Biology subjects

Fennell, K.

Publications and source records attributed to Fennell, K..

4 recordsLinked to original sources

bioRxiv2026

Insight into the scaffolding function of USP18 from a high resolution cryo-EM structure of STAT2-USP18-ISG15 ternary complex

USP18 is a primary negative regulator of the type I interferon (IFN-I) signaling which regulates hundreds of IFN-stimulated genes for viral protection and anti-cancer immunity. USP18 plays dual roles in the IFN-I signaling: 1) deubiquitinase enzymatic function which cleaves ISG15 from its substrates and 2) scaffolding function through forming a complex with STAT2 to suppress IFN-I signaling. Targeting the scaffolding function of USP18, instead of its enzyme activity, is crucial for reducing cancer cell fitness and boosting anti-tumor immunity. However, the molecular basis of USP18s scaffolding function remains unclear due to the lack of structural information. Here, using a fusion tag strategy, we captured the transient USP18-STAT2 complex and determined a ternary complex structure of STAT2-USP18-ISG15 at 3.05 [A] resolution by cryogenic electron microscopy (cryo-EM) that delineated detailed USP18-STAT2 interactions. Remarkably, the ternary complex impairs USP18s enzymatic function by STAT2-mediated disruption of its catalytic triad. Structural analysis and mutagenesis identify specific USP18 point mutations, facilitating further investigation into the role of USP18 in IFN-I signaling. Taken together, our findings suggest that USP18s scaffolding function could present an untapped opportunity for cancer therapy.

molecular biology↗

bioRxiv2024

Clonal analysis of fetal hematopoietic stem/progenitor cell subsets reveals how post-transplantation capabilities are distributed

It has been proposed that adult haematopoiesis is sustained by multipotent progenitor (MPP) clones that are specified during development. From an immunophenotypic perspective, it is known that hematopoietic stem cell (HSC) and MPPs are present in the fetal liver yet our understanding of how fetal MPPs functionally compare to those in the adult bone marrow is incomplete. Using acute-term transplantations, we found that at a population-level fetal immunophenotypic MPP classes exhibited similar lineage biases as adult cells, albeit with some difference in lymphoid output. Clonal assessment of fetal MPPs engraftment revealed that lineage biases largely resulted from differences in the pattern of single-or bi-lineage differentiation. Immunophenotypic long-term (LT)-and short-term (ST)-HSCs in the fetal liver were distinguished from MPPs according to propensity for clonal multi-lineage differentiation. We also discovered that a large cohort of long-term repopulating units (LT-RU) were within the immunophenotypic ST-HSC population, a significant portion of these were labelled using Flt3-cre. This finding has two implications: (1) use of the CD150+ LT-HSC immunophenotype alone will systematically underestimate the size and diversity of the fetal LT-RU pool; and, (2), given fetal LT-RUs with a ST-HSC immunophenotype have the functional attributes required to persist into adulthood.

developmental biology↗

bioRxiv2023

Structural reconstruction of individual filaments in Abeta42 fibril populations assembled in vitro reveal rare species that resemble ex vivo amyloid polymorphs from human brains

Structural polymorphism has been demonstrated for both in vitro and ex vivo amyloid fibrils associated with disease. The manner in which different filament structures are assembled from common building blocks remains unclear but the assembly environment is likely to be a key determinant. To address this, three-dimensional reconstruction of individual filament structures was conducted from atomic force microscopy images to map the structural polymorphism landscape of A{beta}42 amyloid fibril populations formed in vitro under most frequently used buffer conditions. The data show sensitivity of A{beta}42 fibril polymorphism to the assembly environment in both the magnitude of heterogeneity and the types of filament species formed. However, some conserved fibril polymorphs were observed across the experimental conditions. Excitingly, by matching individual filament structures to cryo-electron microscopy derived structural data, rare species in these heterogeneous population clouds that show remarkable similarity to A{beta}42 amyloid polymorphs purified from human patient brains were discovered. These results link in vitro experimental approaches with structures formed in vivo, and highlight the polymorph distribution, and the type and magnitude of structural variations within these heterogeneous molecular distributions as important factors in amyloid biology.

biophysics↗

bioRxiv2020

Synaptic dysfunction caused by truncated tau is associated with hyperpolarization-activated cyclic nucleotide-gated channelopathy

Progressive neurodegeneration in tauopathies is mediated through an elusive mechanism. Here, we show that hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are functionally linked to disease-associated abnormalities in tau. Selective rises in the proportion of HCN-positive neurons are detected both in post-mortem human brain from Alzheimers disease and in the Tau35 mouse model of tauopathy. Tau35 mice develop progressive abnormalities including increased phosphorylated tau, enhanced HCN channel expression and decreased dendritic branching, as well as reduced synapse density that is accompanied by vesicle clustering defects. Notably, altered spine density and increased HCN channel expression in Tau35 neurons correlates with functional abnormalities in network properties, including enhanced hyperpolarization-induced membrane voltage sag and changes in the frequency and kinetics of spontaneous excitatory postsynaptic currents. Our findings are consistent with pathological changes in tauopathies impacting on HCN channels to drive network-wide structural and functional synaptic deficits, providing new targets for therapeutic intervention.

neuroscience↗