Biology subjects

Townsend, D.

Publications and source records attributed to Townsend, D..

5 recordsLinked to original sources

bioRxiv2024

Differential Effectiveness of Poloxamer 188 in Dystrophic Cardiomyopathy Reveals Complex Pathophysiology.

Synthetic membrane stabilizers, such as poloxamer 188 (P188), have great promise in the treatment of Duchenne muscular dystrophy and other diseases associated with disrupted membranes. The aim of this study was to assess the efficacy of P188 to limit myocardial damage in models of muscular dystrophy subjected to highly injurious stress. These studies use male and female mdx and {beta}-sarcoglycan null ({beta}-SG-/-) mice subjected to an isoproterenol stress protocol in the presence or absence of P188. We show that P188 provides a significant level of protection to male mdx hearts from the isoproterenol induced injury. Surprisingly, we find that P188 has no protective actions in female mdx mice or in {beta}-SG-/- mice of either sex. These results suggest that the mechanism of action of P188 is more complicated than previously thought. The presence of sex differences in the absence of dystrophin is not consistent with a model of P188 working by biophysical restoration of membrane integrity. Furthermore, the absence of protective effects of P188 in {beta}-SG-/- myocardium indicates that there are important differences in the mechanisms of membrane damage in hearts lacking dystrophin and hearts lacking the sarcoglycan complex. Developing a better understanding of these differences will be important in the development of therapies for dystrophic cardiomyopathy and other forms of heart disease.

physiology↗

bioRxiv2021

Characterisation of the Ubiquitin-ESCRT pathway in Asgard archaea sheds new light on origins of membrane trafficking in eukaryotes

The ESCRT machinery performs a critical role in membrane remodelling events in all eukaryotic cells, including in membrane trafficking, membrane repair, cytokinetic abscission, in viral egress, and in the generation of extracellular vesicles. While the machinery is complex in modern day eukaryotes, where it comprises dozens of proteins, the system has simpler and more ancient origins. Indeed, homologues of ESCRT-III and the Vps4 ATPase, the proteins that execute the final membrane scission reaction, play analogous roles in cytokinesis and potentially in extracellular vesicle formation in TACK archaea where ESCRT-I and II homologues seem to be absent. Here, we explore the phylogeny, structure, and biochemistry of homologues of the ESCRT machinery and the associated ubiquitylation system found in genome assemblies of the recently discovered Asgard archaea. In these closest living prokaryotic relatives of eukaryotes, we provide evidence for the ESCRT-I and II sub-complexes being involved in the ubiquitin-directed recruitment of ESCRT-III,_as it is in eukaryotes. This analysis suggests a pre-eukaryotic origin for the Ub-coupled ESCRT system and a likely path of ESCRT evolution via a series of gene duplication and diversification events.

cell biology↗

bioRxiv2021

Peptide-based inhibitors of Tau aggregation as a potential therapeutic for Alzheimer's disease and other Tauopathies

There are currently no disease altering drugs available for Tauopathies such as Alzheimers disease, which alone is predicted to affect ~88 million people worldwide by 2050. As Tau aggregation underpins its toxicity, aggregation inhibitors are likely to have disease-modifying potential. Guided by in-silico mutagenesis studies, we developed a potent retro-inverso peptide inhibitor of Tau aggregation, RI-AG03 [Ac-rrrrrrrrGpkyk(ac)iqvGr-NH2], based on the 306VQIVYK311 hotspot. Aggregation of recombinant Tau was reduced by >90% with equimolar RI-AG03 and no fibrils were observed by EM. When added during the growth phase, RI-AG03 blocked seeded aggregation. Fluorescein-tagged RI-AG03 efficiently penetrated HEK-293 cells over 24 hours and was non-toxic at doses up to 30 M. In transgenic Drosophila, RI-AG03 significantly improves neurodegenerative and behavioural phenotypes caused by expression of human Tau. Collectively this shows that RI-AG03 can effectively reduce Tau aggregation in vitro and block aggregation-dependent phenotypes in vivo, raising possibilities for exploring its translational potential.

neuroscience↗

bioRxiv2019

Integrase-RNA interactions underscore the critical role of integrase in HIV-1 virion morphogenesis

A large number of HIV-1 integrase (IN) alterations, referred to as class II substitutions, exhibit pleotropic effects during virus replication. However, the underlying mechanism for the class II phenotype is not known. Here we demonstrate that all tested class II IN substitutions compromised IN-RNA binding in virions by one of three distinct mechanisms: i) markedly reducing IN levels thus precluding formation of IN complexes with viral RNA; ii) adversely affecting functional IN multimerization and consequently impairing IN binding to viral RNA; iii) directly compromising IN-RNA interactions without substantially affecting IN levels or functional IN multimerization. Inhibition of IN-RNA interactions resulted in mislocalization of the viral ribonucleoprotein complexes outside the capsid lattice, which led to premature degradation of the viral genome and IN in target cells. Collectively, our studies uncover causal mechanisms for the class II phenotype and highlight an essential role of IN-RNA interactions for accurate virion maturation.

microbiology↗

bioRxiv2019

Acute myocardial injury in mdx hearts ameliorated by ARB but not ACE inhibitor treatment

Duchenne muscular dystrophy (DMD) is a devastating muscle disease that afflicts males due to the loss of the protein dystrophin, resulting in muscle deterioration and cardiomyopathy. Dystrophins absence causes increased membrane fragility, myocyte death, and tissue remodeling. Inhibition of angiotensin signaling with ACE inhibitors or angiotensin receptor blockers (ARBs) is a mainstay of DMD therapy, with clinical guidelines recommending starting one of these therapies by the age of 10 to address cardiomyopathy.\n\nUsing the mdx mouse model of DMD, we previously showed that isoproterenol causes extensive damage in dystrophic hearts, and treatment with the ARB losartan starting only 1 hour before isoproterenol dramatically reduced this myocardial injury. In the present study, we probed whether ACE inhibitors, which are more frequently prescribed, can deliver similar protection. Surprisingly, lisinopril treatment initiated 1 hour before isoproterenol failed to demonstrate any effect on injury in mdx hearts. Further, with a 2-week pretreatment, only losartan significantly lowered mdx cardiac injury, without any benefit associated with lisinopril treatment. These results confirm the ability of ARBs, but not ACE inhibitors, to prevent acute injury in mouse hearts, and prompt the question whether ARBs should be more frequently used for DMD cardiomyopathy because of these potential protective actions.

physiology↗