👤 Nicole T Watt

Lipoprotein(a) [Lp(a)] is a well recognised contributor in the development of cardiovascular disease. Unlike other lipoproteins, Lp(a) levels are primarily genetically determined, and in most individuals remain largely stable throughout life. Elevated Lp(a) is common in the general population, and various international guidelines now recommend at least one lifetime measurement of Lp(a) and its inclusion into an individual's cardiovascular risk assessment. Despite this, Lp(a) is still rarely measured, even in patients with known cardiovascular risk factors. Critically, the therapeutic landscape for Lp(a)-lowering medications is rapidly evolving with multiple drugs showing considerable promise in late-stage clinical trials. The strength and consistency of the evidence now cement Lp(a) as an essential biomarker of cardiovascular health. Failure to incorporate measurement of Lp(a) into clinical practice will continue to underestimate an individual's risk of CVD. Now is the time for Lp(a) to move from a neglected biomarker to a widely known and measured essential component of cardiovascular risk assessment. Show less

The β-site Amyloid precursor protein Cleaving Enzyme 1 (BACE1) is an extensively studied therapeutic target for Alzheimer's disease (AD), owing to its role in the production of neurotoxic amyloid beta (Aβ) peptides. However, despite numerous BACE1 inhibitors entering clinical trials, none have successfully improved AD pathogenesis, despite effectively lowering Aβ concentrations. This can, in part, be attributed to an incomplete understanding of BACE1, including its physiological functions and substrate specificity. We propose that BACE1 has additional important physiological functions, mediated through substrates still to be identified. Thus, to address this, we computationally analysed a list of 533 BACE1 dependent proteins, identified from the literature, for potential BACE1 substrates, and compared them against proteins differentially expressed in AD. We identified 15 novel BACE1 substrates that were specifically altered in AD. To confirm our analysis, we validated Protein tyrosine phosphatase receptor type D (PTPRD) and Netrin receptor DCC (DCC) using Western blotting. These findings shed light on the BACE1 inhibitor failings and could enable the design of substrate-specific inhibitors to target alternative BACE1 substrates. Furthermore, it gives us a greater understanding of the roles of BACE1 and its dysfunction in AD. Show less

Glucose-dependent insulinotropic polypeptide (GIP) is best known as an incretin hormone that is secreted from K-cells of the proximal intestine, but evidence also implicates a role for GIP in regulating lipid metabolism and adiposity. It is well-established that GIP receptor knockout (GIPR KO) mice are resistant to diet-induced obesity; however, the factors mediating this effect remain unresolved. Accordingly, we aimed to elucidate the mechanisms leading to adiposity resistance in GIPR KO mice with a focus on whole-body energy balance and lipid metabolism in adipose tissues. Studies were conducted in age-matched male GIPR KO and wild-type (WT) mice fed a high-fat diet for 10 weeks. GIPR KO mice gained less body weight and fat mass compared to WT littermates, and this was associated with increased energy expenditure but no differences in food intake or fecal energy loss. Upon an oral lipid challenge, fatty acid storage in inguinal adipose tissue was significantly increased in GIPR KO compared with WT mice. This was not related to differential expression of lipoprotein lipase in adipose tissue. Adipose tissue lipolysis was increased in GIPR KO compared with WT mice, particularly following β-adrenergic stimulation, and could explain why GIPR KO mice gain less adipose tissue despite increased rates of fatty acid storage in inguinal adipose tissue. Taken together, these results suggest that the GIPR is required for normal maintenance of body weight and adipose tissue mass by regulating energy expenditure and lipolysis. Show less

Fluctuation in signal transduction pathways is frequently observed during mammalian development. However, its role in regulating stem cells has not been explored. Here we tracked spatiotemporal ERK MAPK dynamics in human epidermal stem cells. While stem cells and differentiated cells were distinguished by high and low stable basal ERK activity, respectively, we also found cells with pulsatile ERK activity. Transitions from Basal Show less

WWP2 is an E3 ubiquitin ligase that differentially regulates the contextual tumour suppressor/progressor TGFβ signalling pathway by alternate isoform expression. WWP2 isoforms select signal transducer Smad2/3 or inhibitor Smad7 substrates for degradation through different compositions of protein-protein interaction WW domains. The WW4 domain-containing WWP2-C induces Smad7 turnover in vivo and positively regulates the metastatic epithelial-mesenchymal transition programme. This activity and the overexpression of these isoforms in human cancers make them candidates for therapeutic intervention. Here, we use NMR spectroscopy to solve the solution structure of the WWP2 WW4 domain and observe the binding characteristics of Smad7 substrate peptide. We also reveal that WW4 has an enhanced affinity for a Smad7 peptide phosphorylated at serine 206 adjacent to the PPxY motif. Using the same approach, we show that the WW3 domain also binds Smad7 and has significantly enhanced Smad7 binding affinity when expressed in tandem with the WW4 domain. Furthermore, and relevant to these biophysical findings, we present evidence for a novel WWP2 isoform (WWP2C-ΔHECT) comprising WW3-WW4 tandem domains and a truncated HECT domain that can inhibit TGFβ signalling pathway activity, providing a further layer of complexity and feedback to the WWP2 regulatory apparatus. Collectively, our data reveal a structural platform for Smad substrate selection by WWP2 isoform WW domains that may be significant in the context of WWP2 isoform switching linked to tumorigenesis. Show less

We have screened small molecule libraries specifically for inhibitors that target WWP2, an E3 ubiquitin ligase associated with tumour outgrowth and spread. Selected hits demonstrated dose-dependent WWP2 inhibition, low micromolar IC50 values, and inhibition of PTEN substrate-specific ubiquitination. Binding to WWP2 was confirmed by ligand-based NMR spectroscopy. Furthermore, we used a combination of STD NMR, the recently developed DEEP-STD NMR approach, and docking calculations, to propose for the first time an NMR-validated 3D molecular model of a WWP2-inhibitor complex. These first generation WWP2 inhibitors provide a molecular framework for informing organic synthetic approaches to improve activity and selectivity. Show less

Epidermal homeostasis depends on a balance between stem cell renewal and terminal differentiation. The transition between the two cell states, termed commitment, is poorly understood. Here, we characterise commitment by integrating transcriptomic and proteomic data from disaggregated primary human keratinocytes held in suspension to induce differentiation. Cell detachment induces several protein phosphatases, five of which - DUSP6, PPTC7, PTPN1, PTPN13 and PPP3CA - promote differentiation by negatively regulating ERK MAPK and positively regulating AP1 transcription factors. Conversely, DUSP10 expression antagonises commitment. The phosphatases form a dynamic network of transient positive and negative interactions that change over time, with DUSP6 predominating at commitment. Boolean network modelling identifies a mandatory switch between two stable states (stem and differentiated) via an unstable (committed) state. Phosphatase expression is also spatially regulated in vivo and in vitro. We conclude that an auto-regulatory phosphatase network maintains epidermal homeostasis by controlling the onset and duration of commitment. Show less

HDL cholesterol levels are decreased in Crohn's disease, a tumor necrosis factor-alpha (TNF-alpha)-driven chronic inflammatory condition involving the gastrointestinal tract. ATP-binding cassette transporter A1 (ABCA1), one of several liver X receptor (LXR) target genes, is a cell surface transporter that mediates the rate-controlling step in HDL synthesis. The regulation of ABCA1 and HDL cholesterol efflux by TNF-alpha was investigated in the human intestinal cell line Caco-2. In response to cholesterol micelles or T0901317, an LXR nonsterol agonist, TNF-alpha decreased the basolateral efflux of cholesterol to apolipoprotein A1 (apoA1). TNF-alpha, by attenuating ABCA1 promoter activity, markedly decreased ABCA1 gene expression without attenuating the expression of LXR-alpha, LXR-beta, and most other LXR target genes, such as ABCG1, FAS, ABCG8, scavenger receptor-B1 (SR-B1), and apoC1. TNF-alpha also decreased ABCA1 mass by markedly enhancing the rate of ABCA1 degradation and modestly inhibiting its rate of synthesis. Inhibitors of the nuclear factor-kappaB (NF-kappaB) pathway, which is activated by TNF-alpha, partially reverse the effect of TNF-alpha on ABCA1 protein expression. The results suggest that TNF-alpha, the major cytokine implicated in the inflammation of Crohn's disease, decreases HDL cholesterol levels by attenuating the expression of intestinal ABCA1 and cholesterol efflux to apoA1. Show less

The Notch pathway is required for hair follicle maintenance and is activated through beta-catenin induced transcription of the Notch ligand Jagged1. We show that hair follicles in the resting phase express low levels of Jagged1 and Hes1, and other Notch target genes are undetectable. In growing (anagen) follicles, Jagged1 and Hes1 expression increases, Hes5 and HeyL are expressed in distinct cell layers, and Hey2 is expressed in the dermal papilla. When beta-catenin is activated by means of an inducible transgene, Jagged1, Hes1, Hes5, HeyL, and Hey2 are up-regulated, the sites of expression being the same in beta-catenin induced ectopic follicles as in anagen follicles. beta-Catenin also induces Hey1 in dermal papilla cells. beta-Catenin-induced up-regulation of Jagged1 precedes induction of other Notch target genes. The different sites of expression of Hes and Hey genes suggest input from additional signaling pathways. Show less