Dataset Information

Molecular basis for differential activation of p101 and p84 complexes of PI3Kg by Ras and GPCRs

ABSTRACT: Using hydrogen deuterium exchange mass spectrometry, we reveal molecular differences between the two p110g-p84 and p110g-p101 complexes that explain their differential activation.

INSTRUMENT(S): impact HD

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: John Burke

LAB HEAD: John Burke

PROVIDER: PXD035723 | Pride | 2023-03-09

REPOSITORIES: Pride

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Dataset's files

Source:

			Action	DRS
	05_20_22_HPHDX17_p101_MSMS_0_01_19395.d.rar	Other
	05_20_22_HPHDX17_p101_ND_H_0_01_19397.d.rar	Other
	05_24_22_HPHDX17_A_300s_1_0_01_19408.d.rar	Other
	05_24_22_HPHDX17_B_300s_1_0_01_19410.d.rar	Other
	05_24_22_HPHDX17_p84_MSMS_0_01_19404.d.rar	Other

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Molecular basis for differential activation of p101 and p84 complexes of PI3Kγ by Ras and GPCRs.

Rathinaswamy Manoj K MK Jenkins Meredith L ML Duewell Benjamin R BR Zhang Xuxiao X Harris Noah J NJ Evans John T JT Stariha Jordan T B JTB Dalwadi Udit U Fleming Kaelin D KD Ranga-Prasad Harish H Yip Calvin K CK Williams Roger L RL Hansen Scott D SD Burke John E JE

Cell reports 20230226 3

Class IB phosphoinositide 3-kinase (PI3Kγ) is activated in immune cells and can form two distinct complexes (p110γ-p84 and p110γ-p101), which are differentially activated by G protein-coupled receptors (GPCRs) and Ras. Using a combination of X-ray crystallography, hydrogen deuterium exchange mass spectrometry (HDX-MS), electron microscopy, molecular modeling, single-molecule imaging, and activity assays, we identify molecular differences between p110γ-p84 and p110γ-p101 that explain their differ ...[more]

PMID: 36842083

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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.