Biology subjects

Kesavardhana, S.

Publications and source records attributed to Kesavardhana, S..

5 recordsLinked to original sources

bioRxiv2026

DDX3X syndrome mutations lock DDX3X-RNA conformational states to drive persistent pathological condensation and neuronal death

DDX3X is a highly conserved RNA helicase associated with RNA metabolism, translation initiation, and deciding cell fate choices. Spontaneous mutations in DDX3X cause a rare genetic human disorder called DDX3X syndrome, showing a spectrum of neurodevelopmental and intellectual abnormalities. How missense mutations in DDX3X lead to aberrant cellular functions and pathological consequences is unclear. Here, we demonstrate that specific DDX3X syndrome missense mutations induce the formation of persistent, solid-like DDX3X stress granules by structurally altering the conformation of the DDX3X-RNA complex. Structural interrogation of DDX3X syndrome missense mutations revealed critical mutations that perturb the DDX3X-RNA complex, exhibit high clinical pathogenicity scores, and are associated with cancers. N and C-terminal mutations adjacent to the helicase domain of the DDX3X (F182V, I190S, T198P, L556S, and L559H) showed augmented stress granule (SG) assembly, and formation of persistent DDX3X-SGs in neuronal and non-neuronal cells. Intriguingly, these mutations altered the liquid-like properties of DDX3X-SGs, forming solid-like SGs. Mechanistically, these mutations drive the persistent DDX3X-SGs by either locking DDX3X in an open, RNA-bound conformation or by increasing the rigidity of the DDX3X-RNA complex (I190S; T198P), thereby conferring a loss of liquid-like properties. The persistent solid-like DDX3X-SGs preferentially promoted neuronal lytic cell death and did not affect translation. Also, the C-terminal L556S and L559H mutations, which form persistent granules, promoted the DDX3X-driven {beta}-amyloid aggregation. Our observations indicate that DDX3X syndrome mutations near the N- and C-termini promote the formation of solid-like DDX3X condensates, neuropathological aggregation, and neuronal cell death, which might underlie the disease pathogenesis in humans. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=133 SRC="FIGDIR/small/702492v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@164b436org.highwire.dtl.DTLVardef@73741aorg.highwire.dtl.DTLVardef@1cb6fcforg.highwire.dtl.DTLVardef@119b652_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2024

Decoding non-human mammalian adaptive signatures of 2.3.4.4b H5N1 to assess its human adaptive potential

The recent panzootic 2.3.4.4b clade H5N1 infected diverse non-human mammalian species globally, showed mammal-to-mammal transmission among them and caused sporadic human infections. However, whether 2.3.4.4b H5N1 circulating in non-human mammals can establish human infections and spread among humans is unclear. Gain-of-function research restrictions preclude assessing human adapting mutations of 2.3.4.4b H5N1. Here, we tracked the evolution of 2.3.4.4b H5N1 that infected non-human mammals and evaluated their ability to gain human adaptations. The non-human mammal 2.3.4.4b H5N1 partly acquired classical human adapting mutations, which are identical to the residues of H1N1pdm09 and seasonal human H3N2 infections while showing a few species-specific adaptations that might be potential barriers for successful human adaptations. Despite minimal changes in Hemagglutinin (HA), A160T and T199I mutations near the receptor binding site of HA in dairy cattle viruses indicate the rapid HA glycan surface evolution affecting virus entry and immune evasion. The quantitative assessment indicated that 2.3.4.4b H5N1 circulating in bears, cattle, dolphins, and foxes show higher human adaptive potential than other hosts. Also, H5N1 infections in mammals across time showed a unique set of adaptations in the 2.3.4.4b clade compared to previously circulating strains, especially the acquisition of Q591 adaptation in PB2 that enables human adaptation. Thus, 2.3.4.4b H5N1 acquires human adaptations due to natural selection pressure in non-human mammals. Overall, our study delineates human adaptation and infection risk of specific non-human mammalian circulating HPAI 2.3.4.4b H5N1 strains. O_FIG O_LINKSMALLFIG WIDTH=164 HEIGHT=200 SRC="FIGDIR/small/609722v1_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@2dde4borg.highwire.dtl.DTLVardef@15d4983org.highwire.dtl.DTLVardef@1857093org.highwire.dtl.DTLVardef@1a1eec2_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGRAPHICAL ABSTRACTC_FLOATNO C_FIG

microbiology↗

bioRxiv2024

Avian influenza virus neuraminidase stalk length and haemagglutinin glycosylation patterns reveal molecularly directed reassortment promoting the emergence of highly pathogenic clade 2.3.4.4b A (H5N1) viruses

The recently emerged panzootic clade 2.3.4.4b H5N1 influenza viruses show unprecedented extensive spread in wild birds and have been transmitted to several mammals, including humans. The virologic factors that have driven the success of the 2.3.4.4b H5N1 viruses, which has not been achieved by previous H5N1 clades, is unclear. We show that the 2.3.4.4b H5 haemagglutinin (HA) paired exclusively with full length (long stalk) N1 neuraminidase (NA) in birds and mammals, unlike previous clades of H5 viruses, which preferentially paired with N1 proteins with stalk deletions (short stalk). We found that the emergence of a 2.3.4.4b H5 HA with seven glycosylation sites was critical in driving its pairing with long stalk N1. The earlier H5 clades that paired with short stalk N1s showed a pattern of eight or more glycosylation sites. A prior shift in a glycosylation site from position 103 to 171 in the receptor binding domain of H5 HA and the subsequent S173A mutation that removed it triggered the emergence of 2.3.4.4b clade H5N1 viruses. Thus, the evolution of novel variations in the H5 HA and their preference for long stalk N1 pairing led to increased fitness and pathogenicity. These observations led us to establish and validate the hypothesis that the pairing of avian virus HA and NA subtypes is not stochastic but is rather molecularly programmed by HA glycosylation and NA stalk length, modulating fitness and emergence of novel avian influenza viruses. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=182 SRC="FIGDIR/small/595329v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@1659b26org.highwire.dtl.DTLVardef@1ace4b6org.highwire.dtl.DTLVardef@1db7c0corg.highwire.dtl.DTLVardef@ad3654_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2023

SARS-CoV-2 Nsp13 is a viral RHIM protein promoting cell death linked to Z-RNA sensing and ZBP1-RIPK3 signaling

RHIM is a protein motif in cell death proteins that assembles higher-order signaling complexes and triggers regulated cell death, which in itself limits virus spread and additionally triggers inflammation for mounting immune responses. A few DNA viruses employ viral RHIMs mimicking host RHIMs. However, these viral RHIMs counteract host cell death by interacting with host RHIM proteins and blocking complex formation to alleviate antiviral defenses. Whether RNA viruses operate such viral RHIMs remains unknown. RHIM-protein signaling promotes lung damage and cytokine storm in respiratory RNA virus infections, arguing the presence of viral RHIMs. Here, we report the novel viral RHIMs in Nsp13 and Nsp14 of SARS-CoV-2 and other bat RNA viruses, providing the basis for bats as the hosts for their evolution. Nsp13 promoted cell death in bat and human cells, however, viral RHIM of Nsp13 is more critical for human cell death than bat cells, suggesting species-specific regulation. The conformation of RNA-binding channel in Nsp13 is critical for cell death in bat and human cells. Nsp13 showed RHIM-dependent interactions with ZBP1 and RIPK3 and promoted the formation of large insoluble complexes of ZBP1 and RIPK3. Also, Nsp13 promoted ZBP1-RIPK3 signaling-mediated cell death dependent on intracellular RNA ligands. Intriguingly, the SARS-CoV-2 genome consists of bona fide Z-RNA-forming segments. These SARS-CoV-2 Z-RNA segments promoted Nsp13-dependent cell death, further revealing Nsp13s association with Z-RNA sensing and ZBP1-RIPK3 signaling. Our findings reveal the functional viral RHIMs of bat-originated RNA viruses regulating host cell death associated with Z-RNA sensing and ZBP1-RIPK3 signaling activation. These observations allow the understanding of mechanisms of cellular damage and cytokine storm in SARS-CoV-2 and other bat-originated RNA virus infections. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=144 SRC="FIGDIR/small/554434v2_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@f71c5aorg.highwire.dtl.DTLVardef@1666aa5org.highwire.dtl.DTLVardef@e37d82org.highwire.dtl.DTLVardef@145020f_HPS_FORMAT_FIGEXP M_FIG C_FIG One-sentence summaryBat-associated RNA viruses employ viral RHIMs and regulate host cell death.

immunology↗

bioRxiv2020

Za2 domain of ZBP1 is a molecular switch regulating Influenza-induced PANoptosis and perinatal lethality during development

Z-DNA-binding protein 1 (ZBP1) is an innate nucleic acid sensor which regulates host defense responses and development. ZBP1 activation triggers inflammation and pyroptosis, necroptosis, and apoptosis (PANoptosis) by activating RIPK3, caspase-8, and the NLRP3 inflammasome. ZBP1 is unique among innate sensors because of its N-terminal Z1 and Z2 domains, which bind to nucleic acids in the Z-conformation. However, the specific role of these Z domains in orchestrating ZBP1 activation and subsequent inflammation and cell death is not clear. Here we have generated Zbp1{Delta}Z2/{Delta}Z2 mice that lack the Z2 domain of ZBP1 and demonstrate that this domain is critical for influenza A virus (IAV)-induced PANoptosis and perinatal lethality in RIPK1-RHIM mutated (Ripk1RHIM/RHIM) mice. Deletion of the Z2 domain in ZBP1 abolished IAV-induced PANoptosis and NLRP3 inflammasome activation. Furthermore, deletion of the Z2 domain of ZBP1 was sufficient to rescue Ripk1RHIM/RHIM mice from the perinatal lethality which is caused by ZBP1-driven cell death and inflammation. Our findings identify the essential role of the Z2 domain of ZBP1 in physiological functions and establish a link between sensing of Z-RNAs via the Z2 domain and the promotion of influenza-induced PANoptosis and perinatal lethality.

immunology↗