Biology subjects

Boecking, T.

Publications and source records attributed to Boecking, T..

9 recordsLinked to original sources

bioRxiv2026

Proteolytic control of the SARS-CoV-2 furin cleavage site defines the phenotypic evolution from the pandemic to endemic state

The successive emergence of SARS-CoV-2 variants with altered tissue tropism has progressively decoupled transmissibility from lower respiratory tract pathogenicity. Omicron lineages transmit exceptionally well whilst limiting severe lung disease. Here, we demonstrate that this phenotype has evolved through two temporally distinct tissue-specific proteolytic controls at the Spike (S) furin cleavage site (FCS). At the virion level, cell-type-dependent furin-mediated FCS hyper-cleavage depletes S in lung but not nasal epithelial cells. At the infected cell membrane during cell-cell spread, TMPRSS2 mediates S FCS cleavage but is negatively regulated in the presence of ACE2. Tissue-specific solute carriers SLC6A19 and SLC6A20 sequester ACE2, thereby relieving inhibition of TMPRSS2 and enabling S FCS cleavage during cell-cell spread. Critically, whilst all SARS-CoV-2 lineages benefit from this latter pathway, Omicron variants have evolved exclusive dependence on it, a strategic consolidation that focuses S proteolytic activation to TMPRSS2 alone. The combined outcomes of S protein regulation across viral and cell membranes reveal how tissue-specific proteolytic optimisation drives Omicron's transmission fitness advantage in the upper respiratory tract but at the cost of heavy attenuation in the lower respiratory tract.

microbiology↗

bioRxiv2026

Allosteric capsid inhibitors and their escape mutants drive HIV-1 sensing

Small-molecule capsid inhibitors suppress HIV-1 infectivity by binding to capsid at the same site as FG motif-bearing host cofactors Sec24C, NUP153, CPSF6 and disordered nucleoporins residing in the nuclear pore complex central channel. We have used rational design to develop inhibitors called "allosteres" that target this pocket and inhibit HIV-1 infectivity. X-ray crystal structures of capsid/inhibitor complexes, reveal allosteric shifts upon inhibitor binding in the capsid C-terminal domain which impact the capsid lattice three-fold symmetry axis. Consistent with an uncoating mechanism, we find that allosteres cause HIV-1 to trigger innate immune response dependent on viral DNA and DNA sensor cGAS. Allosteres exhibit a similar loss of potency against clinically induced Lenacapavir resistance mutants but, strikingly, we find that HIV-1 bearing key resistance mutations induces innate immune activation in the absence of inhibitor. We hypothesise that resistant mutant sensitivity to cGAS contributes to reduction of HIV-1 transmission during Lenacapavir use in prophylaxis. Our work expands the physicochemical space and scaffold range for HIV capsid targeting inhibitors, provides mechanistic details of inhibition and facilitates improved inhibitor design.

microbiology↗

bioRxiv2025

The host protein cyclophilin A inhibits HIV-1 nuclear entry by decreasing capsid elasticity

Binding of the host protein cyclophilin A (CypA) to the HIV-1 capsid exerts a variety of effects on infection, including enhancement of reverse transcription, stabilization of the capsid, and promotion of nuclear entry. For several HIV-1 mutants, CypA binding inhibits nuclear entry by an unknown mechanism. We recently demonstrated that HIV-1 cores are elastic and that HIV-1 mutants with inelastic capsids are impaired for nuclear entry and infection of nondividing cells. Here we show that CypA prevents infection of nondividing cells by such mutants and inhibits their entry into the nucleus. CypA binding to mutant cores further reduced their elasticity in vitro, and this effect was reversed by suppressor mutations that restored nuclear entry. We suggest that HIV-1 nuclear entry involves temporal modulation of capsid elasticity by host proteins prior to and during traversal of the nuclear pore.

microbiology↗

bioRxiv2024

The Human T-cell Leukemia Virus capsid protein is a potential drug target

Human T-cell Leukemia Virus type 1 (HTLV-1) is an untreatable retrovirus that causes lethal malignancies and degenerative inflammatory conditions. Effective treatments have been delayed by substantial gaps in our knowledge of the fundamental virology, especially when compared to the closely related virus, HIV. A recently developed and highly effective anti-HIV strategy is to target the virus with drugs that interfere with capsid integrity and interactions with the host. Importantly, the first in class anti-capsid drug approved, lenacapavir, can provide long-acting pre-exposure prophylaxis. Such a property would provide a means to prevent the transmission of HTLV-1, but its capsid has not previously been considered as a drug target. Here we describe the first high-resolution crystal structures of the HTLV-1 capsid protein, define essential lattice interfaces, and identify a previously unknown ligand-binding pocket. We show that this pocket is essential for virus infectivity, providing a potential target for future anti-capsid drug development.

molecular biology↗

bioRxiv2023

Karyopherin mimicry explains how the HIV capsid penetrates nuclear pores

Summary ParagraphHIV can infect non-dividing cells because the viral capsid can overcome the selective barrier of the nuclear pore complex and deliver the genome directly into the nucleus. Remarkably, the intact HIV capsid is over one thousand times greater than the size-limit prescribed by the nuclear pores diffusion barrier. This barrier is a phase-separated condensate in the central channel of the nuclear pore and is comprised of intrinsically-disordered nucleoporin domains enriched in phenylalanine-glycine (FG) dipeptides. Through multivalent FG-interactions, cellular karyopherins and their bound cargoes solubilise in this phase to drive nucleocytoplasmic transport. By performing an in vitro dissection of the nuclear pore complex, we show that a pocket on the surface of the HIV capsid similarly interacts with FG-motifs from multiple nucleoporins and that this interaction licenses capsids to penetrate nucleoporin condensates. This karyopherin mimicry model resolves a key conceptual challenge for the role of the HIV capsid in nuclear entry, and explains how an exogenous entity much larger than any known cellular cargo can non-destructively breach the nuclear envelope.

biochemistry↗

bioRxiv2022

Pharmacologic hyperstabilisation of the HIV-1 capsid lattice induces capsid failure

The HIV-1 capsid has emerged as a tractable target for antiretroviral therapy. Lenacapavir, developed by Gilead Sciences, is the first capsid-targeting drug approved for medical use. Here we investigate the effect of Lenacapavir on HIV capsid stability and uncoating. We employ a single particle approach that simultaneously measures capsid content release and lattice persistence. We demonstrate that Lenacapavirs potent antiviral activity is predominantly due to lethal hyperstabilisation of the capsid lattice and resultant loss of compartmentalisation. This study highlights that disrupting capsid metastability is a powerful strategy for the development of novel antivirals.

biophysics↗

bioRxiv2022

Rapid exchange of stably bound protein and DNA cargo on a DNA origami receptor

Biomolecular complexes can form stable assemblies yet can also rapidly exchange their subunits to adapt to environmental changes. Simultaneously allowing for both stability and rapid exchange expands the functional capacity of biomolecular machines and enables continuous function while navigating a complex molecular world. Inspired by biology, we design and synthesize a DNA origami receptor that exploits multi-valent interactions to form stable complexes that are simultaneously capable of rapid subunit exchange. The system utilizes a mechanism first outlined in the context of the DNA replisome, known as multi-site competitive exchange, and achieves a large separation of time scales between spontaneous subunit dissociation, which requires days, and rapid subunit exchange, which occurs in minutes. In addition, we use the DNA origami receptor to demonstrate stable interactions with rapid exchange of both DNA and protein subunits, thus highlighting the applicability of our approach to arbitrary molecular cargo; an important distinction with canonical toehold exchange between single-stranded DNA. We expect this study to be the first of many that use DNA origami structures to exploit multi-valent interactions for the design and synthesis of a wide range of possible kinetic behaviors.

synthetic biology↗

bioRxiv2021

Single-molecule analysis of the entire perfringolysin O poreformation pathway

The cholesterol-dependent cytolysin perfringolysin O (PFO) is secreted by Clostridium perfringens as a bacterial virulence factor able to form giant ring-shaped pores that perforate and ultimately lyse mammalian cell membranes. To resolve the kinetics of all steps in the assembly pathway, we have used single-molecule fluorescence imaging to follow the dynamics of PFO on dye-loaded liposomes that lead to opening of a pore and release of the encapsulated dye. Formation of a long-lived membrane-bound PFO dimer nucleates the growth of an irreversible oligomer. The growing oligomer can insert into the membrane and open a pore at stoichiometries ranging from tetramers to full rings ([~]35-mers), whereby the rate of insertion increases linearly with the number of subunits. Oligomers that insert before the ring is complete continue to grow by monomer addition post insertion. Overall, our observations suggest that PFO membrane insertion is kinetically controlled.

biophysics↗

bioRxiv2020

Dynamics of Tpm1.8 domains on actin filaments with single moleculeresolution

Tropomyosins regulate dynamics and functions of the actin cytoskeleton by forming long chains along the two strands of actin filaments that act as gatekeepers for the binding of other actin-binding proteins. The fundamental molecular interactions underlying the binding of tropomyosin to actin are still poorly understood. Using microfluidics and fluorescence microscopy, we observed the binding of fluorescently labelled tropomyosin isoform Tpm1.8 to unlabelled actin filaments in real time. This approach in conjunction with mathematical modeling enabled us to quantify the nucleation, assembly and disassembly kinetics of Tpm1.8 on single filaments and at the single molecule level. Our analysis suggests that Tpm1.8 decorates the two strands of the actin filament independently. Nucleation of a growing tropomyosin domain proceeds with high probability as soon as the first Tpm1.8 molecule is stabilised by the addition of a second molecule, ultimately leading to full decoration of the actin filament. In addition, Tpm1.8 domains are asymmetrical, with enhanced dynamics at the edge oriented towards the barbed end of the actin filament. The complete description of Tpm1.8 kinetics on actin filaments presented here provides molecular insight into actin-tropomyosin filament formation and the role of tropomyosins in regulating actin filament dynamics.

biophysics↗