Biology subjects

Shaw, A. L.

Publications and source records attributed to Shaw, A. L..

5 recordsLinked to original sources

bioRxiv2026

Phosphorylation of the C-terminus of PI4KA inhibits lipid kinase activity

Phosphatidylinositol 4-kinase alpha (PI4KA) is a lipid kinase that generates phosphatidylinositol 4-phosphate (PI4P) from phosphatidylinositol (PI) at the plasma membrane (PM). PI4P generated by PI4KA is essential for both plasma membrane identity and for PIP2 and PIP3 signalling driven by the PLC and PI3K family of enzymes. While the structure of PI4KA is known, the regulatory mechanisms that control its activity are undefined. Here, we discovered PI4KA can be inhibited through phosphorylation of Y2090 in the kinase domain, which can be phosphorylated by multiple tyrosine kinases. Y2090 phosphorylation causes local conformational changes in the k12 C-terminal helix. PI4KA activity is predominantly controlled through membrane recruitment by EFR3, with Y2090 phosphorylation inhibiting EFR3 bound PI4KA. Phosphorylation of the k12 C-terminal helix is found in PI3Ks and PI4Ks, suggesting an evolutionarily conserved regulatory mechanism for diverse phosphoinositide kinases. Overall, our work reveals novel molecular insight into inhibitory post-translational regulation of PI4KA.

biochemistry↗

bioRxiv2025

Development of an inhibitory TTC7B selective nanobody that blocks EFR3 recruitment of PI4KA

Phosphatidylinositol 4 kinase III (PI4KIII/PI4KA) is an essential lipid kinase that plays a critical role in regulating plasma membrane identity. PI4KA is primarily recruited to the plasma membrane through the targeted recruitment by the proteins, EFR3A and EFR3B, which bind to the PI4KA accessory proteins TTC7 (TTC7A/B) and FAM126 (FAM126A/B). Here we characterised how both EFR3 isoforms interact with all possible TTC7-FAM126 combinations and developed a nanobody that specifically blocked EFR3-mediated PI4KA recruitment in TTC7B containing complexes. Most EFR3-TTC7-FAM126 combinations show similar binding affinities, with the exception of EFR3A-TTC7B-FAM126A, which binds with a [~]10-fold higher affinity. Moreover, we showed that EFR3B phosphorylation markedly decreased binding to TTC7-FAM126. Using a yeast display approach, we isolated a TTC7B selective nanobody that blocked EFR3 binding. Cryo-electron microscopy and hydrogen deuterium exchange mass spectrometry showed an extended interface with both PI4KA and TTC7B that sterically blocks EFR3 binding. The nanobody caused decreased membrane recruitment both on lipid bilayers and in cells, with decreased PM production of PI4P. Collectively, these findings provide new insights into PI4KA regulation and provide a tool for manipulating PI4KA complexes, that may be valuable for therapeutic targeting.

biochemistry↗

bioRxiv2024

Molecular basis for plasma membrane recruitment of PI4KA by EFR3

The lipid kinase phosphatidylinositol 4 kinase III alpha (PI4KIII/PI4KA) is a master regulator of the lipid composition and asymmetry of the plasma membrane. PI4KA exists primarily in a heterotrimeric complex with its regulatory proteins TTC7 and FAM126. Fundamental to PI4KA activity is its targeted recruitment to the plasma membrane by the lipidated proteins EFR3A and EFR3B. Here, we report a cryo-EM structure of the C-terminus of EFR3A bound to the PI4KA-TTC7B-FAM126A complex, with extensive validation using both hydrogen deuterium exchange mass spectrometry (HDX-MS), and mutational analysis. The EFR3A C-terminus undergoes a disorder-order transition upon binding to the PI4KA complex, with an unexpected direct interaction with both TTC7B and FAM126A. Complex disrupting mutations in TTC7B, FAM126A, and EFR3 decrease PI4KA recruitment to the plasma membrane. Multiple post-translational modifications and disease linked mutations map to this site, providing insight into how PI4KA membrane recruitment can be regulated and disrupted in human disease. One sentence summaryThe cryo-EM structure of the C-terminus of EFR3A bound to the PI4KA complex reveals the molecular mechanism underlying PI4KA membrane localisation, and provides novel insight into PI4KA regulation and its involvement in human disease.

biochemistry↗

bioRxiv2024

Structure of Calcineurin bound to PI4KA reveals dual interface in both PI4KA and FAM126A

Phosphatidylinositol 4-kinase alpha (PI4KA) maintains the PI4P and phosphatidylserine pools of the plasma membrane. A key regulator of PI4KA is its association into a complex with TTC7 and FAM126 proteins. This complex can be regulated by the CNA{beta}1 isoform of the phosphatase Calcineurin. We previously identified that CNA{beta}1 directly binds to FAM126A. Here, we report a cryo-EM structure of a truncated PI4KA complex bound to Calcineurin, revealing a direct Calcineurin interaction with PI4KA. Additional HDX-MS and computational analysis show that Calcineurin forms a complex with an evolutionarily conserved IKISVT sequence in PI4KAs horn domain. We also characterised conserved LTLT and PSISIT Calcineurin binding sequences in the C-terminus of FAM126A. These sites are in close proximity to phosphorylation sites in the PI4KA complex, suggesting key roles of Calcineurin-regulated phosphosites in PI4KA regulation. This work reveals novel insight into how Calcineurin can regulate PI4KA activity.

biochemistry↗

bioRxiv2022

ATP-competitive and allosteric inhibitors induce differential conformational changes at the auto-inhibitory interface of Akt

The protein kinase Akt is a master regulator of pro-growth signalling in the cell. Akt is activated through its targeted recruitment to phosphoinositides, leading to disruption of the autoinhibitory interface between the kinase and pleckstrin homology (PH) domains. Hyper activation of Akt is common in oncogenic transformation, with multiple oncogenic activating mutants identified in Akt. This has led to the development of potent and selective ATP-competitive and allosteric inhibitors for Akt. Paradoxically, some ATP-competitive Akt inhibitors cause hyperphosphorylation of Akt. Here, using hydrogen deuterium exchange mass spectrometry (HDX-MS), we interrogated the conformational changes upon binding to the Akt active site inhibitor A-443654, and the Akt allosteric inhibitor MK-2206. We compared the conformational changes that occurred for each inhibitor under three different states of Akt: i-inactive monophosphorylated, ii-partially active tris-phosphorylated [T308, T450, S473], and iii-fully activated, tris-phosphorylated bound to PIP3 membranes. The allosteric MK-2206 inhibitor results in large scale allosteric conformational changes in all states, and restricts membrane binding through sequestration of the PH domain. Binding of the A-443654 inhibitor led to large scale allosteric conformational changes in both the monophosphorylated and phosphorylated states, leading to an alteration in the autoinhibitory PH-kinase interface. We also observed increased protection in the PH domain upon membrane binding in the presence of A-443654, suggesting that the PH domain is more accessible for membrane binding. This work provides unique insight into the autoinhibitory conformation of the PH and kinase domain and dynamic conformational changes induced by Akt inhibitors, and has important implications for the design of Akt targeted therapeutics.

biochemistry↗