Journal: Cell Rep / Year: 2023 Title: Molecular basis for differential activation of p101 and p84 complexes of PI3Kγ by Ras and GPCRs. Authors: Manoj K Rathinaswamy / Meredith L Jenkins / Benjamin R Duewell / Xuxiao Zhang / Noah J Harris / John T Evans / Jordan T B Stariha / Udit Dalwadi / Kaelin D Fleming / Harish Ranga-Prasad / ...Authors: Manoj K Rathinaswamy / Meredith L Jenkins / Benjamin R Duewell / Xuxiao Zhang / Noah J Harris / John T Evans / Jordan T B Stariha / Udit Dalwadi / Kaelin D Fleming / Harish Ranga-Prasad / Calvin K Yip / Roger L Williams / Scott D Hansen / John E Burke / Abstract: 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 ...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 differential membrane recruitment and activation by Ras and GPCRs. The p110γ-p84 complex is dynamic compared with p110γ-p101. While p110γ-p101 is robustly recruited by Gβγ subunits, p110γ-p84 is weakly recruited to membranes by Gβγ subunits alone and requires recruitment by Ras to allow for Gβγ activation. We mapped two distinct Gβγ interfaces on p101 and the p110γ helical domain, with differences in the C-terminal domain of p84 and p101 conferring sensitivity of p110γ-p101 to Gβγ activation. Overall, our work provides key insight into the molecular basis for how PI3Kγ complexes are activated.
Supramolecule #1: Ternary complex of p110 gamma with p84
Supramolecule
Name: Ternary complex of p110 gamma with p84 / type: complex / ID: 1 / Parent: 0 / Details: Both p110 and p84 subunits are from Homo sapiens
Source (natural)
Organism: Homo sapiens (human)
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Experimental details
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Structure determination
Method
negative staining
Processing
single particle reconstruction
Aggregation state
particle
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Sample preparation
Concentration
0.02 mg/mL
Buffer
pH: 8.5 Component:
Concentration
Name
Formula
20.0 mM
Tris(hydroxymethyl)aminomethane-Hydrochloric acid
100.0 mM
Sodium Chloride
NaCl
50.0 mM
Ammonium Sulfate
(NH4)2SO4
0.5 mM
Tris(2-carboxyethyl)phosphine
Details: Freshly prepared gel filtration buffer, filtered through 0.22 um filter and degassed
Staining
Type: NEGATIVE / Material: Uranyl Formate Details: Negative stain EM samples prepares by adsorbing samples on grid for 15 second, followed by blotting of sample, 2 washes with water, 1 wash with stain, and a final 30 second soak in stain and blot.
Grid
Model: Homemade / Material: COPPER / Support film - Material: CARBON / Support film - topology: CONTINUOUS
Details
Specimen was a 1:1 molar ratio of p110g to p84, purified to homogeneity by gel filtration.
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Electron microscopy
Microscope
FEI TECNAI SPIRIT
Image recording
Film or detector model: FEI EAGLE (4k x 4k) / Digitization - Dimensions - Width: 4096 pixel / Digitization - Dimensions - Height: 4096 pixel / Number grids imaged: 1 / Number real images: 50 / Average exposure time: 1.0 sec. / Average electron dose: 25.0 e/Å2
Electron beam
Acceleration voltage: 120 kV / Electron source: LAB6
Model: Tecnai Spirit / Image courtesy: FEI Company
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Image processing
Details
CTF estimation and manual particle picking were done using Relion 3.0.8. Manually picked particles were 2D classified into 4 classes and used as templates for autopicking. Autopicked particles were exported to cryoSPARC 2.14.2 and subjected to 2D classification. Particles which classified well were selected and used to generate an ab initio 3D reconstruction.
Particle selection
Number selected: 20610 Details: Particles were picked using the cryoSPARC template picker.
Startup model
Type of model: NONE / Details: Ab initio reconstruction
Final reconstruction
Resolution.type: BY AUTHOR / Resolution: 17.1 Å / Resolution method: FSC 0.143 CUT-OFF / Software - Name: cryoSPARC (ver. 2.14.3) / Number images used: 10344
Initial angle assignment
Type: MAXIMUM LIKELIHOOD / Software - Name: cryoSPARC (ver. 2.14.2) / Details: cryoSPARC SGD-based ab intio reconstruction
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