Biology subjects

Ong, H.

Publications and source records attributed to Ong, H..

6 recordsLinked to original sources

bioRxiv2026

CD36 phosphorylation alters the thrombospondin binding site and reduces internal cavity accessibility and volume

The cluster of differentiation 36 (CD36) is a membrane protein with broad physiological roles in health and disease, and its function is regulated in part by phosphorylation. Experimental evidence shows that phosphorylation of Thr92 reduces CD36 affinity for thrombospondin-1 (TSP-1), binding of which initiates antiangiogenic signaling, whereas phosphorylation of Ser237 decreases CD36-mediated fatty acid uptake, with implications for energy metabolism. However, the only available crystal structure of CD36 lacks phosphorylation, and the molecular mechanisms by which phosphorylation regulates CD36 function remain largely unknown. This study provides an atomically detailed computational characterization of CD36 in unphosphorylated and dual phosphorylated states, using molecular dynamics simulations with a total sampling time of 30 microseconds in combination with Markov state models. We present, to our knowledge, the first evidence of a cryptic pocket on CD36 surface that is formed by phosphorylation. This cryptic surface pocket and a loop spanning residues 121-131 form a high affinity binding site for TSP-1 derived ligands, shifting their binding away from the canonical site. We propose that this altered binding provides a molecular basis for the disruption of antiangiogenic signaling upon CD36 phosphorylation. Additionally, our data indicate that, phosphorylation increases helicity and compaction within the helix-loop region spanning residues 296-331, narrowing one of the entrances to the internal cavity and reducing its overall volume. These conformational changes provide a potential mechanistic explanation for the decrease in fatty acid uptake upon CD36 phosphorylation. Our findings provide structural insights that may inform the future design of CD36 modulators and emphasize the importance of targeting phosphorylation induced CD36 conformations in angiogenic and metabolic diseases.

biophysics↗

bioRxiv2025

Cyclic azapeptide cluster of differentiation-36 receptor modulator attenuates left ventricular injury and temporarily reduces long-chain fatty acid accumulation after myocardial ischemia-reperfusion in mice

Ischemic heart disease remains a leading global cause of death. We investigated the cardio-protective effects of the selective cluster of differentiation-36 receptor (CD36) modulator azapeptide MPE-298 in a mouse model of myocardial ischemia-reperfusion. Before reperfusion, a single intravenous dose of azapeptide MPE-298 reduced infarct size by 37% and transiently decreased left ventricular (LV) long-chain fatty acid (LCFA) accumulation, independently of saturation status. Metabolomic profiling revealed shifts in amino acids involved in energy production and antioxidant defense. Gene expression analysis showed transient modulation of oxidative stress and inflammation in both heart and adipose tissue. Modulation of CD36 by azapeptide MPE-298 exhibited therapeutic potential for treating acute myocardial ischemia and reperfusion by supporting metabolic recovery and limiting excess LCFA uptake. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=171 SRC="FIGDIR/small/674351v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@11aa899org.highwire.dtl.DTLVardef@132fc5borg.highwire.dtl.DTLVardef@55c32forg.highwire.dtl.DTLVardef@81585f_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2025

UNWANTED AXON GROWTH: PTEN AND THE SUPPRESSION OF AXON PLASTICITY IN ADULT NERVES

In adults, peripheral nerves comprise bundles of disseminated motor, sensory and autonomic axons that are considered stable neuroanatomical units. The only exceptions to this established wiring are very distal terminal branches in target organs, such as skin. Here we provide a remarkable deviation from this state of affairs in the peripheral nerves of mice with a conditional knockout of sensory neuron PTEN (phosphatase and tensin homolog deleted on chromosome ten). PTEN is normally expressed in adult sensory neurons, particularly small IB4 nonpeptidergic subtypes and its knockdown after injury or during experimental diabetes improves axon regrowth. We studied Advillin Cre;PTEN null mice lacking PTEN in their sensory neurons. As might be expected, their harvested and cultured DRG neurons displayed enhanced neurite outgrowth in vitro. In vivo, these mice were healthy and had a normal sensory behavioural phenotype. However, the nerves of mice lacking sensory neuron PTEN were highly abnormal, with augmented clusters of small myelinated and unmyelinated axons populating endoneurial fascicles of their peripheral nerve trunks. The axon clusters did not disrupt normal fascicular anatomy but invested the epidermis with greater axon numbers. Within endoneurial fascicles, supernumerary axons formed regenerative units and expressed ongoing growth markers, unlike normal adult axons. This was not accompanied by rises in dorsal root ganglia (DRG) neuron numbers, indicating enhanced distal sprouting from parent neurons. Additionally, sprouting axons were electrophysiologically intact, generating rises in the amplitudes of sensory nerve action potentials. Despite this extensive regenerative activity of intact nerves, regeneration indices after superimposed injury were only modestly enhanced or unchanged. This unusual behaviour of adult sensory axons lacking a single growth-suppressive molecule may identify insights into what molecular constraints the nervous system normally utilizes to suppress inappropriate plasticity.

neuroscience↗

bioRxiv2021

An invariant Trypanosoma vivax vaccine antigen inducing protective immunity

Trypanosomes are protozoan parasites that cause infectious diseases including human African trypanosomiasis (sleeping sickness), and nagana in economically-important livestock animals1,2. An effective vaccine against trypanosomes would be an important control tool, but the parasite has evolved sophisticated immunoprotective mechanisms including antigenic variation3 that present an apparently insurmountable barrier to vaccination. Here we show using a systematic genome-led vaccinology approach4 and a murine model of Trypanosoma vivax infection5 that protective invariant subunit vaccine antigens can be identified. Vaccination with a single recombinant protein comprising the extracellular region of a conserved cell surface protein localised to the flagellum membrane termed "invariant flagellum antigen from T. vivax" (IFX) induced long-lasting protection. Immunity was passively transferred with immune serum, and recombinant monoclonal antibodies to IFX could induce sterile protection and revealed multiple mechanisms of antibody-mediated immunity, including a major role for complement. Our discovery identifies a vaccine candidate for an important parasitic disease that has constrained the socioeconomic development of sub-Saharan African countries6 and challenges long-held views that vaccinating against trypanosome infections cannot be achieved.

microbiology↗

bioRxiv2020

Poly(ADP-ribose) potentiates ZAP antiviral activity

Zinc-finger antiviral protein (ZAP), also known as poly(ADP-ribose) polymerase 13 (PARP13), is an antiviral factor that selectively targets viral RNA for degradation. ZAP is active against both DNA and RNA viruses, including important human pathogens such as hepatitis B virus and type 1 human immunodeficiency virus (HIV-1). ZAP selectively binds CpG dinucleotides through its N-terminal RNA-binding domain, which consists of four zinc fingers. ZAP also contains a central region that consists of a fifth zinc finger and two WWE domains. Through structural and biochemical studies, we found that the fifth zinc finger and tandem WWEs of ZAP combine into a single integrated domain that binds to poly(ADP-ribose) (PAR), a cellular polynucleotide. PAR binding is mediated by the second WWE module of ZAP and likely involves specific recognition of iso(ADP-ribose), a repeating structural unit of PAR. Mutation of the putative iso(ADP-ribose) binding site in ZAP abrogates the interaction in vitro and diminishes ZAP activity against a CpG-rich HIV-1 reporter virus. In cells, PAR facilitates formation of non-membranous sub-cellular compartments such as DNA repair foci, spindle poles and cytosolic RNA stress granules. Our results suggest that ZAP-mediated viral mRNA degradation is facilitated by PAR, and provides a biophysical rationale for the reported association of ZAP with RNA stress granules.

microbiology↗

bioRxiv2020

Origin and evolution of the Zinc Finger Antiviral Protein

The human zinc finger antiviral protein (ZAP) recognizes RNA by binding to CpG dinucleotides. Mammalian transcriptomes are CpG-poor, and ZAP may have evolved to exploit this feature to specifically target non-self viral RNA. Phylogenetic analyses reveal that ZAP and its paralogue PARP12 share an ancestral gene that arose prior to extensive eukaryote divergence, and the ZAP lineage diverged from the PARP12 lineage in tetrapods. Notably, The CpG content of modern eukaryote genomes varies widely, and ZAP-like genes arose subsequent to the emergence of CpG-suppression in vertebrates. Human PARP12 exhibited no antiviral activity against wild type and CpG-enriched HIV-1, but ZAP proteins from several tetrapods had antiviral activity when expressed human cells. In some cases, ZAP antiviral activity required a TRIM25 protein from the same or a related species, suggesting functional co-evolution of these genes. Indeed, a hypervariable sequence in the N-terminal domain of ZAP contributed to species-specific TRIM25 dependence in antiviral activity assays. Crosslinking immunoprecipitation coupled with RNA sequencing revealed that ZAP proteins from human, mouse, bat and alligator exhibit a high degree of CpG-specificity, while some avian ZAP proteins appear more promiscuous. Together, these data suggest that the CpG-rich RNA directed antiviral activity of ZAP-related proteins arose in tetrapods, subsequent to the onset of CpG suppression in certain eukaryote lineages, with subsequent species-specific adaptation of cofactor requirements and RNA target specificity. Author SummaryTo control viral infections, cells have evolved a variety of mechanisms that detect, modify and sometimes eliminate viral components. One of such mechanism is the Zinc Finger Antiviral Protein (ZAP) which binds RNA sequences that are rich in elements composed of a cytosine followed by a guanine. Selection of viral RNA can only be achieved because such elements are sparse in RNAs encoded by human genes. Here, we traced the molecular evolution of ZAP. We found that ZAP and a closely related gene, PARP12, originated from the same ancestral gene that existed in a predecessor of vertebrates and invertebrates. We found that ZAP proteins from mammals, birds and reptiles have antiviral activity but only in the presence of a co-factor, TRIM25, from the same species. ZAP proteins from birds were particularly interesting since they demonstrated a broader antiviral activity, primarily driven by relaxed requirement for cytosine-guanine. Our findings suggest that viruses that infect birds - which are important vectors for human diseases - are under differential selective pressures and this property may influence the outcome of interspecies transmission.

microbiology↗