Biology subjects

Hers, I.

Publications and source records attributed to Hers, I..

8 recordsLinked to original sources

bioRxiv2026

Recombinant Echis disintegrins reveal distinct inhibitory profiles on platelet aggregation and endothelial cell migration

Disintegrins are snake venom toxins that bind integrins and modulate platelet aggregation and cell migration. Isolation from venom often yields insufficient quantities for comprehensive study, making recombinant expression essential for detailed toxin characterisation. Here, we produced and characterised four disintegrins from Echis coloratus and Echis ocellatus in Escherichia coli. These homologous proteins contain distinct integrin-binding motifs: EcDis_RGD, EoDis_RGD, EcDis_KGD, and EcDis_VGD. Functional activities were evaluated using human platelet aggregation and endothelial cell scratch wound-healing assays. RGD-containing disintegrins exhibited the strongest inhibition of platelet aggregation, with EcDis_RGD showing the highest potency. The EcDis_KGD disintegrin inhibited platelet aggregation less potently, whereas EcDis_VGD showed no detectable activity in our assays. In endothelial cells, EcDis_RGD disintegrin markedly impaired cell migration, while EoDis_RGD displayed weaker anti-migratory activity. Neither KGD- nor VGD-containing disintegrins significantly affected wound closure. EoDis_RGD exhibited similar antiplatelet activity to the native, venom-purified disintegrin ocellatusin, validating our recombinant expression strategy. However, the corresponding PII-SVMP preparation displayed reduced inhibitory activity, consistent with incomplete generation of fully mature disintegrins species. Our findings demonstrate the importance of both integrin-binding motif identity and surrounding sequence context in determining disintegrin function, and support further use of recombinant toxins in toxinology and as therapeutic lead molecules.

biochemistry↗

bioRxiv2025

Selective degradation of platelet BTK by PROTAC NX-5948 provides antithrombotic benefits without affecting haemostasis

Current antithrombotic therapies are effective in reducing thrombotic events but are limited by their associated risk of bleeding. BTK acts as a key signalling switch that drives platelet activation during thrombosis but is largely dispensable for routine haemostasis. It is an important non-redundant signalling mediator downstream of the GPVI and CLEC-2 receptors, plays a key role in thrombosis with minimal involvement in haemostasis, making it an attractive antithrombotic target. While BTK inhibitors effectively reduce thrombosis, their clinical use has been limited due to off-target effects. Protein degraders may overcome this limitation by enabling the ubiquitin proteasomal system to selectively target and degrade BTK. We here assessed the ability of the BTK degraders NX-2127 and NX-5948, currently in clinical trials for B cell pathologies, to target platelet BTK for degradation. NX-2127 and NX-5948 induced concentration-dependent degradation of BTK in washed platelets, platelet-rich plasma and whole blood. NX-5948 showed no hook effect and outperformed NX-2127 in potency, efficacy, and degradation kinetics. TMT proteomic analysis confirmed selective BTK degradation by NX-5948 with no evidence of major off-target effects. BTK degradation impaired CRP-mediated integrin IIb{beta}3 activation, P-selectin expression, platelet aggregation and in vitro thrombosis, with PAR-1 mediated platelet function being left intact. Dosing mice with NX-5948 led to efficacious degradation of platelet BTK and impaired CRP-, but not thrombin-, mediated ex vivo platelet function. In vivo, arterial thrombosis was markedly reduced, without an increase in bleeding time. Together, these results highlight NX-5948 as a potent, selective BTK degrader with antithrombotic potential and minimal haemostatic impact. Key PointsO_LIThe BTK degrader NX-5948 potently and selectively degrades platelet BTK and suppresses thrombus formation without affecting bleeding. C_LIO_LITargeting BTK degradation offers a new antithrombotic strategy that spares haemostasis and may aid patients intolerant to DAPT. C_LI

cell biology↗

bioRxiv2023

CryoET reveals actin filaments within platelet microtubules

Crosstalk between the actin and microtubule cytoskeletons is essential for many cellular processes. Recent studies have shown that microtubules and F-actin can assemble to form a composite structure where F-actin occupies the microtubule lumen. Whether these cytoskeletal hybrids exist in physiological settings and how they are formed is unclear. Here, we show that the short-crossover Class I actin filament previously identified inside microtubules in human HAP1 cells is cofilin-bound F-actin. Lumenal F-actin can be reconstituted in vitro, but cofilin is not essential. Moreover, actin filaments with both cofilin-bound and canonical morphologies reside within human platelet microtubules under physiological conditions. We propose that stress placed upon the microtubule network during motor-driven microtubule looping and sliding may facilitate the incorporation of actin into microtubules.

cell biology↗

bioRxiv2022

Alterations in platelet proteome signature and impaired platelet integrin αIIbβ3 activation in patients with COVID-19

BackgroundPatients with coronavirus disease-19 (COVID-19) are at increased risk of thrombosis, which is associated with altered platelet function and coagulopathy, contributing to excess mortality. ObjectivesWe aimed to characterise the mechanism of altered platelet function in COVID-19 patients. MethodsThe platelet proteome, platelet functional responses and platelet-neutrophil aggregates were compared between patients hospitalised with COVID-19 and healthy control subjects using Tandem Mass Tag (TMT) proteomic analysis, Western blotting and flow cytometry. ResultsCOVID-19 patients showed a different profile of platelet protein expression (858 altered out of 5773 quantified). Levels of COVID-19 plasma markers were enhanced in COVID-19 platelets. Gene ontology (GO) pathway analysis demonstrated that levels of granule secretory proteins were raised, whereas some platelet activation proteins, such as the thrombopoietin receptor and PKC, were lowered. Basally, COVID-19 platelets showed enhanced phosphatidylserine (PS) exposure, with unaltered integrin IIb{beta}3 activation and P-selectin expression. Agonist-stimulated integrin IIb{beta}3 activation and PS exposure, but not P-selectin expression, were significantly decreased in COVID-19 patients. COVID-19 patients had high levels of platelet-neutrophil aggregates, even under basal conditions, compared to controls. This interaction was disrupted by blocking P-selectin, demonstrating that platelet P-selectin is critical for the interaction. ConclusionsOverall, our data suggests the presence of two platelet populations in patients with COVID-19: one with circulating platelets with an altered proteome and reduced functional responses and another with P-selectin expressing neutrophil-associated platelets. Platelet driven thromboinflammation may therefore be one of the key factors enhancing the risk of thrombosis in COVID-19 patients. Essentials- COVID-19 patient platelet function and platelet proteins were compared with healthy controls - Proteomic analysis of platelets indicated that COVID-19 decreased platelet activation proteins - Agonist induced PS exposure and integrin IIb{beta}3 activation were impaired in COVID-19 - COVID-19 led to maximal levels of P-selectin dependent platelet-neutrophil aggregates

cell biology↗

bioRxiv2022

Chemical degradation of BTK/TEC as a novel approach to inhibit platelet function and thrombosis.

The tyrosine kinase BTK plays an important role in platelet function downstream of GPVI and CLEC2 receptors and has been proposed as a novel target to prevent thrombosis in patients that are at increased risk. However, current clinically approved BTK inhibitors have off target effects and are associated with an increased bleeding risk. In this study, we therefore explored whether BTK can be targeted for degradation in human platelets by using recently developed heterobifunctional molecules that employ the proteasomal system to break down BTK. Here we confirm that human platelets are highly susceptible to BTK degraders with the generic tyrosine kinase degrader TL12-186, and the BTK degraders DD-04-15 and DD-03-171 leading to breakdown of BTK and its closely related kinase TEC, an effect that was prevented by proteasomal inhibitors. Tandem Mass Tag proteomic analysis confirmed high selectivity with TL12-186 degrading BTK/TEC, FAK/PYK2 and FER, whereas DD-04-15 and DD-03-171 degraded BTK/TEC only. GPVI-mediated platelet integrin IIb{beta}3 activation, P-selectin expression, and phosphatidyl-serine exposure were largely impaired upon BTK/TEC degradation, with PAR-1-mediated responses left intact. This is the first study to demonstrate that chemical protein degraders can be successfully employed in anucleate human platelets to modulate their function.

cell biology↗

bioRxiv2021

Platelet generation from circulating megakaryocytes is triggered in the lung vasculature

Platelets, small hemostatic blood cells, are derived from megakaryocytes, although the generation process is not clear. Only small numbers of platelets have been produced in systems outside the body, where bone marrow and lung are proposed as sites of platelet generation. Here we show that perfusion of megakaryocytes ex vivo through the mouse lung vasculature generates very large numbers of platelets, up to 3,000 per megakaryocyte. Despite their large size, megakaryocytes were able repeatedly to passage through the lung vasculature, leading to enucleation and fragmentation to generate platelets intravascularly. Using the ex vivo lung and a novel in vitro microfluidic chamber we determined the contributions of oxygenation, ventilation and endothelial cell health to platelet generation, and showed a critical role for the actin regulator TPM4. One-Sentence SummaryMegakaryocytes form platelets intravascularly in the lung, dependent upon oxygenation, endothelium and megakaryocyte TPM4

physiology↗

bioRxiv2021

A role for SHARPIN in platelet linear protein ubiquitination and function

SHARPIN (Src homology 3 and multiple ankyrin repeat domains protein (SHANK)- associated RH domain-interacting protein) as part of the linear ubiquitin chain assembly complex (LUBAC) catalyses the addition of linear (Met1-linked) ubiquitin chains to substrates. As part of this complex SHARPIN acts as a multi-functional modulator of immune/inflammatory responses through regulation of NfkB activation. In addition, SHARPIN can act as a negative regulator of integrin function. Despite platelets being anucleate cells several studies have determined potential roles for both ubiquitination and NfkB in regulating platelet function. However, little is known about either linear ubiquitination and/or SHARPIN in mouse platelets. In this study, we evaluated platelet function in mice with impaired SHARPIN expression. We confirmed that SHARPIN was expressed in platelets from wild-type mice but not in mice homozygous for SHARPINcpdm allele (cpdm/cpdm) and that this correlated with a reduction in linear ubiquitination. Platelet function in response to thrombin was unaffected. In contrast, CRP-XL-and U46619-mediated platelet responses and thrombus formation under flow on a collagen-coated surface were significantly reduced in the cpdm/cpdm mice. This was associated with impaired U46619-mediated intracellular signalling as well as a reduction in CRP-mediated ERK phosphorylation. Despite the reported role for Nf{kappa}B in regulating platelet function, inhibiting I{kappa}B phosphorylation did not recapitulate the cpdm/cpdm phenotype. Together, these data indicate that the lack of SHARPIN and linear ubiquitination results in impaired thrombosis and platelet functional responses to CRP and U46619. This phenotype is independent of Nf{kappa}B pathway inhibition but may involve alternative signalling pathways regulated by linear ubiquitination. Key PointsO_LISHARPIN plays an essential role in platelet linear protein ubiquitination and CRP and U46619-mediated platelet function C_LIO_LIIn vitro thrombosis is significantly impaired in SHARPIN deficient mice C_LI

cell biology↗

bioRxiv2018

Hypothesis-free analysis of deep vein thrombosis aetiology: a Mendelian randomization study

BackgroundDeep vein thrombosis (DVT) is the formation of a thrombus/clot in the deep veins, when part of this clot breaks off it can travel to the lungs, resulting in pulmonary embolism. These two conditions together are known as venous thromboembolism (VTE), a leading cause of death and disability worldwide. Despite the prevalence of VTE, we do not fully understand what causes it and it is often overlooked as a major public health problem. Confirming and identifying risk factors associated with DVT is likely to lead to a reduction in the incidence, morbidity and mortality of VTE especially where these risk factors are modifiable. We can do this, by exploiting the availability of summary genetic data from genome-wide association studies (GWAS) of numerous phenotypes, including DVT, which permits hypothesis-free causal inference.\n\nObjectivesTo identify novel risk factors for DVT and to assess the causality of factors previously shown to be associated with DVT.\n\nMethodsTwo-sample Mendelian randomization (MR) was performed using summarised genetic data. Inverse variance weighted (IVW) estimates were calculated and validated by additional methods more robust to horizontal pleiotropy (MR Egger, simple mode, weighted mode, and weighted median). Bidirectional and heterogeneity sensitivity analyses were performed to further evaluate our findings.\n\nResultsForty-seven exposures passed an exposure-exposure correlation-adjusted Bonferroni P-value threshold (5.43E-05). These included previously hypothesised risk factors for DVT (e.g. body mass index, varicose veins, height, hyperthyroidism) and novel associations (e.g. prospective memory, basal metabolic rate).\n\nConclusionOur analyses confirmed causal associations of risk factors previously associated with DVT and highlighted several novel risk factors for the disease. Our study demonstrates the utility of using a hypothesis free Mendelian randomization approach for the identification of novel disease risk factors.

epidemiology↗