Biology subjects

Macartney, T. J.

Publications and source records attributed to Macartney, T. J..

7 recordsLinked to original sources

bioRxiv2026

Targeted dephosphorylation of Tau at the endogenous level promotes its association with microtubules.

Hyperphosphorylation of Tau is a contributory factor for Tauopathies, which constitute a spectrum of neurodegenerative disorders including Alzheimer's disease (AD). Inhibitors of Tau kinases or activators of the Tau phosphatase PP2A to reverse Tau hyperphosphorylation have shown limited therapeutic promise, due primarily to a lack of Tau selectivity. An innovative strategy to potentially circumvent these limitations would be to selectively target the dephosphorylation of phospho-residues on Tau. In this study, we provide evidence for targeted dephosphorylation of phospho-Tau at the endogenous level, including those known to promote Tau aggregation. By recruiting PPP1CA and PPP2CA Affinity-directed (Ad)-Phosphatases to Tau, we demonstrate highly selective targeted dephosphorylation of multiple phospho-residues on Tau in SK-N-MC neuroblastoma cells, leading to its stabilization in microtubules. Moreover, by using a heterobifunctional molecule termed BDPIC (bromoTAG-dTAG proximity-inducing chimera) in cells harbouring bromoTAG and dTAG knockins on Tau and PPP2CA, respectively, we demonstrate highly selective dephosphorylation phospho-residues on Tau.

neuroscience↗

bioRxiv2025

Mutations within the predicted fragment-binding region of FAM83G/SACK1G abolish its interaction with the Ser/Thr kinase CK1α

SACK1G (aka FAM83G, PAWS1) plays a central role in activating canonical WNT signalling via interaction with the Ser/Thr kinase CK1. This loss of CK1 binding and WNT signalling underlies the pathogenesis of Palmoplantar Keratoderma (PPK) caused by several reported mutations in the SACK1G gene. We modelled the scaffold anchor of CK1 (SACK1) domain of SACK1G and used fragment-bound structures of the SACK1B (FAM83B) dimer to guide our analysis. This allowed us to computationally predict several key residues near the fragment-binding site in SACK1G that may be important for its function. We mutated these residues, introduced them into SACK1G-/- DLD-1 colorectal cancer cells and investigated their ability to bind endogenous CK1. We uncovered two SACK1G mutations, namely Y204A and I206A, that abolish interaction with CK1 similarly to the PPK pathogenic mutant A34E. Consistent with this loss of SACK1G-CK1 interaction, the molecular glue degrader of CK1, DEG-77, fails to co-degrade the Y204A and I206A mutants while it still co-degrades native SACK1G. Our findings demonstrate the utility of our computational methods to uncover functional residues on proteins based on fragment-binding sites.

cell biology↗

bioRxiv2025

The contribution of native protein complexes to targeted protein degradation

Targeted protein degradation (TPD) destroys proteins of interest (POIs) by hijacking the cellular proteolytic machinery. Most proteins in cells exist and function as part of multi-protein or macromolecular complexes, thereby allowing a single protein to control multiple biological processes. Therefore, when a small molecule degrader induces proximity between an E3 ligase and the POI, the macromolecular context of the POI potentially influences the degradation outcomes of the POI and of the complex components. Here, we explore degradation of the eight CK1-SACK1(A-H) (formerly known as FAM83A-H) complexes initiated by molecular glue degraders primarily designed to target Ser/Thr kinase CK1. We demonstrate that lenalidomide-derived degraders DEG-77 and SJ3149, which selectively target the CK1 isoform, co-degrade multiple SACK1(A-H) proteins. We show that the degradation of SACK1(A-H) proteins by DEG-77 and SJ3149 requires CK1, the CUL4ACRBN E3 ligase complex and the proteasome. In cells derived from palmoplantar keratoderma patients harbouring the CK1-binding deficient SACK1GR265P mutation, DEG-77 targets CK1 and mitotic SACK1D but not SACK1GR265P, highlighting the requirement for CK1-SACK1(A-H) interaction to achieve co-degradation. Our study underscores the importance of POI context in TPD and reinforces the potential for selectively targeting specific protein complexes for degradation.

cell biology↗

bioRxiv2024

NOTCH1 S2513 is critical for the regulation of NICD levels impacting the segmentation clock in hiPSC-derived PSM cells and somitoids

The segmentation clock is a molecular oscillator that regulates the timing of somite formation in the developing vertebrate embryo. NOTCH signalling is one of the key pathways required for proper functioning of the segmentation clock. Aberrant NOTCH signalling results in developmental abnormalities such as congenital scoliosis as well as diseases such as T-cell acute lymphoblastic lymphoma (T-ALL). In this study we analyse the effects of a mutation detected in T-ALL patients on somitogenesis using human iPS derived PSM cells and somitoids. Mutation of NOTCH1 Serine 2513 into Alanine compromises the interaction of Notch intracellular domain (NICD) with the F-box protein FBXW7 and consequently increases NICD stability and NICD levels in PSM cells. Moreover, the mutation impairs several aspects of clock gene oscillations and restricts the ability of somitoids to polarise, elongate and form paired somites. The data suggest a mechanism by which post-translational modification of a key segmentation clock component plays a crucial role in vertebrate axis segmentation.

developmental biology↗

bioRxiv2019

Targeting endogenous K-RAS for degradation through the affinity-directed protein missile system

For over three decades, K-RAS has been known as the holy grail of cancer targets, one of the most frequently mutated oncogenes in cancer. Because the development of conventional small molecule K-RAS inhibitors has been extremely challenging, K-RAS has been dubbed as an undruggable target, and only recently a mutation specific inhibitor has reached clinical trials. Targeted protein degradation has emerged as a new modality in drug discovery to tackle undruggable targets. However, no degrader for K-RAS has been described thus far. Our laboratory has developed an Affinity-directed PROtein Missile (AdPROM) system for targeted proteolysis of endogenous proteins through the ubiquitin proteasome system. Here, we show that we can achieve degradation of endogenous K-RAS and H-RAS in different cell lines in a targeted manner using our AdPROM system. Our findings imply that endogenous RAS proteins can be targeted for proteolysis, thereby offering tantalising possibilities for an alternative therapeutic approach to these so-called undruggable targets in cancer.

molecular biology↗

bioRxiv2019

A conserved ATG2-GABARAP interaction is critical for phagophore closure

The intracellular trafficking pathway, macroautophagy, acts as a recycling and disposal service that can be upregulated during periods of stress, to maintain cellular homeostasis. An essential transition point in the pathway is the sealing of the immature phagophore to form an autophagosome, isolating unwanted cargo prior to lysosomal degradation. However, little mechanistic detail is known about phagophore closure. Human ATG2A and ATG2B proteins, through their interaction with WIPI proteins, are thought to be key players during phagophore closure. We have identified a highly-conserved motif driving the interaction between human ATG2 and GABARAP proteins that is in close proximity to the ATG2-WIPI4 interaction site. We show that the ATG2-GABARAP interaction mutants are unable to close phagophores resulting in blocked autophagy, similar to ATG2A/ATG2B double knock-out cells. In contrast, the ATG2-WIPI4 interaction mutant fully restored phagophore closure and autophagy flux, similar to wild type ATG2. Taken together, we provide new mechanistic insights to the requirements for ATG2 function at the phagophore and suggest that an ATG2-GABARAP interaction is essential for phagophore closure, whereas ATG2-WIPI4 interaction is dispensable.

cell biology↗

bioRxiv2017

FAM83G/PAWS1 controls cytoskeletal dynamics and cell migration through association with the SH3 adaptor CD2AP

Our previous studies of PAWS1 (Protein Associated With SMAD1) have suggested that this molecule has roles beyond BMP signalling. To investigate these roles, we have used CRISPR/Cas9 to generate PAWS1 knockout cells. Here, we show that PAWS1 plays a role in the regulation of the cytoskeletal machinery, including actin and focal adhesion dynamics, and cell migration. Confocal microscopy and live cell imaging of actin in U2OS cells indicate that PAWS1 is also involved in cytoskeletal dynamics and organization. Loss of PAWS1 causes severe defects in F-actin organization and distribution as well as in lamellipodial organization, resulting in impaired cell migration. PAWS1 interacts in a dynamic fashion with the actin/cytoskeletal regulator CD2AP at lamellae, suggesting that its association with CD2AP controls actin organization and cellular migration.\n\nSummary statementPAWS1/FAM83G controls cell migration by influencing the organisation of F-actin and focal adhesions and the distribution of the actin stress fibre network through its association with CD2AP.

cell biology↗