Dataset Information

Structure of the phosphoinositide 3-kinase p110-p101 complex reveals molecular mechanism of GPCR activation

ABSTRACT: The class IB phosphoinositide 3-kinase (PI3K), PI3K, is a master regulator of immune cell function, and is a promising drug target for both inflammatory diseases and cancer. Critical to PI3K function is the association of the p110 catalytic subunit to either a p101 or p84 regulatory subunit, which mediates regulation by G-protein coupled receptors (GPCRs). Here, we report the first structure of a heterodimeric PI3K complex, p110-p101. This structure revealed a unique mode of assembly of catalytic and regulatory subunits distinct from that of other class I PI3K complexes. Multiple oncogenic mutations mapped to these novel interfaces led to increased activation by G. p101 mediates activation through its G binding domain, recruiting the complex to the membrane and allowing for engagement of a secondary site in p110. A nanobody that specifically binds to this p101-G interface blocks activation providing a novel tool to study p101-specific signaling events in vivo.

INSTRUMENT(S): impact HD

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: John Burke

LAB HEAD: Dr. John E Burke

PROVIDER: PXD025209 | Pride | 2021-09-22

REPOSITORIES: Pride

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Publications

Structure of the phosphoinositide 3-kinase (PI3K) p110γ-p101 complex reveals molecular mechanism of GPCR activation.

Rathinaswamy Manoj K MK Dalwadi Udit U Fleming Kaelin D KD Adams Carson C Stariha Jordan T B JTB Pardon Els E Baek Minkyung M Vadas Oscar O DiMaio Frank F Steyaert Jan J Hansen Scott D SD Yip Calvin K CK Burke John E JE

Science advances 20210827 35

The class IB phosphoinositide 3-kinase (PI3K), PI3Kγ, is a master regulator of immune cell function and a promising drug target for both cancer and inflammatory diseases. Critical to PI3Kγ function is the association of the p110γ catalytic subunit to either a p101 or p84 regulatory subunit, which mediates activation by G protein-coupled receptors. Here, we report the cryo-electron microscopy structure of a heterodimeric PI3Kγ complex, p110γ-p101. This structure reveals a unique assembly of catal ...[more]

PMID: 34452907

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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

Structure of the phosphoinositide 3-kinase p110-p101 complex reveals molecular mechanism of GPCR activation

Publications

Structure of the phosphoinositide 3-kinase (PI3K) p110γ-p101 complex reveals molecular mechanism of GPCR activation.

Similar Datasets

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