Biology subjects

Ali, S.

Publications and source records attributed to Ali, S..

At least 73 records · Page 4Linked to original sources

bioRxiv2023

Glycan-specific IgM is critical for human immunity to Staphylococcus aureus

Staphylococcus aureus is a major human pathogen but the immune factors that protect against it remain elusive. In particular, high opsonic IgG titers achieved in preclinical S. aureus animal immunization studies have consistently failed to translate to protection in human clinical trials. Here, we investigated the antibody responses to a conserved surface glycan, Wall Teichoic Acid (WTA). IgM and IgG antibodies specific to WTA were universally present in plasma from healthy individuals. Functionally, WTA-specific IgM outperformed IgG in opsonophagocytic killing of S. aureus and conferred passive protection against S. aureus infection in vivo. In the clinical setting, WTA-specific IgM responses, but not IgG responses, were significantly lower in S. aureus bacteremia patients compared to healthy individuals, correlated with mortality risk and showed impaired bacterial opsonization. Our findings can guide risk stratification of hospitalized patients and inform future design of antibody-based therapies and vaccines against serious S. aureus infection.

microbiology↗

bioRxiv2023

Transcriptome based changes in expression of detoxification genes of Bemisia tabaci under destruxin A treatment

BackgroundBemisia tabaci is an important agricultural pest that has been causing significant economic losses to crops across the globe. Destruxins are secondary metabolites of entomopathogenic fungi which can be used as a potential biopesticide against B. tabaci. However, little is known about the molecular mechanism regulating the defense response of B. tabaci post destruxin application. ResultsIn this study, we explored the molecular responses of B. tabaci exposed to destruxin A (DA) using RNA-Seq and differentially expressed gene (DEG) analysis. A total of 1702, 616, and 555 DEGs were identified in B. tabaci after 4, 8, and 12 h of destruxin A treatment. In addition, 40 putative detoxification-related DEGs, including 29 cytochrome P450s (P450s), 5 glutathione S-transferases (GSTs), and 5 carboxylesterases (CarEs) were also identified. Quantitative real-time PCR analysis indicated that the expression profiles of 19 random DEGs were consistent with the RNA-Seq results. ConclusionThese findings serve as valuable information for a better understanding of the interaction and molecular mechanisms involved in the defense response of B. tabaci against DA.

molecular biology↗

bioRxiv2023

β-ionone regulates Arabidopsis thaliana transcriptome and increases its resistance against Botrytis cinerea

Carotenoids are isoprenoid pigments vital for photosynthesis. Moreover, they are the precursor of apocarotenoids that include the phytohormones abscisic acid (ABA) and strigolactones (SLs), and retrograde signaling molecules and growth regulators, such as {beta}-cyclocitral and zaxinone. The apocarotenoid {beta}-ionone ({beta}-I) was previously reported to exert antimicrobial effects. Here, we showed that the application of this scent to Arabidopsis plants at micromolar concentrations caused a global reprogramming of gene expression, affecting thousands of transcripts involved in stress tolerance, growth, hormone metabolism, pathogen defense and photosynthesis. These changes, along with modulating the levels of the phytohormones ABA, jasmonic acid and salicylic acid, led to enhanced Arabidopsis resistance to Botrytis cinerea (B.c.), one of the most aggressive and widespread pathogenic fungi affecting numerous plant hosts and causing severe losses of postharvest fruits. Pre-treatment of tobacco and tomato plants with {beta}-I followed by inoculation with B.c. confirms the conserved effect of {beta}-I and induced immune responses in leaves and fruits. Moreover, there was reduced susceptibility to B.c. in LYCOPENE {beta}-CYCLASE- expressing tomato fruits possessing elevated levels of the endogenous {beta}-I, indicating beneficial biological activities of this compound in planta. Our work unraveled {beta}-I as a further carotenoid-derived regulatory metabolite and opens up new possibilities to control B.c. infection by establishing this natural volatile as an environmentally friendly bio-fungicide.

plant biology↗

bioRxiv2023

High-resolution cryo-electron microscopy of the human CDK-activating kinase for structure-based drug design

Rational design of next-generation therapeutics can be facilitated by high-resolution structures of drug targets bound to small-molecule inhibitors. However, application of structure-based methods to macromolecules refractory to crystallisation has been hampered by the often-limiting resolution and throughput of cryogenic electron microscopy (cryo-EM). Here, we use high-resolution cryo-EM to determine structures of the CDK-activating kinase, a master regulator of cell growth and division, in its free and nucleotide-bound states and in complex with 14 inhibitors at up to 1.8 [A] resolution. Our structures provide detailed insight into inhibitor interactions and networks of water molecules in the active site of cyclin- dependent kinase 7. Our data support a previously proposed mechanism contributing to inhibitor selectivity, thereby providing the basis for rational design of next-generation therapeutics. Additionally, our results establish a methodological framework for the use of high-resolution cryo-EM in structure-based drug design.

molecular biology↗

bioRxiv2023

A reference assembly for the legume cover crop, hairy vetch (Vicia villosa)

Vicia villosa is an incompletely domesticated annual legume of the Fabaceae family native to Europe and Western Asia. V. villosa is widely used as a cover crop and as a forage due to its ability to withstand harsh winters. A reference-quality genome assembly (Vvill1.0) was prepared from low error rate long sequence reads to improve genetic-based trait selection of this species. The Vvill1.0 assembly includes seven scaffolds corresponding to the seven estimated linkage groups and comprising approximately 68% of the total genome size of 2.03 gigabase pairs (Gbp). This assembly is expected to be a useful resource for genetic improvement of this emerging cover crop species as well as to provide useful insights into plant genome evolution.

genomics↗

bioRxiv2023

PI3K block restores age-dependent neurovascular coupling defects associated with cerebral small vessel disease

Neurovascular coupling (NVC), a vital physiological process that rapidly and precisely directs localized blood flow to the most active regions of the brain, is accomplished in part by the vast network of cerebral capillaries acting as a sensory web capable of detecting increases in neuronal activity and orchestrating the dilation of upstream parenchymal arterioles. Here, we report a Col4a1 mutant mouse model of cerebral small vessel disease (cSVD) with age-dependent defects in capillary-to-arteriole dilation, functional hyperemia in the brain, and memory. The fundamental defect in aged mutant animals was the depletion of the minor membrane phospholipid phosphatidylinositol 4,5 bisphosphate (PIP2) in brain capillary endothelial cells, leading to the loss of inwardly rectifier K+ (Kir2.1) channel activity. Blocking phosphatidylinositol-3-kinase (PI3K), an enzyme that diminishes the bioavailability of PIP2 by converting it to phosphatidylinositol (3,4,5)-trisphosphate (PIP3), restored Kir2.1 channel activity, capillary-to-arteriole dilation, and functional hyperemia. In longitudinal studies, chronic PI3K inhibition also improved the memory function of aged Col4a1 mutant mice. Our data suggest that PI3K inhibition is a viable therapeutic strategy for treating defective NVC and cognitive impairment associated with cSVD. One-sentence summaryPI3K inhibition rescues neurovascular coupling defects in cerebral small vessel disease.

neuroscience↗

bioRxiv2023

Feeding Neurons Integrate Metabolic and Reproductive States in Mice

Trade-offs between metabolic and reproductive processes are important for survival, particularly in mammals that gestate their young. Puberty and reproduction, as energetically taxing life stages, are often gated by metabolic availability in animals with ovaries. How the nervous system coordinates these trade-offs is an active area of study. We identify somatostatin neurons of the tuberal nucleus (TNSST) as a node of the feeding circuit that alters feeding in a manner sensitive to metabolic and reproductive states in mice. Whereas chemogenetic activation of TNSST neurons increased food intake across sexes, selective ablation decreased food intake only in female mice during proestrus. Interestingly, this ablation effect was only apparent in animals with a low body mass. Fat transplantation and bioinformatics analysis of TNSST neuronal transcriptomes revealed white adipose as a key modulator of the effects of TNSST neurons on food intake. Together, these studies point to a mechanism whereby TNSST hypothalamic neurons modulate feeding by responding to varying levels of circulating estrogens differentially based on energy stores. This research provides insight into how neural circuits integrate reproductive and metabolic signals, and illustrates how gonadal steroid modulation of neuronal circuits can be context-dependent and gated by metabolic status.

neuroscience↗

bioRxiv2022

Characterization of a strain-specific CD-1 reference genome reveals potential inter- and intra-strain functional variability

BackgroundCD-1 is an outbred mouse stock that is frequently used in toxicology, pharmacology, and fundamental biomedical research. Although inbred strains are typically better suited for such studies due to minimal genetic variability, outbred stocks confer practical advantages over inbred strains, such as improved breeding performance and low cost. Knowledge of the full genetic variability of CD-1 would make it more useful in toxicology, pharmacology, and fundamental biomedical research. ResultsWe performed deep genomic DNA sequencing of CD-1 mice and used the data to identify genome-wide SNPs, indels, and germline transposable elements relative to the mm10 reference genome. We used multiple genome-wide sequencing data types and previously published CD-1 SNPs to validate our called variants. We used the called variants to construct a strain-specific CD-1 reference genome, which we show can improve mappability and reduce experimental biases from genome-wide sequencing data derived from CD-1 mice. Based on previously published ChIP-seq and ATAC-seq data, we find evidence that genetic variation between CD-1 individuals can lead to alterations in transcription factor binding. We also identified a number of variants in the coding region of genes which could have effects on splicing and translation of genes. ConclusionsWe have identified millions of previously unidentified CD-1 variants with the potential to confound studies involving CD-1. We used the identified variants to construct a CD-1-specific reference genome, which can improve accuracy and reduce bias when aligning genomics data derived from CD-1 individuals.

genomics↗

bioRxiv2022

BBIBP-CorV (Sinopharm) vaccination- induced immunity is affected by age, gender and prior COVID-19 and activates responses to spike and other antigens

Long-term solutions against SARS-CoV-2 infections require understanding of immune protection induced by different vaccine COVID-19 formulations. We investigated humoral and cellular immunity induced by Sinopharm (BBIBP-CorV) in a region of high SARS-CoV-2 seroprevalence. Levels of IgG antibodies to SARS-CoV-2 spike protein and its receptor-binding domain (RBD) were determined 24-weeks. Cellular immunity was investigated using a commercially available IFN-{gamma} release assay to SARS-CoV-2 spike (Ag1 and 2) and extended genome antigens (Ag3). Increasing IgG seropositivity to Spike protein and RBD was observed post-vaccination. Seropositivity was reduced in those over 50 years and raised in females and those with prior COVID-19. After 20 weeks post-vaccination, only one third of participants had positive T cell responses to SARS-CoV-2 antigens. Prior COVID-19 impacted IFN{gamma} responses, with reactivity enhanced in those infected earlier. The frequency of IFN{gamma} responses was highest to extended genome antigen set. Overall, BBIBP-CorV- induced antibody responses were impacted by age, gender and prior COVID-19. Cellular immunity was present in a limited number of individuals after 20 weeks but was enhanced by prior infection. This suggests the need for booster vaccinations in older individuals. BBIBP-CorV-induced cellular activation is broader than to spike, requiring further study to understand how to monitor vaccine effectiveness.

immunology↗

bioRxiv2022

Cortical Circuit Mechanisms of Multimodal Temporal Pattern Discrimination

Discriminating between temporal features in sensory stimuli is critical to complex behavior and decision making. However, how sensory cortical circuit mechanisms contribute to discrimination between subsecond temporal components in sensory events is unclear. To elucidate the mechanistic underpinnings of timing in primary visual cortex (V1), we recorded from V1 using 2-photon calcium imaging in awake-behaving mice performing a go/no-go discrimination timing task, which was composed of patterns of subsecond audio-visual stimuli. In both conditions, activity during the early stimulus period was temporally coordinated with the preferred stimulus. However, while network activity increased in the preferred condition, network activity was increasingly suppressed in the nonpreferred condition over the stimulus period. Our results demonstrate that discrimination between subsecond intervals that are contained in rhythmic patterns can be accomplished by local networks and suggest the contribution of neural resonance as a mechanism.

neuroscience↗

bioRxiv2022

Defective Ca2+- dependent activation of TRPM4 channels contributes to age-related cerebral small vessel disease in Col4a1 mutant mice

Humans and mice with mutations in COL4A1 and COL4A2 manifest hallmarks of cerebral small vessel disease (cSVD), but the pathogenic mechanisms are largely unknown. Mice with a missense mutation in Col4a1 at amino acid 1344 (Col4a1+/G1344D) exhibited age-dependent intracerebral hemorrhage (ICH) and brain lesions. Here we report that this pathology was associated with the loss of myogenic vasoconstriction, an intrinsic vascular response essential for the autoregulation of cerebral blood flow. Electrophysiological analyses showed that the loss of myogenic constriction resulted from blunted pressure-induced smooth muscle cell (SMC) membrane depolarization. Further, we found that dysregulation of membrane potential was associated with impaired Ca2+-dependent activation of large-conductance Ca2+-activated K+ (BK) and transient receptor potential melastatin 4 (TRPM4) cation channels linked to disruptions in sarcoplasmic reticulum (SR) Ca2+ signaling. Treating Col4a1+/G1344D mice with 4-phenylbutyrate, a compound that promotes the trafficking of misfolded proteins and alleviates SR stress, restored SR Ca2+ signaling, BK and TRPM4 channel activity, prevented loss of myogenic tone, and reduced ICH. We conclude that alterations in SR Ca2+ handling that impair membrane potential regulating ion channel activity result in dysregulation of SMC membrane potential and loss of myogenic tone contributing to age-related cSVD in Col4a1+/G1344D mice. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=85 SRC="FIGDIR/small/505186v3_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@11a8cb9org.highwire.dtl.DTLVardef@d00b8org.highwire.dtl.DTLVardef@1aa5b24org.highwire.dtl.DTLVardef@145a9c0_HPS_FORMAT_FIGEXP M_FIG C_FIG

pathology↗

bioRxiv2022

Transmembrane 163 (TMEM163) protein interacts with specific mammalian SLC30 zinc efflux transporter family members

Recently, we reported that TMEM163 is a zinc efflux transporter that likely belongs to the mammalian solute carrier 30 (Slc30/ZnT) subfamily of the cation diffusion facilitator (CDF) protein superfamily. We hypothesized that human TMEM163 forms functional heterodimers with ZNT proteins based on their subcellular localization overlapping with TMEM163 and previous reports that certain ZNT monomers interact with each other. In this study, we heterologously expressed individual constructs with a unique peptide tag containing TMEM163, ZNT1, ZNT2, ZNT3, and ZNT4 (negative control) or co-expressed TMEM163 with each ZNT in HEK-293 cells for co-immunoprecipitation (co-IP) experiments. We also co-expressed TMEM163 with two different peptide tags as a positive co-IP control. Western blot analyses revealed that TMEM163 dimerizes with itself but that it also heterodimerizes with ZNT1, ZNT2, ZNT3, and ZNT4 proteins. Native co-IP using mouse tissues confirmed the interactions while confocal microscopy revealed that TMEM163 and ZNT proteins partially co-localize in cells, suggesting that they exist as homodimers and heterodimers in their respective subcellular sites. Functional zinc flux assays using Fluozin-3 and Newport Green dyes show that cells expressing TMEM163 homodimers extruded zinc slightly less efficiently than cells expressing TMEM163/ZNT heterodimers. Cell surface biotinylation revealed a subtle change in the plasma membrane localization of TMEM163 upon co-expression with certain ZNT proteins, which possibly explains why zinc efflux is marginally different for TMEM163 homodimers than TMEM163/ZNT heterodimers. Overall, our results show that the interaction between TMEM163 and distinct ZNT proteins is functionally relevant and that their heterodimerization may serve to influence their zinc efflux activity within specific tissues or cell types. Research HighlightsO_LITMEM163 protein heterodimerizes with mammalian ZNT1, ZNT2, ZNT3 and ZNT4 zinc efflux transporters. C_LIO_LITMEM163 and ZNT proteins partially co-localize in their respective plasma membrane or subcellular compartments, suggesting distinct cellular roles as homodimers and heterodimers. C_LIO_LIThe zinc efflux activity of TMEM163 or ZNT protein homodimers did not markedly differ from their TMEM163/ZNT heterodimer counterparts. C_LIO_LIFunctional TMEM163/ZNT heterodimers give further credence to the role of TMEM163 as a bona fide member of the SLC30 protein family C_LI

cell biology↗

bioRxiv2022

The CDK7 inhibitor CT7001 (Samuraciclib) targets proliferation pathways to inhibit advanced prostate cancer

BackgroundCurrent strategies to inhibit the androgen receptor (AR) are circumvented in castration-resistant prostate cancer (CRPC). Cyclin-dependent kinase 7 (CDK7) promotes AR signalling, in addition to established roles in cell cycle and global transcription regulation, together, providing a rationale for its therapeutic targeting in CRPC. MethodsThe antitumour activity of CT7001, an orally bioavailable CDK7 inhibitor, was investigated across CRPC models in vitro and in xenograft models in vivo. Cell-based assays and transcriptomic analyses of treated xenografts were employed to investigate the mechanism driving activity of CT7001, alone and in combination with the antiandrogen enzalutamide. ResultsCT7001 selectively engages with CDK7 in prostate cancer cells, causing inhibition of proliferation and cell cycle arrest. Activation of p53, induction of apoptosis, and suppression of transcription mediated by full-length and constitutively active AR splice variants contribute to antitumour efficacy in vitro. Oral administration of CT7001 represses growth of CRPC xenografts and significantly augments growth inhibition achieved by enzalutamide. Transcriptome analyses of treated xenografts indicate cell cycle and AR inhibition as the mode of action of CT7001 in vivo. ConclusionsThis study supports CDK7 inhibition as a strategy to target deregulated cell proliferation and demonstrates CT7001 is a promising CRPC therapeutic, alone or in combination with AR-targeting compounds.

molecular biology↗

bioRxiv2022

ztf-16 is a novel heterochronic modulator that opposes adult cell fate in dauer and continuous life histories in Caenorhabditis elegans

Animal development is a complex yet robust process that can withstand lengthy and variable interruptions. In Caenorhabditis elegans, adverse conditions can trigger entry into dauer diapause, a stress-resistant, developmentally arrested stage that occurs midway through larval development. Favorable conditions promote recovery from dauer and the completion of development. During larval development, hypodermal seam cells are multipotent and divide at each stage. At adulthood, seam cells differentiate and express the adult-specific COL-19 collagen. The larval-to-adult transition is controlled by a network of genes called the heterochronic pathway, including the LIN-29 transcription factor that directly activates col-19 expression, and the let-7 microRNA that indirectly promotes lin-29 expression. Notably, most heterochronic genes that oppose adult cell fate are dispensable after dauer. We performed a genetic screen for heterochronic genes that act after dauer and identified ztf-16, encoding a zinc finger transcription factor in the hunchback/Ikaros-like family. We found that ztf-16 opposes precocious expression of the adult cell fate marker col-19p::gfp equally during both life histories, making ztf-16(-) the first precocious heterochronic mutant to be unaffected by dauer. Our data indicate that ztf-16 regulates col-19p::gfp via a novel, lin-29-independent mechanism. Endogenous ztf-16b::gfp expression is regulated by let-7 and ztf-16 acts genetically downstream of let-7, but lin-29 is not required for col-19p::gfp expression in ztf-16 mutant larvae or adults. Taken together, this work illuminates a novel aspect of the heterochronic pathway relevant to both dauer and non-dauer development.

genetics↗

bioRxiv2022

The Arabidopsis D27like1 is a novel Isomerase that Contributes to SL Biosynthesis and Negatively Impacts ABA Level

The enzyme DWARF27 (D27) catalyzes the reversible isomerization of all-trans- into 9-cis-{beta}-carotene, initiating strigolactone (SL) biosynthesis. Genomes of higher plants encode two D27-homologs, D27-like1 and -like2, with unknown functions. Here, we investigated the enzymatic activity and biological function of the Arabidopsis D27-like1. In vitro enzymatic assays and Expression in Synechocystis sp. PCC6803 revealed a yet not reported 13-cis/15-cis/9-cis- and a 9-cis/all-trans-{beta}-carotene isomerization. Although disruption of AtD27-like1 did not cause SL deficiency phenotypes, overexpression of AtD27-like1 in the Atd27 mutant restored the more-branching phenotype, indicating a contribution of AtD27-like1 to SL biosynthesis. Accordingly, generated Atd27 Atd27like1 double mutants showed more pronounced branching phenotype, compared to Atd27. The contribution of AtD27-like1 to SL biosynthesis is likely due to its formation of 9-cis-{beta}-carotene that was present at higher levels in AtD27-like1 overexpressing lines. In contrast, AtD27-like1 expression correlated negatively with the content of 9-cis-violaxanthin, a precursor of abscisic acid (ABA), in shoots. Consistently, ABA levels were higher in shoots and also in dry seeds of the Atd27like1 and Atd27 Atd27like1 mutants. Transgenic lines expressing {beta}-glucuronidase (GUS) driven by the AtD27LIKE1 promoter and transcript analysis performed with hormone-treated Arabidopsis seedlings unraveled that AtD27LIKE1 is expressed in different tissues and regulated ABA and auxin. Taken together, our work revealed a cis/cis-{beta}-carotene isomerase activity that affects the content of both cis-carotenoid derived plant hormones ABA and SLs.

plant biology↗

bioRxiv2022

A comparison between Mini-loop mediated isothermal amplification and polymerase spiral reaction for selective amplification of short template DNA

Isothermal amplification of circulating tumour-derived DNA (ctDNA) in the blood plasma could provide a rapid and cost effective alternative to PCR and NGS approaches for real-time cancer monitoring. Several variations of isothermal technologies exist, typically designed over unconstrained template length. Here, we compared the amplification efficiency of a compact loop mediated isothermal amplification reaction (termed AS-Mini-LAMP) with polymerase spiral reaction (PSR) suitable for analysis of ctDNA. Utilising 4-primers and targeting a 155 bp template encompassing the estrogen receptor (ESR1) c.1138G>C (p.E380Q) missense mutation. Using synthetic E380Q template DNA and Bst2.0 polymerase, results demonstrate that AS-Mini-LAMP was capable of selective mutant allele DNA amplification to a limit of 1,000 mutant copies, whereas no specific amplification was observed by PSR. The alternative use of Bst3.0 polymerase for either AS-Mini-LAMP or PSR revealed non-canonical events that underpin potentially misleading results when employing isothermal chemistries. In conclusion, AS-Mini-LAMP is more suited to mutation detection than PSR.

molecular biology↗

bioRxiv2022

Canonical Strigolactones Are Not the Tillering-Inhibitory Hormone but Rhizospheric Signals in Rice

The plant hormones strigolactones (SLs) regulate shoot branching and mediate the communication with symbiotic mycorrhizal fungi, but also with noxious root parasitic weeds, such as Striga spp. SLs derive from carlactone (CL) and are divided structurally into canonical and non-canonical SLs. However, the questions about particular biological functions of the two groups and the identification of the SL that inhibits shoot branching are still unanswered, hampering targeted modification of SL pattern towards improving plant architecture and resistance against Striga. Here, we reported that 4-deoxyorobanchol (4DO) and orobanchol, the two canonical SLs in rice, do not have major role in determining rice shoot architecture. CRISPR/Cas9 mediated Osmax1-900 mutants, lacking these two SLs, do not show the high tillering and dwarf phenotype typical for SL-deficient plants. However, the absence of 4DO and orobanchol in root exudates significantly decreased their capability in inducing Striga seed germination, while caused only a delay in root colonization by mycorrhizal fungi. To confirm the genetic evidence, we used the SL-biosynthesis inhibitor TIS108. Our results showed that TIS108 is a MAX1-specific inhibitor that lowers 4DO and orobanchol synthesis, conferring a resistance to Striga without a severe impact on rice architecture. Hence, our work uncovers the specific function of canonical SLs as rhizospheric signals and paves the way for establishing chemical and genetic based approaches for combating the root parasitic weeds, by targeted depletion of their release.

plant biology↗

bioRxiv2022

Dual role of an essential HtrA2/Omi protease in the human malaria parasite: maintenance of mitochondrial homeostasis and induction of apoptosis like cell death under cellular stress

HtrA family of serine protease is known to play role in mitochondrial homeostasis as well as in the programmed cell death. Mitochondrial homeostasis and metabolism are crucial for survival and propagation of malaria parasite within the host. Here we have functionally characterized a Plasmodium falciparum HtrA2 (PfHtrA2) protein, which harbours trypsin like protease activity that can be inhibited by its specific inhibitor, ucf-101. Transgenic parasite line was generated, using HA-glmS C-terminal tagging approach, for localization as well as for inducible knockdown of PfHtrA2. The PfHtrA2 was localized in the parasite mitochondrion during asexual life cycle. Genetic ablation of PfHtrA2 caused significant parasite growth inhibition, decreased replication of mtDNA, increased mitochondrial ROS production, caused mitochondrial fission/fragmentation, and hindered parasite development. However, ucf-101 treatment had no effect on the parasite growth, suggesting non-protease/chaperone role of PfHtrA2 in the parasite. Under cellular stress conditions, inhibition of PfHtrA2 by ucf-101 reduced activation of the caspase like protease as well as parasite cell death, suggesting involvement of protease activity of PfHtrA2 in apoptosis like cell death in the parasite. Under these cellular stress conditions, the PfHtrA2 gets processed but remains localized in the mitochondrion, suggesting that it acts within the mitochondrion by cleaving intra-mitochondrial substrate(s). This was further supported by trans-expression of PfHtrA2 protease domain in the parasite cytosol, which was unable to induce any cell death in the parasite. Overall, we show specific role of PfHtrA2 in maintaining mitochondrial homeostasis as well as in regulating the stress induced cell death.

cell biology↗