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Biology subjects

Tulli, L.

Publications and source records attributed to Tulli, L..

2 recordsLinked to original sources

Cancer-associated mutations reconfigure dynamical responses in EGFR kinase

The epidermal growth factor receptor (EGFR) is a tyrosine kinase receptor that plays a fundamental role in regulating cellular proliferation, survival, and differentiation. EGFR's kinase domain catalyses the autophosphorylation that drives downstream signalling and is a known hotspot for cancer-associated mutations. Such substitutions often enhance receptor activation, driving oncogenesis and therapeutic resistance, with major implications for prognosis and treatment choice; consequently, a detailed understanding of this domain's functional dynamics, and how mutations reshape them, is essential. Here, we apply dynamical-nonequilibrium molecular dynamics (D-NEMD) simulations to probe how changes at the ATP-binding site are transmitted throughout the kinase domain, ultimately shaping the behaviour of distal regions in the wild-type protein and in two of the most clinically observed non-small cell lung cancer variants, L858R and L858R+T790M. D-NEMD reveals previously uncharacterised communication networks linking the ATP pocket to key functional motifs, including the P-loop, C-helix, hinge region, activation loop, and F-helix, showing the intricate allosteric connectivity within this domain. Notably, numerous cancer-related mutation sites, despite being distant from the ATP site, map onto or lie close to these communication pathways, indicating that D-NEMD simulations can identify functionally relevant allosteric positions and potential mutation sites in EGFR. Our simulations further reveal that the two variants rewire EGFR's internal signal propagation network in distinct ways: L858R diminishes the transmission of structural changes to distal regions of the C-lobe, whereas introducing T790M in addition to L858R partially restores wild-type-like behaviour through compensatory rerouting of early-stage dynamical pathways.

biochemistry↗

pH-induced structural changes in SARS-CoV-2 spike variants

pH critically influences SARS-CoV-2 infectivity and stability by, for example, triggering pH-dependent conformational changes in the spike glycoprotein that can facilitate membrane fusion and viral entry into host cells. Using the emerging dynamical nonequilibrium molecular dynamics (D-NEMD) simulations approach, we investigated how biologically relevant pH shifts affect the functional dynamics of the fully glycosylated spike from the ancestral, Delta, and Omicron BA.1 variants of concern. For this, over 1100 nonequilibrium simulations were conducted to capture the pH-induced structural and dynamic changes that occur following transitions from physiological to acidic and alkaline conditions, with the former mimicking the low pH environment within endosomes, and the latter the high pH conditions accessible to nascent exhaled aerosols. D-NEMD reveals that pH changes trigger distinct, variant-specific conformational responses in key regions of the spike, including the receptor binding domain (RBD), fusion peptide proximal region (FPPR), and C-terminal domain (CTD). The ancestral spike shows broad pH sensitivity, characterised by directional motions and region-specific structural rearrangements that depend on the pH conditions. The spike of the Delta variant displays increased reactivity to alkaline pH, potentially explaining its reduced stability in alkaline aerosols. The spike of Omicron BA.1, in contrast, responds strongly to acidic conditions with spontaneous RBD opening and pronounced structural rearrangements in the FPPR and CTD. This behaviour aligns with this variants preference for endosomal entry and reduced reliance on TMPRSS2-mediated fusion. The Omicron BA.1 spike also shows increased resilience to alkaline pH, suggesting greater environmental stability. Our findings further emphasise the key role of glycans in spike activation, with glycan N234 stabilising the RBD "up" conformation during pH-induced transitions in Omicron under acidic conditions. These insights, together, highlight pH as a potential evolutionary pressure for SARS-CoV-2 and underscore the importance of glycosylation and environmental pH variability in shaping the behaviour of viral fusion proteins.

biochemistry↗