Biology subjects

Ismail, H.

Publications and source records attributed to Ismail, H..

7 recordsLinked to original sources

bioRxiv2026

Integrative genetic and structural analyses reveal nitric oxide-driven regulation of ERFVII stability in Arabidopsis under low O2

Nitric oxide (NO) is a key signaling molecule that regulates diverse physiological responses, including adaptation to hypoxia in plants. Although stabilization of group-VII ETHYLENE RESPONSE FACTOR (ERFVII) transcription factors under low O2 is known to be facilitated by the N-dragon pathway, whether NO directly mediates N-terminal cysteine (Cys) oxidation to regulate ERFVII stability remains unresolved. Here, we combined genetic, computational, and structural approaches to investigate NOs role in proteasomal degradation of ERFVII during flooding stress. Arabidopsis mutants with elevated S-Nitrosoglutathione (GSNO) levels compromised ERFVII activation during dark submergence but increased expression of genes encoding N-degron pathway enzymes. Although direct detection of in vivo NO-mediated S-nitrosylated proteins remains technically challenging, the GPS-SNO 1.0 tool predicted the conserved N-terminal second Cys residue as a high-confidence S-nitrosylation site. Structural modeling using the Schrodinger Suite 2024-4 further revealed that conversion of the Cys thiol (Cys-SH) to S-nitrosothiol (Cys-SNO) induced notable conformational changes in ERFVII TFs. Molecular docking further demonstrated that Cys-SNO-modified ERFVII peptides exhibited stronger binding affinities and altered interaction networks with N-degron pathway enzymes, supporting a role for NO-mediated structural remodeling in ERFVII degradation. Elevated GSNO also disrupted energy balance efficiency for overcoming O2 deficiency, altered the expression of sugar starvation-responsive genes, and impaired ATP binding capacity of Cys-SNO ERFVII proteins, as evidenced by docking and molecular dynamics simulations. Collectively, these results support a model in which NO-mediated modification of the conserved N-terminal Cys promotes ERFVII degradation, thereby linking NO signaling to hypoxia-responsive transcriptional regulation and metabolic adaptation during flooding stress.

plant biology↗

bioRxiv2026

Widely circulating pyrethroid resistance mechanisms reduce the efficacy of transfluthrin and pose a risk for mosquito-borne disease control with spatial emanators

Spatial emanators (SE) are a promising complement to existing tools for preventing mosquito transmitted diseases. In 2025, the WHO updated the WHO Guidelines for Malaria to include a conditional recommendation for the indoor use of prequalified SE products in malaria control. Both prequalified, and many other SE products contain the volatile pyrethroid transfluthrin, which shares the same target site as other (contact/solid phase) pyrethroids. Therefore, an assessment of cross resistance is critical to predict effectiveness against mosquitoes with existing pyrethroid resistance. Our results show that resistance to solid phase pyrethroids is correlated with resistance to transfluthrin in Anopheles and Aedes species. Moreover, commonly-selected resistance mechanisms including target site mutations and over-expression of P450 detoxification enzymes can confer resistance to transfluthrin. Furthermore, we show that resistant mosquitoes are less impacted by transfluthrin in terms of flight activation (irritancy) and reduced blood feeding inhibition, with the response correlating with resistance strength. Transfluthrin did not elicit an electroantennography response in Anopheles gambiae and surgically ablating mosquitoes antennae did not result in differences in flight activation upon transfluthrin exposure, suggesting the antennae are not required for transfluthrin to elicit behavioral responses. These results provide new insight regarding the mode of action of transfluthrin and the risk of resistance reducing transfluthrins efficacy in vector control interventions.

pharmacology and toxicology↗

bioRxiv2024

Geranylgeranylated-SCFFBXO10 Regulates Selective Outer Mitochondrial Membrane Proteostasis and Function

E3-ubiquitin ligases (E3s) are main components of the ubiquitin-proteasome system (UPS), as they determine substrate specificity in response to internal and external cues to regulate protein homeostasis. However, the regulation of membrane protein ubiquitination by E3s within distinct cell membrane compartments or organelles is not well understood. We show that FBXO10, the interchangeable component of the SKP1/CUL1/F-box ubiquitin ligase complex (SCF-E3), undergoes lipid-modification with geranylgeranyl isoprenoid at Cysteine953 (C953), facilitating its dynamic trafficking to the outer mitochondrial membrane (OMM). FBXO10 polypeptide does not contain a canonical mitochondrial targeting sequence (MTS); instead, its geranylgeranylation at C953 and the interaction with two cytosolic factors, PDE6{delta} (a prenyl group-binding protein), and HSP90 (a mitochondrial chaperone) orchestrate specific OMM targeting of prenyl-FBXO10 across diverse membrane compartments. The geranylgeranylation-deficient FBXO10(C953S) mutant redistributes away from the OMM, leading to impaired mitochondrial ATP production, decreased mitochondrial membrane potential, and increased mitochondrial fragmentation. Phosphoglycerate mutase 5 (PGAM5) was identified as a potential substrate of FBXO10 at the OMM using comparative quantitative mass spectrometry analyses of enriched mitochondria (LFQ-MS/MS), leveraging the redistribution of FBXO10(C953S). FBXO10, but not FBXO10(C953S), promoted polyubiquitylation and degradation of PGAM5. Examination of the role of this pathway in a physiological context revealed that the loss of FBXO10 or expression of prenylation-deficient-FBXO10(C953S) inhibited PGAM5 degradation, disrupted mitochondrial homeostasis, and impaired myogenic differentiation of human iPSCs and murine myoblasts. Our studies identify a mechanism for selective E3-ligase mediated regulation of mitochondrial membrane proteostasis and metabolic health, potentially amenable to therapeutic intervention.

cell biology↗

bioRxiv2022

Ubiquitinome analysis of articular cartilage post mechanical injury reveals a differential ubiquitination pattern of a subset of DUBs and proteins linked to the ERAD cellular response

Understanding how connective tissue cells respond to mechanical stimulation is important to human health and disease processes in musculoskeletal diseases. Injury to articular cartilage is a key risk factor in predisposition to osteoarthritis. Here we identified a ubiquitin signature that is unique to injured articular cartilage tissue (the "injury ubiquitinome"). A total of 408 ubiquitinated peptides mapped to 114 proteins were identified, with an enrichment of ubiquitinated peptides of proteins involved in protein processing in the endoplasmic reticulum(ER), also known as the ER-associated degradation(ERAD) response, including YOD1, BRCC3, ATXN3 and USP5 as well as the ER stress regulators, RAD23B, VCP/p97 and Ubiquilin 1. Enrichment of these proteins suggested an injury-induced ER stress response and, for instance, ER stress markers DDIT3/CHOP and BIP/GRP78 were upregulated following cartilage injury on the protein and gene expression levels. Similar ER stress induction was also observed in response to tail fin injury in zebrafish larvae, suggesting a generic response to tissue injury. Furthermore, a rapid increase in global DUB activity following injury and significant activity in human osteoarthritic cartilage was observed using DUB specific activity probes. Inhibition of DUBs using a broad-spectrum inhibitor caused a reduction in the injury-induced inflammatory response in a zebrafish tail fin injury model. These results implicate the involvement of ubiquitination events and activation of a set of DUBs and ER stress regulators in cellular responses to cartilage tissue injury and osteoarthritis. This link through the ERAD pathway makes this protein set attractive for further investigation in in vivo models of tissue injury and for targeting in osteoarthritis and related musculoskeletal diseases.

biochemistry↗

bioRxiv2021

Variants in ALDH1A2 reveal an anti-inflammatory role for retinoic acid and a new class of disease-modifying drugs in osteoarthritis

Over 40% of individuals will develop osteoarthritis (OA) during their lifetime, yet there are currently no licensed disease modifying treatments for this disabling condition. Common polymorphic variants in ALDH1A2, that encodes the key enzyme in the synthesis of all-trans retinoic acid (atRA), have been associated with severe hand OA. In this study, we sought to elucidate the biological significance of this association. We first confirmed that ALDH1A2 risk variants were associated with hand OA in UK Biobank. Articular cartilage was acquired from 33 consenting individuals with hand OA at the time of routine hand OA surgery. They were stratified by genotype and RNA sequencing performed. A reciprocal relationship between ALDH1A2 mRNA and inflammatory genes was observed. Articular cartilage injury up-regulates similar inflammatory genes by a process that we have previously termed mechanoflammation, and which we believe is a primary driver of OA. Cartilage injury was also associated with a concomitant drop in atRA-dependent genes, indicative of cellular atRA levels, and both responses to injury were reversed using talarozole, a retinoic acid metabolism blocking agent (RAMBA). Suppression of mechanoflammation by talarozole was mediated by a peroxisome proliferator activated receptor (PPAR)-{gamma} dependent mechanism. Talarozole, delivered by minipump, was able to suppress mechano-inflammatory genes in articular cartilage in vivo 6h after mouse knee joint destabilization, and reduced cartilage degradation and osteophyte formation after 4 weeks. These data show that boosting atRA suppresses mechanoflammation in the articular cartilage in vitro and in vivo, and identifies RAMBAs as potential disease modifying drugs in OA. One Sentence SummaryAnalysis of hand OA cartilage stratified by ALDH1A2 polymorphic variants reveals a targetable, anti-inflammatory role for retinoic acid in OA.

molecular biology↗

bioRxiv2021

A de novo paradigm for male infertility

IntroductionDe novo mutations (DNMs) are known to play a prominent role in sporadic disorders with reduced fitness1. We hypothesize that DNMs play an important role in male infertility and explain a significant fraction of the genetic causes of this understudied disorder. To test this hypothesis, we performed trio-based exome-sequencing in a unique cohort of 185 infertile males and their unaffected parents. Following a systematic analysis, 29 of 145 rare protein altering DNMs were classified as possibly causative of the male infertility phenotype. We observed a significant enrichment of Loss-of-Function (LoF) DNMs in LoF-intolerant genes (p-value=1.00x10-5) as well as predicted pathogenic missense DNMs in missense-intolerant genes (p-value=5.01x10-4). One DNM gene identified, RBM5, is an essential regulator of male germ cell pre-mRNA splicing2. In a follow-up study, 5 rare pathogenic missense mutations affecting this gene were observed in a cohort of 2,279 infertile patients, with no such mutations found in a cohort of 5,784 fertile men (p-value=0.009). Our results provide the first evidence for the role of DNMs in severe male infertility and point to many new candidate genes affecting fertility.

genetics↗

bioRxiv2020

Repurposing the orphan drug nitisinone to control the transmission of African trypanosomiasis

Tsetse transmit African trypanosomiasis, which is a disease fatal to both humans and animals. A vaccine to protect against this disease does not exist so transmission control relies on eliminating tsetse populations. Although neurotoxic insecticides are the gold standard for insect control, they negatively impact the environment and reduce insect pollinator species. Here we present a promising, environment-friendly alternative that targets insect tyrosine metabolism pathway. A bloodmeal contains high levels of tyrosine, which is toxic to haematophagous insects if it is not degraded. RNAi silencing of either the first two enzymes in the tyrosine degradation pathway (TAT and HPPD) was lethal to tsetse. Furthermore, nitisinone (NTBC), an FDA-approved tyrosine catabolism inhibitor, killed tsetse regardless if the drug was orally or topically applied. However, it did not affect bumblebee survival. A mathematical model shows that NTBC could reduce the transmission of African trypanosomiasis in sub-Saharan Africa, thus accelerating current elimination programmes.

biochemistry↗