest that the designer PLP system provides a platform for facile and rapid generation of single and multi-target vaccines.

immunology↗

bioRxiv2021

An adjuvanted SARS-CoV-2 RBD nanoparticle elicits neutralizing antibodies and fully protective immunity in aged mice

Development of affordable and effective vaccines that can also protect vulnerable populations such as the elderly from COVID-19-related morbidity and mortality is a public health priority. Here we took a systematic and iterative approach by testing several SARS-CoV-2 protein antigens and adjuvants to identify a combination that elicits neutralizing antibodies and protection in young and aged mice. In particular, SARS-CoV-2 receptorbinding domain (RBD) displayed as a protein nanoparticle (RBD-NP) was a highly effective antigen, and when formulated with an oil-in-water emulsion containing Carbohydrate fatty acid MonoSulphate derivative (CMS) induced the highest levels of cross-neutralizing antibodies compared to other oil-in-water emulsions or AS01B. Mechanistically, CMS induced antigen retention in the draining lymph node (dLN) and expression of cytokines, chemokines and type I interferon-stimulated genes at both injection site and dLN. Overall, CMS:RBD-NP is effective across multiple age groups and is an exemplar of a SARS-CoV-2 subunit vaccine tailored to the elderly.

immunology↗

bioRxiv2021

DegP initiates regulated processing of filamentous hemagglutinin in Bordetella bronchiseptica

Filamentous hemagglutinin (FhaB) is a critical virulence factor for both Bordetella pertussis, the causal agent of whooping cough, and the closely related species Bordetella bronchiseptica. FhaB is an adhesin, suppresses inflammatory cytokine production, and protects against phagocytic cell clearance during infection. Regulated degradation of the FhaB C-terminal prodomain is required to establish a persistent infection in mice. Two proteases, CtpA in the periplasm and SphB1 on the bacterial surface, are known to mediate FhaB processing, and we recently determined that CtpA functions before, and controls the FhaB cleavage site of, SphB1. However, the data indicate that another periplasmic protease must initiate degradation of the prodomain by removing a portion of the FhaB C terminus that inhibits CtpA-mediated degradation. Using a candidate approach, we identified DegP as the initiating protease. Deletion of degP or substitution of its predicted catalytic residue resulted in reduced creation of FHA', the main product of FhaB processing, and an accumulation of full-length FhaB in whole cell lysates. Also, FHA' was no longer released into culture supernatants in degP mutants. Alterations of the FhaB C terminus that relieve inhibition of CtpA abrogate the need for DegP, consistent with DegP functioning prior to CtpA in the processing pathway. DegP is not required for secretion of FhaB through FhaC or for adherence of the bacteria to host cells, indicating that DegP acts primarily as a protease and not a chaperone for FhaB in B. bronchiseptica. Our results highlight a role for HtrA family proteases in activation of virulence factors in pathogenic bacteria. ImportanceTwo-partner secretion (TPS) systems are broadly distributed among Gram-negative bacteria and play important roles in bacterial pathogenesis. FhaB-FhaC is the prototypical member of the TPS family and here we identified the protease that initiates a processing cascade that controls FhaB function. Our results are significant because they provide insight into the molecular mechanism underlying the ability of Bordetella species to prevent clearance by phagocytic cells, which is critical for bacterial persistence in the lower respiratory tract. Our findings also highlight an underappreciated role for HtrA family proteases in processing specific bacterial virulence factors.

microbiology↗

bioRxiv2021

Alum:CpG adjuvant enables SARS-CoV-2 RBD-induced protection in aged mice and synergistic activation of human elder type 1 immunity

Global deployment of vaccines that can provide protection across several age groups is still urgently needed to end the COVID-19 pandemic especially for low- and middle-income countries. While vaccines against SARS-CoV-2 based on mRNA and adenoviral-vector technologies have been rapidly developed, additional practical and scalable SARS-CoV-2 vaccines are needed to meet global demand. In this context, protein subunit vaccines formulated with appropriate adjuvants represent a promising approach to address this urgent need. Receptor-binding domain (RBD) is a key target of neutralizing antibodies (Abs) but is poorly immunogenic. We therefore compared pattern recognition receptor (PRR) agonists, including those activating STING, TLR3, TLR4 and TLR9, alone or formulated with aluminum hydroxide (AH), and benchmarked them to AS01B and AS03-like emulsion-based adjuvants for their potential to enhance RBD immunogenicity in young and aged mice. We found that the AH and CpG adjuvant formulation (AH:CpG) demonstrated the highest enhancement of anti-RBD neutralizing Ab titers in both age groups ([~]80-fold over AH), and protected aged mice from the SARS-CoV-2 challenge. Notably, AH:CpG-adjuvanted RBD vaccine elicited neutralizing Abs against both wild-type SARS-CoV-2 and B.1.351 variant at serum concentrations comparable to those induced by the authorized mRNA BNT162b2 vaccine. AH:CpG induced similar cytokine and chemokine gene enrichment patterns in the draining lymph nodes of both young adult and aged mice and synergistically enhanced cytokine and chemokine production in human young adult and elderly mononuclear cells. These data support further development of AH:CpG-adjuvanted RBD as an affordable vaccine that may be effective across multiple age groups. One Sentence SummaryAlum and CpG enhance SARS-CoV-2 RBD protective immunity, variant neutralization in aged mice and Th1-polarizing cytokine production by human elder leukocytes.

immunology↗

bioRxiv2021

A non-canonical role for glutamate decarboxylase 1 in cancer cell amino acid homeostasis, independent of the GABA shunt.

Glutamate decarboxylase 1 (GAD1) is best known for its role in producing the neurotransmitter {gamma}-amino butyric acid (GABA) as part of the "GABA shunt" metabolic pathway, an alternative mechanism of glutamine anaplerosis for TCA cycle metabolism (Yogeeswari et al., 2005). However, understanding of the metabolic function of GAD1 in non-neuronal tissues has remained limited. Here, we show that GAD1 supports cancer cell proliferation independent of the GABA shunt. Despite its elevated expression in lung cancer tissue, GAD1 is not engaged in the GABA shunt in proliferating non-small cell lung cancer (NSCLC) cells, but rather is required for regulating amino acid homeostasis. Silencing GAD1 promotes a broad deficiency in amino acid uptake, leading to reduced glutamine-dependent TCA cycle metabolism and defects in serum- and amino acid-stimulated mTORC1 activation. Mechanistically, GAD1 regulates amino acid uptake through ATF4-dependent amino acid transporter expression including SLC7A5 (LAT1), an amino acid transporter required for branched chain amino acid (BCAA) uptake. Overexpression of LAT1 rescues the proliferative and mTORC1 signalling defects of GAD1-deficient tumor cells. Our results, therefore, define a non-canonical role for GAD1, independent of its characterised role in GABA metabolism, whereby GAD1 regulates amino acid homeostasis to maintain tumor cell proliferation.

cancer biology↗

bioRxiv2021

Evolving cryo-EM structural approaches for GPCR drug discovery

G protein-coupled receptors (GPCRs) are the largest class of cell surface drug targets. Advances in biochemical approaches for the stabilisation of GPCR:transducer complexes together with improvements in the technology and application of cryo-EM has recently opened up new possibilities for structure-assisted drug design of GPCR agonists. Nonetheless, limitations in the commercial application of some of these approaches, including the use of nanobody 35 (Nb35) for stabilisation of GPCR:Gs complexes, and the high cost of 300kV imaging have restricted broad application of cryo-EM in drug discovery. Here, using the PF 06882961-bound GLP-1R as exemplar, we validated formation of stable complexes with a modified Gs protein in the absence of Nb35 that had equivalent resolution in the drug binding pocket to complexes solved in the presence of Nb35, while the G protein displayed increased conformational dynamics. In parallel, we assessed the performance of 200kV versus 300kV image acquisition using a Falcon 4 or K3 direct electron detector. We show that with 300kV Krios, both bottom mounted Falcon 4 and energy filtered (25eV slit) Bio-Quantum K3 produced similar resolution. Moreover, the 200kV Glacios with bottom mounted Falcon 4 yielded a 3.2 [A] map with clear density for bound drug and multiple structurally ordered waters. Our work paves the way for broader commercial application of cryo-EM for GPCR drug discovery.

biochemistry↗

bioRxiv2020

PHARMACOKINETICS OF TRANSBUCCAL SWAB-ADMINISTERED NALOXONE-HCL USING A NOVEL PLANT-BASED RESIN FORMULATION IN DOGS

A proof-of-concept transbuccal swab delivery of naloxone-HCL study using a mucoadhesive, plant-based film-forming resin formulation demonstrated comparable blood levels to benchmark intramuscular (IM) injection in highly predictive dog model. Results from this study allow the potential to translate rapid onset in humans with therapeutic blood levels being reached in 2-3 minutes comparable to that observed with commercially available parenteral injections and intranasal administrations. The simplicity, ease of delivery and rapid effectiveness has the potential to meet the public health emergency needs in the rescue of opioid overdosing.

pharmacology and toxicology↗

bioRxiv2020

Metabolic control of tumour extracellular matrix production in cancer-associated fibroblasts

TElevated production of collagen-rich extracellular matrix (ECM) is a hallmark of cancer associated fibroblasts (CAFs) and a central driver of cancer aggressiveness. How to target ECM production to oppose cancer is yet unclear, since targeting CAFs has been shown to restrain but also promote cancer progression. Metabolic rewiring is a hallmark of CAFs. Here we find that proline, which is a highly abundant amino acid in collagen proteins, is newly synthesised from glutamine to make tumour collagen in breast cancer xenografts, and that its production is elevated in breast cancer CAFs. PYCR1 is the rate-limiting enzyme for proline synthesis and is highly expressed in the tumour stroma of breast cancer patients and in CAFs. Reducing PYCR1 levels in CAFs is sufficient to reduce tumour collagen production, tumour growth and metastatic spread in vivo and cancer cell proliferation in vitro. PYCR1 and COL1A1 are overexpressed in patients with invasive ductal carcinoma with poor prognosis. Both collagen and glutamine-derived proline synthesis in CAFs are enhanced by increased pyruvate dehydrogenase-derived acetyl-CoA levels, via gene expression regulation through the epigenetic regulator histone acetyl transferase EP300. Altogether, our work unveils unprecedented roles of CAF metabolism to support pro-tumorigenic collagen production. PYCR1 is a recognised cancer cell vulnerability and potential target for therapy, hence, our work provides evidence that targeting PYCR1 in tumours may have the additional benefit of halting the production of pro-tumorigenic ECM.

cancer biology↗

bioRxiv2020

Cryo-EM structures of human TRPC5 reveal interaction of a xanthine-based TRPC1/4/5 inhibitor with a conserved lipid binding site.

TRPC1/4/5 channels are non-specific cation channels implicated in a wide variety of diseases, and TRPC1/4/5 inhibitors have recently entered the first clinical trials. However, fundamental and translational studies require a better understanding of TRPC1/4/5 channel regulation by endogenous and exogenous factors. Although several potent and selective TRPC1/4/5 modulators have been reported, the paucity of mechanistic insights into their modes-of-action remains a barrier to the development of new chemical probes and drug candidates. The xanthine class of modulators includes the most potent and selective TRPC1/4/5 inhibitors described to date, as well as TRPC5 activators. Our previous studies suggest that xanthines interact with a, so far, elusive pocket of TRPC1/4/5 channels that is essential to channel gating. Targeting this pocket may be a promising strategy for TRPC1/4/5 drug discovery. Here we report the first structure of a small molecule-bound TRPC1/4/5 channel - human TRPC5 in complex with the xanthine Pico145 - to 3.0 [A]. We found that Pico145 binds to a conserved lipid binding site of TRPC5, where it displaces a bound phospholipid. Our findings explain the mode-of-action of xanthine-based TRPC1/4/5 modulators, and suggest a structural basis for TRPC1/4/5 modulation by endogenous factors such as (phospho)lipids and Zn2+ ions. These studies lay the foundations for the structure-based design of new generations of TRPC1/4/5 modulators.

molecular biology↗

bioRxiv2019

Honey bee pollen foraging ecology across an urbanization gradient

Understanding animal foraging ecology requires large samples sizes spanning broad environmental and temporal gradients. For pollinators, this has been hampered by the laborious nature of morphologically identifying pollen. Metagenetic pollen analysis is a solution to this issue, but the field has struggled with poor quantitative performance. Building upon prior laboratory and bioinformatic methods, we applied quantitative multi-locus metabarcoding to characterize the foraging ecology of honey bee colonies situated along an urban-agricultural gradient in central Ohio, USA. In cross-validating a subset of our metabarcoding results using microscopic palynology, we find strong concordance between the molecular and microscopic methods. Our results show that, relative to the agricultural environment, urban and suburban environments were associated with higher taxonomic diversity and temporal turnover of honey bee pollen forage. This is likely reflective of the fine-grain heterogeneity and high beta diversity of urban floral landscapes at the scale of honey bee foraging. Our work also demonstrates the power of honey bees as environmental samplers of floral community composition at large spatial scales, aiding in the distinction of taxa characteristically associated with urban or agricultural land use from those distributed ubiquitously across our landscape gradient.

ecology↗

bioRxiv2019

Structure-based identification and characterisation of novel inhibitors of KNa1.1 potassium channels, a stratified target for KCNT1-related epilepsy.

Several types of drug-resistant epileptic encephalopathies of infancy have been associated with mutations in the KCNT1 gene, which encodes the sodium-activated potassium channel subunit KNa1.1. These mutations are commonly gain-of-function, increasing channel activity, therefore inhibition by drugs is proposed as a stratified approach to treat disorders. To date, quinidine therapy has been trialled with several patients, but mostly with unsuccessful outcomes, which has been linked to its low potency and lack of specificity. Here we describe the use of a cryo-electron microscopy-derived KNa1.1 structure and mutational analysis to identify the quinidine biding site and identified novel inhibitors that target this site using computational methods. We describe six compounds that inhibit KNa1.1 channels with low- and sub-micromolar potencies, likely through binding in the intracellular pore vestibule. In preliminary hERG inhibition and cytotoxicity assays, two compounds showed little effect. These compounds may provide starting points for the development of novel pharmacophores for KNa1.1 inhibition, with the view to treating KCNT1-associated epilepsy and, with their potencies higher than quinidine, could become key tool compounds to further study this channel. Furthermore, this study illustrates the potential for utilising cryo-electron microscopy in ion channel drug discovery.

pharmacology and toxicology↗

bioRxiv2018

Taxonomic identification from metagenomic and metabarcoding data using any genetic marker

Correct taxonomic identification of DNA sequences is central to studies of biodiversity using both shotgun metagenomic and metabarcoding approaches. However, there is no genetic marker that gives sufficient performance across all the biological kingdoms, hampering studies of taxonomic diversity in many groups of organisms. We here present a major update to Metaxa2 (http://microbiology.se/software/metaxa2/) that enables the use of any genetic marker for taxonomic classification of metagenome and amplicon sequence data.

bioinformatics↗