Biology subjects

Philip, N.

Publications and source records attributed to Philip, N..

7 recordsLinked to original sources

bioRxiv2025

Na+/H+ Exchanger Isoform 1 Regulates Apoptosis Susceptibility in Pulmonary Arterial Smooth Muscle from the Sugen/Hypoxia model of Pulmonary Hypertension

Pulmonary hypertension (PH) is characterized by vascular remodeling driven in part by apoptosis-resistant pulmonary arterial smooth muscle cells (PASMCs). Na/H exchanger isoform 1 (NHE1) regulates intracellular pH and plasma membrane cytoskeleton anchoring, influencing PASMC migration and proliferation, but the role of NHE1 in apoptosis remains unclear. NHE activity and NHE1 surface expression were increased in PASMCs from the Sugen/Hypoxia (SuHx) rat model compared to controls. Despite increased endoplasmic reticulum (ER) stress at baseline, SuHx PASMCs were resistant to apoptosis following H2O2 challenge. Pharmacological inhibition of NHE activity with ethyl-isopropyl amiloride (EIPA) and silencing with siRNA restored apoptosis in SuHx PASMCs. Conversely, NHE1 overexpression in control PASMCs conferred apoptosis resistance. Expression of mutant NHE1 constructs lacking ion translocation or binding to the adaptor protein, ezrin, also reduced H2O2-induced apoptosis. Mechanistically, apoptotic stimulation with H2O2 increased p38 phosphorylation in PASMCs from control, but not SuHx, rats, indicating impaired activation of this pro-apoptotic pathway. NHE1 suppression via EIPA or siRNA restored p38 phosphorylation in SuHx PASMCs, while overexpression of NHE1 (wild-type or mutants) suppressed p38 activation following apoptotic stimulation. Inhibition of p38 with SB203580 prevented the pro-apoptotic effect of EIPA, validating a role for p38 signaling in NHE1-mediated apoptosis resistance in SuHx PASMCs. These findings identify NHE1 as necessary and sufficient for PASMC apoptosis resistance in PH, by a mechanism independent of ion transport or ezrin-binding functions but involving suppression of p38 phosphorylation. Targeting NHE1-dependent pathways may restore PASMC apoptosis and offer a novel therapeutic strategy to reverse pulmonary vascular remodeling in PH.

physiology↗

bioRxiv2025

A divergent cyclic nucleotide binding protein promotes Plasmodium ookinete infection of the mosquito

Colonisation of the mosquito by the malarial parasite is critically reliant on the invasive ookinete stage. Ookinete invasion of mosquito is coordinated by the apical complex, a specialised parasite structure containing components for secretion, attachment and penetration. While studies have investigated cytoskeletal and secretory elements, it is currently unknown if signalling modules are present or functional at the apical complex. Here we elucidate the role of a cryptic cyclic nucleotide binding protein which we name CBP-O. PbCBP-O showed a marked localisation to the ookinete apex and disruption of the protein severely compromised ookinete invasion of mosquitos. Domain dissection analysis revealed that the N- and C-termini have distinct functions. Intriguingly, PbCBP-O exhibits dual binding specificity to both cGMP and cAMP. Our findings suggest the apical tip of the ookinete is a platform to transduce cyclic nucleotide signals essential for malaria parasite transmission. Author summaryMalaria parasites complete their life-cycle within mammalian and mosquito hosts requiring specialised forms to invade and establish infection in host tissue. In order to transmit to the mosquito, the parasite forms a motile ookinete that uses the apical end to attach and penetrate the mosquito midgut membrane. Previous studies have identified several proteins localised to the apex of the ookinete. However, functions of many of these proteins are unknown. Here, we dissect the role of a putative cyclic nucleotide binding protein, CBP-O, in establishing ookinete infection within the mosquito. We discovered that in the absence of the protein, efficiency of transmission is significantly compromised. Interestingly the ability of ookinetes to move was not affected, but the parasites were unable to pass through the midgut membrane. We also reveal that both N- and C-terminal domains of the protein perform distinct functions and are both required for parasite transmission. Sequence and spatial conservation of the protein across the phylum Apicomplexa suggests an equivalent and crucial function of CBP-O in these parasites.

microbiology↗

bioRxiv2024

Non-invasive Ultrasound Deep Neuromodulation of the Human Nucleus Accumbens Increases Win-Stay Behaviour

Precisely neuromodulating deep brain regions could bring transformative advancements in both neuroscience and treatment. We demonstrate that non-invasive transcranial ultrasound stimulation (TUS) can selectively modulate deep brain activity and affect learning and decision making, comparable to deep brain stimulation (DBS). We tested whether TUS could causally influence neural and behavioural responses by targeting the nucleus accumbens (NAcc) using a reinforcement learning task. Twenty-six healthy adults completed a within-subject TUS-fMRI experiment with three conditions: TUS to the NAcc, dorsal anterior cingulate cortex (dACC), or Sham. After TUS, participants performed a probabilistic learning task during fMRI. TUS-NAcc altered BOLD responses to reward signals in the NAcc and surrounding areas. It also affected reward-related features, including win-stay strategy use, learning rate following rewards and learning curves. DBS-NAcc perturbed the same features, confirming target engagement. These findings establish TUS as a viable approach for non-invasive deep-brain neuromodulation.

neuroscience↗

bioRxiv2023

Macrophages sense ECM mechanics and growth factor availability through cytoskeletal remodeling to regulate their tissue repair program

Tissue resident macrophages play important roles in tissue homeostasis and repair. However, how macrophages monitor and maintain tissue integrity is not well understood. The extracellular matrix (ECM) is a key structural and organizational component of all tissues. Here, we find that macrophages sense the mechanical properties of the ECM in order to regulate a specific tissue repair program. We show that macrophage mechanosensing is mediated by cytoskeletal remodeling and can be performed in three-dimensional environments through a non-canonical, integrin-independent mechanism analogous to amoeboid migration. We find that these cytoskeletal dynamics also integrate biochemical signaling by CSF1 and ultimately regulate chromatin accessibility to control the mechanosensitive gene expression program. This study suggests a distinct mode of ECM mechanosensing and growth factor signaling through which macrophages may regulate tissue repair and fibrosis.

immunology↗

bioRxiv2021

MK2 Expression Promotes Non-Small Cell Lung Cancer Cell Death and Predicts Survival

Non-small cell lung cancers demonstrate intrinsic resistance to cell death even in response to chemotherapy. Previous work suggested that defective nuclear translocation of active caspase 3 may play a role in resistance to cell death. Separately, our group has identified that mitogen activated protein kinase activated protein kinase 2 (MK2) is required for nuclear translocation of active caspase 3 in the execution of apoptosis. This study demonstrates a relatively low expression of MK2 in non-small cell lung carcinoma cell lines compared to small cell carcinoma cell lines. Further, overexpression of MK2 in non-small cell lung carcinoma cell lines results in increased caspase 3 activity and caspase 3 mediated cell death. Higher MK2 transcript levels were observed in patients with earlier-stage non-small cell lung cancer. Higher expression of MK2 is associated with better survival in patients with early stage non-small cell lung cancer across two independent clinical datasets. Using data sets spanning multiple cancer types, we observed improved survival with higher MK2 expression was unique to lung adenocarcinoma. Mechanistically, MK2 promotes nuclear translocation of caspase 3 leading to PARP1 cleavage and execution of cell death. While MK2 can directly phosphorylate caspase 3, neither phosphorylation status of caspase 3 nor the kinase activity of MK2 impacts caspase 3 activation, nuclear translocation and execution of cell death. Rather, a non-kinase function of MK2, specifically trafficking via its nuclear localization sequence, is required for caspase 3 mediated cell death. In summary this study highlights the importance of a non-enzymatic function of MK2 in the execution of apoptosis, which may be leveraged in the adjunctive treatment of NSCLC or other conditions where regulation of apoptosis is crucial.

cancer biology↗

bioRxiv2019

Zygote morphogenesis but not the establishment of cell polarity in Plasmodium berghei is controlled by the small GTPase, RAB11A

Plasmodium species are apicomplexan parasites whose zoites are polarized cells with a marked apical organisation where the organelles associated with host cell invasion and colonization reside. Plasmodium gametes mate in the mosquito midgut to form the spherical and presumed apolar zygote that morphs during the following 24 hours into a polarized, elongated and motile zoite form, the ookinete. Endocytosis-mediated protein transport is generally necessary for the establishment and maintenance of polarity in epithelial cells and neurons, and the small GTPase RAB11A is an important regulator of protein transport via recycling endosomes. PbRAB11A is essential in blood stage asexual of Plasmodium. Therefore, a promoter swap strategy was employed to down-regulate PbRAB11A expression in gametocytes and zygotes of the rodent malaria parasite, Plasmodium berghei which demonstrated the essential role of RAB11A in ookinete development. The approach revealed that lack of PbRAB11A had no effect on gamete production and fertility rates however, the zygote to ookinete transition was almost totally inhibited and transmission through the mosquito was prevented. Lack of PbRAB11A did not prevent meiosis and mitosis, nor the establishment of polarity as indicated by the correct formation and positioning of the Inner Membrane Complex (IMC) and apical complex. However, morphological maturation was prevented and parasites remained spherical and immotile and furthermore, they were impaired in the secretion and distribution of microneme cargo. The data are consistent with the previously proposed model of RAB11A endosome mediated delivery of plasma membrane in Toxoplasma gondii if not its role in IMC formation and implicate it in microneme function. Author SummaryAccording to the WHO there was estimated to be over 200 million cases of malaria in 2017 and nearly half a million deaths. The disease is caused by specific species of Plasmodium which are passed between human hosts by a mosquito vector. In order to transmit through the mosquito the single-celled parasite undergoes many developmental changes as it morphs from non-motile blood forms to become a polarised and motile ookinete in the mosquito midgut. Transport of proteins within the cell during these critical morphological transitions relies on specific endosome vesicles to correctly target proteins within the parasite. We investigated the role of the RAB11A protein which is known to be involved in endosomal vesicle targeting to generate cellular polarity in other organisms. Because RAB11A is also essential for parasite growth in the mammalian host we used a promoter swap system to specifically switch off RAB11A in the sexual transmission stages. In the absence of RAB11A parasites were unable to form elongated, motile ookinetes and were unable to pass through the mosquito. Interestingly the parasites were able to form some of the (polarising) structures specific to ookinetes however full morphological transformation did not occur and the parasites were not motile. We show that although proteins are still delivered to the parasite surface, secretion is impaired and that the mutant parasites are smaller despite obvious microtubule formation implying that there is a deficit in delivery of membrane to the surface.

cell biology↗

bioRxiv2017

A framework to identify modifier genes in patients with Phelan-McDermid syndrome

Phelan-McDermid syndrome (PMS) is characterized by a variety of clinical symptoms with heterogeneous degrees of severity, including intellectual disability, speech impairment, and autism spectrum disorders (ASD). It results from a deletion of the 22q13 locus that in most cases includes the SHANK3 gene. SHANK3 is considered a major gene for PMS, but the factors modulating the severity of the syndrome remain largely unknown. In this study, we investigated 85 PMS patients with different 22q13 rearrangements (78 deletions, 7 duplications). We first explored their clinical features and provide evidence for frequent corpus callosum abnormalities. We then mapped candidate genomic regions at the 22q13 locus associated with risk of clinical features, and suggest a second locus associated with absence of speech. Finally, in some cases, we identified additional rearrangements at loci associated with ASD, potentially modulating the severity of the syndrome. We also report the first SHANK3 deletion transmitted to five affected daughters by a mother without intellectual disability nor ASD, suggesting that some individuals could compensate for such mutations. In summary, we shed light on the genotype-phenotype relationship of PMS, a step towards the identification of compensatory mechanisms for a better prognosis and possibly treatments of patients with neurodevelopmental disorders.

genetics↗