Dataset Information

Mapping and quantification of phosphorylation sites on protein kinase Akt by LC-MS/MS

ABSTRACT: Mass spectrometry analysis of various Akt species was a cornerstone for elucidating the mechanism of its activation/autoinhibition. By combining intact mass measurements with LC-MS/MS we were able to characterize Akt species comprehensively and relate their biological activity to specific phosphorylation patterns.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Dorothea Anrather

LAB HEAD: Thomas A. Leonard

PROVIDER: PXD022044 | Pride | 2021-08-13

REPOSITORIES: Pride

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Dataset's files

Source:

			Action	DRS
	20190506_QExHFX2_RSLC4_Leonard_Leonard_MFPL_insol_Akt1_EPL169_3P_pepsin.raw	Raw
	20190506_QExHFX2_RSLC4_Leonard_Leonard_MFPL_insol_Akt1_EPL169_3P_trypsin.raw	Raw
	20190506_QExHFX2_RSLC4_Leonard_Leonard_MFPL_insol_Akt1_SR_pepsin.raw	Raw
	20190506_QExHFX2_RSLC4_Leonard_Leonard_MFPL_insol_Akt1_SR_trypsin.raw	Raw
	20200718_QExHFX1_RSLC1_Truebestein_Leonard_MFPL_3A1.raw	Raw

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Publications

Structure of autoinhibited Akt1 reveals mechanism of PIP3-mediated activation.

Truebestein Linda L Hornegger Harald H Anrather Dorothea D Hartl Markus M Fleming Kaelin D KD Stariha Jordan T B JTB Pardon Els E Steyaert Jan J Burke John E JE Leonard Thomas A TA

Proceedings of the National Academy of Sciences of the United States of America 20210801 33

The protein kinase Akt is one of the primary effectors of growth factor signaling in the cell. Akt responds specifically to the lipid second messengers phosphatidylinositol-3,4,5-trisphosphate [PI(3,4,5)P3] and phosphatidylinositol-3,4-bisphosphate [PI(3,4)P2] via its PH domain, leading to phosphorylation of its activation loop and the hydrophobic motif of its kinase domain, which are critical for activity. We have now determined the crystal structure of Akt1, revealing an ...[more]

PMID: 34385319

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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.

Project description:Gliadin triggers T-cell mediated immunity in celiac disease, and has cytotoxic effects on enterocytes mediated through obscure mechanisms. In addition, gliadin transport mechanisms, potential cell surface receptors and gliadin-activated downstream signaling pathways are not completely understood. In order to screen for novel downstream gliadin target genes we performed a systematic whole genome expression study on intestinal epithelial cells. Undifferentiated Caco-2 cells were exposed to pepsin- and trypsin- digested gliadin (PT-G), a blank pepsin-trypsin control (PT) and to a synthetic peptide corresponding to gliadin p31-43 peptide for six hours. RNA from four different experiments was used for hybridization on Agilent one color human whole genome DNA microarray chips. The microarray data were analyzed using the Bioconductor package LIMMA. Genes with nominal p < 0.01 were considered statistically significant. Compared to the untreated cells 1705, 1755 and 211 probes were affected by PT-G, PT and p31-43 respectively. 46 probes were significantly different between PT and PT-G treated cells. Among the p31-43 peptide affected probes, 10 and 21 probes were affected by PT-G and PT respectively. Only PT-G affected genes could be validated by quantitative real-time polymerase chain reaction. All the genes were, nonetheless, also affected to a comparable level by PT treated negative controls. In conclusion, we could not replicate previously reported direct effects of gliadin peptides on enterocytes. The PT-G affected genes in the microarray analysis were validated by qRT-PCR, however these genes were also affected by PT treated negative controls suggesting that certain epitopes derived from pepsin and trypsin may also affect epithelial cell gene transcription. Our study demonstrates novel non-enzymatic effects of pepsin and trypsin on cells and calls for proper controls in pepsin and trypsin digested gliadin experiments. It is conceivable that gliadin effects on enterocytes are secondary mediated through oxidative stress, NFkB activation and IL-15 up-regulation. In total, 16 samples were analyzed of which 4 were control (MED) samples, 4 samples of p31-43 treatment, 4 samples of PT treatmetn and 4 samples of PT-G treatment

Dataset Information

Mapping and quantification of phosphorylation sites on protein kinase Akt by LC-MS/MS

Dataset's files

Publications

Structure of autoinhibited Akt1 reveals mechanism of PIP<sub>3</sub>-mediated activation.

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