Biology subjects

Meir, A.

Publications and source records attributed to Meir, A..

14 recordsLinked to original sources

bioRxiv2026

Inhibition of VP2-mediated entry: a potential antiviral strategy to treat or prevent calicivirus disease

The Caliciviridae include many notable human and animal pathogens, including norovirus and sapovirus, which cause outbreaks of acute gastroenteritis. We previously demonstrated that, following receptor engagement, feline calicivirus (FCV) assembles a portal structure at a unique capsid three-fold axis. This comprises twelve copies of the minor capsid protein VP2 and is essential for genome delivery. We designed a short peptide based on our structure data that occludes the VP2 binding sites on the capsid surface, to prevent assembly of the VP2 portal and thereby halt the viral entry mechanism. Incubation with low micromolar concentrations of the peptide considerably reduced the infectivity of two laboratory strains and four clinical isolates of FCV associated with respiratory or virulent-systemic disease. Cryo-electron microscopy structures of FCV virions complexed with the peptide confirmed that the peptide occupies the VP2 binding site on the major capsid protein VP1, preventing portal assembly and subsequent genome delivery. Our data show that targeting VP2 is a viable antiviral approach to preventing calicivirus infection, with potential for the treatment or prevention of norovirus disease.

microbiology↗

bioRxiv2026

Sustained exposure to CAR-T cell secretome impairs human Hematopoietic Stem Cell function and is reversible by dual TNFα-IFNγ blockade

Prolonged cytopenias are a frequent complication of chimeric antigen receptor (CAR) T-cell therapies and are associated with increased infection risk and non-relapse mortality. Although inflammatory cytokines released during CAR-T cell activation have been implicated in immune effector cell-associated hematotoxicity (ICAHT), their direct effects on human hematopoietic stem and progenitor cells (HSPCs) function remains incompletely understood. Here, we established a reductionist model of CAR-T-associated hematotoxicity using conditioned media (CM) derived from activated CD19 CAR-T cells. Sustained exposure of human HSPCs to CAR-T-derived inflammatory secretome impaired HSPC expansion and reduced long-term repopulating capacity in xenotransplantation assays. In contrast, short-term exposure did not abrogate HSPC function, indicating that brief inflammatory signals can initiate durable reprogramming events, with functional consequences emerging during subsequent proliferative expansion. Mechanistically, CAR-T CM induced IFN{gamma}- and TNF-responsive transcriptional programs in HSPCs and promoted inflammatory myeloid skewing without evidence of apoptosis-dependent stem cell loss. Combined inhibition of IFN{gamma} and TNF restored HSPC expansion, normalized lineage output, reversed inflammatory transcriptional signatures, and rescued in vivo repopulating capacity without impairing CAR-T cytotoxic activity. These findings demonstrate that CAR-T-derived inflammatory signaling can directly impair human HSC function and identify dual TNF/ IFN{gamma} blockade as a potential strategy to mitigate CAR-T-associated hematotoxicity while preserving antitumor efficacy.

cell biology↗

bioRxiv2025

Substrate-enhanced filamentation of 3-methylcrotonyl-CoA carboxylase in Legionella pneumophila

3-Methylcrotonyl-CoA carboxylase (MCC) is a biotin-dependent carboxylase that metabolizes the amino acid leucine. MCC is present in bacteria, fungi, plants, and animals. In humans, its overexpression is linked to cancer, and its deficiency is linked to inborn errors of metabolism with severe consequences, so understanding its structure and function has far reaching implications. Here, we explore the MCC from Legionella pneumophila, a pathogenic bacterium with a biphasic life cycle. Our endogenous holoenzyme yielded the highest resolution cryo-EM structure of MCC to date, allowing for identification of protein components by the machine learning tool ModelAngelo, confirmed independently by mass spectrometry. We also observed, for the first time, enhanced filamentation of MCC upon substrate binding. We propose that this filamentation, previously observed in the eukaryotes, but not in bacteria, may be important for cellular processes such as differentiation of life cycle or cell division.

biochemistry↗

bioRxiv2025

CAR T-cells dysfunction in the central nervous system is mediated by BBB-induced activation-induced cell death

Chimeric Antigen Receptor (CAR) T-cells can eliminate leukemia and lymphoma within the central nervous system (CNS). Following a case with CD19+ relapse in the CNS in the presence of persisting Tisagenlecleucel, we generated several models to study CAR T-cells in the CNS. In both immunocompetent and humanized leukemia-bearing mice, CNS-residing CAR T-cells were shown to have inferior ex-vivo killing capacities compared to CAR T-cells harvested from the spleen or bone marrow of receptive mice. In a mechanistic work-up, we identified two contributing factors: First, CAR T-cells cultured in cerebrospinal fluid showed impaired cytotoxic and proliferative function compared to those in serum or other media. Second, using a unique in vitro human blood-brain barrier (BBB) model composed of endothelial cells and brain pericytes, we demonstrated that CAR T-cells that crossed the BBB exhibited antigen-independent activation and diminished cytolytic capacity. This led to increased activation-induced cell death of the BBB-migrating CAR T-cells and was confirmed to be independent of the CAR target and the costimulatory domain. Our findings add possible mechanisms of CAR T-cell resistance in the CNS, relevant for CNS hematologic and non-hematologic tumors.

cancer biology↗

bioRxiv2024

The T4bSS of Legionella features a two-step secretion pathway with an inner membrane intermediate for secretion of transmembrane effectors

To promote intracellular survival and infection, Legionella spp. translocate hundreds of effector proteins into eukaryotic host cells using a type IV b protein secretion system (T4bSS). T4bSS are well known to translocate soluble as well as transmembrane domain-containing effector proteins (TMD-effectors) but the mechanisms of secretion are still poorly understood. Herein we investigated the secretion of hydrophobic TMD-effectors, of which about 80 were previously reported to be encoded by L. pneumophila. A proteomic analysis of fractionated membranes revealed that TMD-effectors are targeted to and inserted into the bacterial inner membranes of L. pneumophila independent of the presence of a functional T4bSS. While the T4bSS chaperones IcmS and IcmW were critical for secretion of all tested TMD-effectors, they did not influence inner membrane targeting of these proteins. As for soluble effector proteins, translocation of TMD-effectors into host cells depended on a C-terminal secretion signal and this signal needed to be presented towards the cytoplasmic side of the inner membrane. A different secretion behavior of TMD- and soluble effectors and the need for small periplasmic loops within TMD-effectors provided strong evidence that TMD-effectors are secreted in a two-step secretion process: Initially, an inner membrane intermediate is formed, that is extracted towards the cytoplasmic side, possibly by the help of the type IV coupling protein complex and subsequently secreted into eukaryotic host cells by the T4bSS core complex. Overall, our study highlights the amazing versatility of T4bSS to secrete soluble and TMD-effectors from different subcellular locations of the bacterial cell.

microbiology↗

bioRxiv2022

A desert green alga that thrives at extreme high-light intensities using a unique photoin-hibition protection mechanism

While light is the driving force of photosynthesis, excessive light can be harmful. Photoinhibition, or light-induced photo-damage, is one of the key processes limiting photosynthesis. When the absorbed light exceeds the amount that can be dissipated by photosynthetic electron flow and other processes, damaging radicals are formed that mostly inactivate photosystem II (PSII). A well-defined mechanism that protects the photosynthetic apparatus from photoinhibition has been described in the model green alga Chlamydomonas reinhardtii and plants. Chlorella oha-dii is a green micro-alga, isolated from biological desert soil crusts, that thrives under extreme high light (HL) in which other organisms do not survive. Here, we show that this alga evolved unique protection mechanisms distinct from those of C. reinhardtii and plants. When grown under extreme HL, significant structural changes were noted in the C. ohadii thylakoids, including a drastic reduction in the antennae and the formation of stripped core PSII, lacking its outer and inner antennae. This is accompanied by a massive accumulation of protective carotenoids and proteins that scavenge harmful radicals. At the same time, several elements central to photoinhibition protection in C. reinhardtii, such as psbS, the stress-related light harvesting complex, PSII protein phosphorylation and state-transitions are entirely absent or were barely detected in C. ohadii. Taken together, a unique photoinhibition protection mechanism evolved in C. ohadii, enabling the species to thrive under extreme-light intensities where other photo-synthetic organisms fail to survive.

plant biology↗

bioRxiv2022

Melon pan-genome and multi-parental framework for high-resolution trait dissection

Linking between genotype and phenotype is a fundamental goal in biology and requires robust data for both layers. The prominent increase in plant genome sequencing and comparisons of multiple related individuals, exposed the abundance of structural genomic variation and suggest that a single reference genome cannot represent the complete sequence diversity of a crop species, leading to the expansion of the pan-genome concept. For high-resolution forward genetics, this unprecedented access to genomic variation should be paralleled by availability and phenotypic characterization of genetic diversity, and effective integration between these layers. Here, we describe a multi-parental framework for trait dissection in melon, leveraging a novel pan-genome constructed for this crop. Melon (Cucumis melo L.) is an important crop from the Cucurbitaceae family, which display extensive phenotypic variation available for breeding. A diverse core set of 25 founder lines (MelonCore25) was sequenced using a combination of short and long-read technologies and their genomes were assembled de novo. The construction of a melon pan-genome exposed substantial variation in genome size and structure, including detection of ~300,000 structural variants and ~9 million SNPs. A half-diallel derived set of 300 F2 populations representing all possible MelonCore25 parental combinations was constructed as framework for trait dissection through integration with the pan-genome. We demonstrate the potential of this unified framework for genetic analysis of various melon traits, including rind color and mottling pattern, fruit sugar content and resistance to fungal diseases. We anticipate that utilization of this integrated resource will enhance genetic dissection of important traits and accelerate melon breeding. Significance statementPan-genomes aim to address the abundance of genome structural variation within species for improved genomic analyses. New pan-genome, constructed from de novo genome assemblies of 25 diverse melon (Cucumis melo L.) accessions is integrated with a half-diallel derived set of 300 F2 populations representing all possible parental combinations. The potential of this unified multi-parental trait dissection framework for melon genetics and breeding is presented.

genetics↗

bioRxiv2021

Underground Heterosis for Melons Yield

Heterosis, the superiority of hybrids over their parents, is a major genetic force associated with plant fitness and crop yield enhancement. Understanding and predicting heterosis is crucial for evolutionary biology, as well as for plant and animal breeding. We investigated root-mediated yield heterosis in melons (Cucumis melo) by characterizing common variety grafted onto 190 hybrid rootstocks resulting from crossing 20 diverse inbreds in a diallel-mating scheme. Hybrid rootstocks improved yield by more than 40% compared to their parents and the best hybrid outperformed the reference commercial variety by 65% under both optimal and minimal irrigation treatments. To characterize the genetics of the underground heterosis we conducted whole-genome re-sequencing of the 20 founder lines, and showed that parental genetic distance was no predictor for the level of heterosis. Through inference of the 190 hybrids genotypes from their parental genomes, followed by genome-wide association analysis, we mapped multiple root-mediated yield QTLs. The yield enhancement of the four best-performing hybrid rootstocks was validated in multiple experiments with four different scion varieties. While root biology is receiving increased attention, most of the research is conducted using plants not amenable to grafting and, as a result, it is difficult to separate root and shoot effects. Here, we use the rich genetic and genomic resources of Cucumis melo, where grafting is a common practice, to dissect a unique phenomenon of root-mediated yield heterosis, by directly evaluating in the field the contribution of the roots to fruit yield. Our grafting approach is inverted to the common roots genetics research path that focuses mainly on variation in root system architecture rather than the ultimate root-mediated whole-plant performance, and is a step towards discovery of candidate genes involved in root function and yield enhancement. HighlightWe show that yield heterosis is significant in melon and controlled independently above and underground. Using common-scion grafting approach, we find that heritable rootstock-mediated variation in a diallel population is associated with substantial fruit yield heterosis.

plant biology↗

bioRxiv2021

The desert green algae Chlorella ohadii thrives at excessive high light intensities by exceptionally enhancing the mechanisms that protect photosynthesis from photoinhibition

Although light is the driving force of photosynthesis, excessive light can be harmful. One of the main processes that limits photosynthesis is photoinhibition, the process of light-induced photodamage. When the absorbed light exceeds the amount that is dissipated by photosynthetic electron flow and other processes, damaging radicals are formed that mostly inactivate photosystem II (PSII). Damaged PSII must be replaced by a newly repaired complex in order to preserve full photosynthetic activity. Chlorella ohadii is a green micro-alga, isolated from biological desert soil crusts, that thrives under extreme high light and is highly resistant to photoinhibition. Therefore, C. ohadii is an ideal model for studying the molecular mechanisms underlying protection against photoinhibition. Comparison of the thylakoids of C. ohadii cells that were grown under low light versus extreme high light intensities, found that the alga employs all three known photoinhibition protection mechanisms: i) massive reduction of the PSII antenna size; ii) accumulation of protective carotenoids; and iii) very rapid repair of photo-damaged reaction center proteins. This work elucidated the molecular mechanisms of photoinhibition resistance in one of the most light-tolerant photosynthetic organisms and shows how photoinhibition protection mechanisms evolved to marginal conditions, enabling photosynthesis-dependent life in severe habitats. One Sentence HighlightAnalysis of the photosynthetic properties of a desert algae that thrives at extreme high light intensities revealed protection from photoinhibition driven by the remarkable enhancement of three protection mechanisms.

plant biology↗

bioRxiv2020

Mouse model of SARS-CoV-2 reveals inflammatory role of type I interferon signaling

Severe Acute Respiratory Syndrome-Coronavirus 2 (SARS-Cov-2) has caused over 5,000,000 cases of Coronavirus disease (COVID-19) with significant fatality rate.1-3 Due to the urgency of this global pandemic, numerous therapeutic and vaccine trials have begun without customary safety and efficacy studies.4 Laboratory mice have been the stalwart of these types of studies; however, they do not support infection by SARS-CoV-2 due to the inability of its spike (S) protein to engage the mouse ortholog of its human entry receptor angiotensin-converting enzyme 2 (hACE2). While hACE2 transgenic mice support infection and pathogenesis,5 these mice are currently limited in availability and are restricted to a single genetic background. Here we report the development of a mouse model of SARS-CoV-2 based on adeno associated virus (AAV)-mediated expression of hACE2. These mice support viral replication and antibody production and exhibit pathologic findings found in COVID-19 patients as well as non-human primate models. Moreover, we show that type I interferons are unable to control SARS-CoV2 replication and drive pathologic responses. Thus, the hACE2-AAV mouse model enables rapid deployment for in-depth analysis following robust SARS-CoV-2 infection with authentic patient-derived virus in mice of diverse genetic backgrounds. This represents a much-needed platform for rapidly testing prophylactic and therapeutic strategies to combat COVID-19.

immunology↗

bioRxiv2019

Mutagenesis of two homologs ATP Binding cassette protein in tomato by CRISPR/Cas9 provide resistance against the plant parasite Phelipanche aegyptiaca

Plant parasitic weed Phelipanche aegyptiaca and Orobanche spp. are obligate plant parasites that cause heavy damage to agricultural crop plants. Germination of the parasite seeds require exposure to specific chemical known as strigolactone [SL]. The plant hormone SL is derived from plant carotenoids via cleavage by CCD7 and CCD8 enzymes and exuded by the host roots to the rhizosphere. Here, we provide evidence that CRISPR/Cas9 mediated targeted mutagenesis of two homologues ATP Binding cassette (ABC) protein in tomato (Solyc08g067610 and Solyc08g067620), significantly reduced the germination of the parasitic weed P.aegyptiaca. Constructs harboring specific single guide RNA were prepared and targeted against conserved region in the above tomato genes (Solyc08g067610 and Solyc08g067620). Selected T0-mutated tomato plants showed different type of deletions at both locuses. Furthermore, genotype analysis of T1 plants showed that the introduced mutations stably inherited to next generation with no identified off-targets. Mutated tomato lines, showed more branching, enhanced growth of axillary buds, reduced length of primary stems and significantly reduced development of the parasitic weed P. aegyptiaca as compared to wild type plants. Moreover, in ABCCas9 mutants the expression level of the genes (CCD8 and MAX1) related to SL biosynthesis were decreased, without alteration in the root extract orobanchol [SL] as compared to control plants. Development of genetic resistance based on genome editing of host key genes are novel approaches for enhancing host-parasite resistance. The current study offers insights into ABC protein homologs and mutagenesis of ABC protein that could be used in the development of efficient method to reduce parasitic weed germination.

plant biology↗

bioRxiv2019

Inhibiting the copper efflux system in microbes as a novel approach for developing antibiotics

Five out of six people receive at least one antibiotic prescription per year. However, the ever-expanding use of antibiotics in medicine, agriculture, and food production has accelerated the evolution of antibiotic-resistant bacteria, which, in turn, made the development of novel antibiotics based on new molecular targets a priority in medicinal chemistry. One way of possibly combatting resistant bacterial infections is by inhibiting the copper transporters in prokaryotic cells. Copper is a key element within all living cells, but it can be toxic in excess. Both eukaryotic and prokaryotic cells have developed distinct copper regulation systems to prevent its toxicity. Therefore, selectively targeting the prokaryotic copper regulation system might be an initial step in developing next-generation antibiotics. One such system is the Gram-negative bacterial CusCFBA efflux system. CusB is a key protein in this system and was previously reported to play an important role in opening the channel for efflux via significant structural changes upon copper binding while also controlling the assembly and disassembly process of the entire channel. In this study, we aimed to develop novel peptide copper channel blockers, designed by in silico calculations based on the structure of CusB. Using a combination of magnetic resonance spectroscopy and various biochemical methods, we found a lead peptide that promotes copper-induced cell toxicity. Targeting copper transport in bacteria has not yet been pursued as an antibiotic mechanism of action. Thus, our study lays the foundation for discovering novel antibiotics.\n\nAuthor SummaryHerein, we apply a novel approach for the development of a new generation of antibiotics based on copper toxicity. In cells, copper ions are double-edge swords. On the one hand, various enzymes depend on them as cofactors for catalysis, but on the other hand, they are highly toxic. Thus, cells have developed sophisticated regulation systems to very precisely control copper concentration. Prokaryotic organisms are more sensitive to copper than eukaryotic systems, and therefore they employ additional copper transporters that have no homology in the eukaryotic cells in general and specifically in the human cell. Here, we suggest to take advantage of this fact, by developing inhibitors against one of the bacterial copper transporter: CusCBA. The adaptor protein within this transporter, CusB, plays a critical role in the opening of the whole transporter. We designed a peptide that interfere with its proper function and assembly, and therefore inhibits the opening of the transporter upon copper stress. This study lays the foundation for designing better and novel antibiotics.

biochemistry↗

bioRxiv2019

Exploring the role of the various methionine residues in the Escherichia coli CusB adapter protein

The dissemination of resistant pathogenic microbes has become one of the most challenging problems that modern medicine has faced. Developing novel drugs based on new molecular targets that previously were not targeted, is therefore the highest priority in antibiotics research. One approach that has been recently suggested is to inhibit copper transporters in prokaryotic systems. Copper is required for many biological pathways, but sometimes it can harm the cell. Pathogenic systems have a highly sophisticated copper-regulation network; therefore, a better understanding of how this network operates at the molecular level should assist in developing the next generation of antibiotics. The CusB protein is part of the CusCBA periplasmic Cu(I) efflux system in Gram-negative bacteria, and it was recently reported to play a key role in the functioning of the whole CusCBA system, in which conformational changes as well as the assembly/disassembly process control the opening of the transporter. More knowledge of the underlying mechanism is needed to attain a full understanding of CusB functioning, which is associated with targeting specific and crucial residues in CusB. Here, we combine in-vitro structural measurements, which used EPR spectroscopy and UV-Vis measurements, with cell experiments to explore the role of the various methionine residues in CusB. We targeted two methionine residues (M227 and M241) that are essential for the proper function of CusB.

biophysics↗

bioRxiv2019

Multi-allelic APRR2 Gene is Associated with Fruit Pigment Accumulation in Melon and Watermelon

Color and pigment content are important aspects of fruit quality and consumer acceptance of cucurbit crops. Here, we describe the independent mapping and cloning of a common causative APRR2 gene regulating pigment accumulation in melon and watermelon. We initially show that the APRR2 transcription factor is causative for the qualitative difference between dark and light green rind in both crops. Further analyses establish the link between sequence or expression level variations in the CmAPRR2 gene and pigments content in the rind and flesh of mature melon fruits. GWAS of young fruit rind color in a panel composed of 177 diverse melon accessions did not result in any significant association, leading to an earlier assumption that multiple genes are involved in shaping the overall phenotypic variation at this trait. Through resequencing of 25 representative accessions and allelism tests between light rind accessions, we show that multiple independent SNPs in the CmAPRR2 gene are causative for the light rind phenotype. The multi-haplotypic nature of this gene explain the lack of detection power obtained through GBS-based GWAS and confirm the pivotal role of this gene in shaping fruit color variation in melon. This study demonstrates the power of combining bi- and multi-allelic designs with deep sequencing, to resolve lack of power due to high haplotypic diversity and low allele frequencies. Due to its central role and broad effect on pigment accumulation in fruits, the APRR2 gene is an attractive target for carotenoids bio-fortification of cucurbit crops.

plant biology↗