Dataset Information

Targeting of disease-linked mutations in PI3K gamma

ABSTRACT: Using hydrogen deuterium exchange mass spectrometry (HDX-MS) and molecular dynamics we have identified mutation specific conformational changes, and provide a molecular framework for how they alter kinase activity.Many of the activating conformational changes mimicked previously described changes that occur upon membrane binding and allosteric inhibitor binding. We surveyed a diverse panel of PI3K inhibitors using HDX-MS and X-ray crystallography, and find that inhibitors that interact with the activation loop lead to allosteric conformational changes that partially mimic the R1021C mutation. Intriguingly, inhibitors that showed similar conformational changes to the activating mutant showed increased potency (~3 fold) for the mutant over wild type PI3K. Overall this work provides unique insight into the regulatory mechanisms that control PI3K kinase activity, and reveals a framework for the potential design of PI3K isoform and mutant selective inhibitors.

INSTRUMENT(S): impact HD

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: John Burke

LAB HEAD: Dr. John E Burke

PROVIDER: PXD021132 | Pride | 2021-03-26

REPOSITORIES: Pride

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Publications

Disease-related mutations in PI3Kγ disrupt regulatory C-terminal dynamics and reveal a path to selective inhibitors.

Rathinaswamy Manoj K MK Gaieb Zied Z Fleming Kaelin D KD Borsari Chiara C Harris Noah J NJ Moeller Brandon E BE Wymann Matthias P MP Amaro Rommie E RE Burke John E JE

eLife 20210304

Class I Phosphoinositide 3-kinases (PI3Ks) are master regulators of cellular functions, with the class IB PI3K catalytic subunit (p110γ) playing key roles in immune signalling. p110γ is a key factor in inflammatory diseases and has been identified as a therapeutic target for cancers due to its immunomodulatory role. Using a combined biochemical/biophysical approach, we have revealed insight into regulation of kinase activity, specifically defining how immunodeficiency and oncogenic mutations of ...[more]

PMID: 33661099

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Project description:Multiple respiratory viruses including Influenza A virus (IAV) can be transmitted via expiratory aerosol particles, and many studies have established that environmental conditions can affect viral infectivity during airborne transmission. Low aerosol pH was recently identified as a major factor influencing the infectivity of aerosol-borne IAV and SARS-CoV-2, however, there is a fundamental lack of understanding as to the mechanisms leading to viral inactivation within the acidic aerosol micro-environment. Here, we identified that the early stages of the IAV infection cycle were impacted by transient exposure to acidic aerosol conditions (pH below 5.5), which was primarily attributed to loss of binding function of the viral protein haemagglutinin. Viral capsid integrity was also somewhat affected by transient acidic exposure. We then characterised the structural changes associated with loss of viral infectivity using whole-virus hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS), and observed discrete regions of unfolding in the external viral protein haemagglutinin and in the internal matrix protein 1. Viral nucleoprotein structure appeared to be unaffected by exposure to acidic aerosol conditions, and no changes to viral genome integrity or to lipids within the viral envelope were detected using our whole-virus methods. Collectively, these data indicate that viral inactivation observed under indoor aerosol conditions is mediated by specific protein conformational changes, particularly to haemagglutinin. This study additionally provides a proof-of-concept that HDX-MS is a highly effective method for characterisation of internal and external proteins of whole enveloped viruses such as IAV. Overall, improved understanding of the fate of respiratory viruses within exhaled aerosols will aid the development of novel strategies and therapeutics to control the severity of seasonal and/or pandemic influenza, and constitutes a global public health priority.

Project description:To directly observe the conformational changes in Akt1 3P elicited by PIP 3 binding, we performed HDX-MS analysis of Akt1 3P in the presence of plasma membrane-mimicking liposomes (20% cholesterol, 30% phosphatidylcholine, 15% phosphatidylserine, 35% phosphatidylethanolamine) that contained either 0% or 5% PIP 3 . The sequence coverage of Akt1 was excellent, with 160 peptides spanning ~97% of all exchangeable amides (Supplementary Table 2). With 5% PIP 3 liposomes there was extensive protection of the PH domain, similar to what had been previously observed for non-phosphorylated Akt1. In addition to protection of the PH domain elicited by PIP 3 binding, Akt1 3P exhibited significant deprotection of the C-lobe of the kinase domain, including the activation loop, that corresponds to the interface between the PH and kinase domains observed in our structure of autoinhibited Akt1. We also carriedout HDX-MS experiments in the presence and absence of ATPS, for which we observed no significant differences. The likely binding pocket for the hydrophobic motif is the so-called PDK1- interacting fragment (PIF) pocket in Akt that binds the phosphorylated hydrophobic motif in the active conformation (21, 22) . Previous hydrogen- deuterium exchange mass spectrometry (HDX-MS) analysis of Akt1 DrLink indicated small, but significant exposure of the PIF pocket upon PI(3,4,5)P 3 binding (26) (Figure 5D, deuterium incorporation plots reproduced with permission). We confirmed this observation by comparing the deuterium incorporation rates for Akt1 DrLink and Akt1 ΔC in solution. Sequence coverage of the truncated Akt1 ΔC comprised 85 peptides spanning ~94% of all exchangeable amides (Supplementary Table 2). Two peptides in Akt1 ΔC , corresponding to β3-αB in the N-lobe and the catalytic loop in the C-lobe of the kinase domain exhibited a modest, but significant, 6% increase in deuterium incorporation (Figure 5E). These changes indicate exposure of the PIF pocket and consequent local disordering of the N-lobe in the absence of the hydrophobic motif. These observationsis areis consistent with the lack of electron density observed for theC helix and activation loop and overall higher temperature factors for the N- lobe of the kinase domain (Supplementary Figure S5CD). In order to test whether the unphosphorylated hydrophobic motif indeed binds to the PIF pocket in the inactive conformation, we measured the binding affinity of a tail peptide 19 containing the missing C-terminal tail residues in Akt1 ΔC (residues 457-480 of human Akt1) by fluorescence anisotropy. The binding constant was estimated to be approximately 0.5 mM from three independent titrations (Figure 5F), although it was not possible to reach saturation due to limiting Akt1 ΔC concentration. Whilst this is a relatively weak interaction, it is sufficient in the context of an intramolecular interaction to sequester the hydrophobic motif more than 99% of the time at equilibrium due to the almost infinite local concentration.

Dataset Information

Targeting of disease-linked mutations in PI3K gamma

Publications

Disease-related mutations in PI3Kγ disrupt regulatory C-terminal dynamics and reveal a path to selective inhibitors.

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