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Non-canonical antagonism of PI3K by the kinase Itpkb delays thymocyte β-selection and renders it Notch-dependent.

Westernberg L, Conche C, Huang YH, Rigaud S, Deng Y, Siegemund S, Mukherjee S, Nosaka L, Das J, Sauer K - Elife (2016)

Bottom Line: Here, we show that this Notch-dependence is established through antagonistic signaling by the pre-TCR/Notch effector, phosphoinositide 3-kinase (PI3K), and by inositol-trisphosphate 3-kinase B (Itpkb).This is reversed by inhibition of Akt, mTOR or glucose metabolism.Thus, non-canonical PI3K-antagonism by Itpkb restricts pre-TCR induced metabolic activation to enforce coincidence-detection of pre-TCR expression and Notch-engagement.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, United States.

ABSTRACT
β-selection is the most pivotal event determining αβ T cell fate. Here, surface-expression of a pre-T cell receptor (pre-TCR) induces thymocyte metabolic activation, proliferation, survival and differentiation. Besides the pre-TCR, β-selection also requires co-stimulatory signals from Notch receptors - key cell fate determinants in eukaryotes. Here, we show that this Notch-dependence is established through antagonistic signaling by the pre-TCR/Notch effector, phosphoinositide 3-kinase (PI3K), and by inositol-trisphosphate 3-kinase B (Itpkb). Canonically, PI3K is counteracted by the lipid-phosphatases Pten and Inpp5d/SHIP-1. In contrast, Itpkb dampens pre-TCR induced PI3K/Akt signaling by producing IP4, a soluble antagonist of the Akt-activating PI3K-product PIP3. Itpkb(-/-) thymocytes are pre-TCR hyperresponsive, hyperactivate Akt, downstream mTOR and metabolism, undergo an accelerated β-selection and can develop to CD4(+)CD8(+) cells without Notch. This is reversed by inhibition of Akt, mTOR or glucose metabolism. Thus, non-canonical PI3K-antagonism by Itpkb restricts pre-TCR induced metabolic activation to enforce coincidence-detection of pre-TCR expression and Notch-engagement.

No MeSH data available.


Related in: MedlinePlus

Antagonistic signaling by PI3K and Itpkb controls the kinetics and Notch-dependence of β-selection.(A) We propose a model in which pre-TCR and Notch signaling both activate PI3K to produce PIP3 in DN3/DN3-4 cells. PIP3 then recruits and activates Akt to increase glucose metabolism via the Akt/mTOR pathway. This is required for DN3-to-DP cell differentiation. However, pre-TCR signaling also activates Itpkb to produce IP4, which competes with PIP3 for Akt PH domain binding and limits Akt recruitment, Akt and mTOR activation in pre-TCR expressing DN3/DN3-4 cells. IP4 may have additional effectors, indicated by the question mark. By limiting downstream glucose metabolism, this "IP4 brake" delays the kinetics of β-selection and renders this process dependent on Notch costimulation. (B) Without Itpkb, IP4 no more dampens Akt activation and pre-TCR signaling alone sufficiently activates Akt/mTOR signaling to trigger DP cell development in the absence of Notch engagement. (C) In the presence of Notch-signals, Akt is now hyperactivated and causes an accelerated DN3-to-DP cell differentiation.DOI:http://dx.doi.org/10.7554/eLife.10786.015
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fig11: Antagonistic signaling by PI3K and Itpkb controls the kinetics and Notch-dependence of β-selection.(A) We propose a model in which pre-TCR and Notch signaling both activate PI3K to produce PIP3 in DN3/DN3-4 cells. PIP3 then recruits and activates Akt to increase glucose metabolism via the Akt/mTOR pathway. This is required for DN3-to-DP cell differentiation. However, pre-TCR signaling also activates Itpkb to produce IP4, which competes with PIP3 for Akt PH domain binding and limits Akt recruitment, Akt and mTOR activation in pre-TCR expressing DN3/DN3-4 cells. IP4 may have additional effectors, indicated by the question mark. By limiting downstream glucose metabolism, this "IP4 brake" delays the kinetics of β-selection and renders this process dependent on Notch costimulation. (B) Without Itpkb, IP4 no more dampens Akt activation and pre-TCR signaling alone sufficiently activates Akt/mTOR signaling to trigger DP cell development in the absence of Notch engagement. (C) In the presence of Notch-signals, Akt is now hyperactivated and causes an accelerated DN3-to-DP cell differentiation.DOI:http://dx.doi.org/10.7554/eLife.10786.015

Mentions: In thymocytes, TCR engagement activates Itpkb to produce IP4. Itpkb-/- thymocytes had strongly reduced IP3 3-kinase activity and IP4 levels, but normal IP3 levels and Ca2+ mobilization (Huang et al., 2007; Pouillon et al., 2003; Wen et al., 2004). IP4 competitively limits PIP3-binding to the Akt PH domain and Akt activation in NK cells, myeloid cells and HSC (Jia et al., 2008; 2007; Sauer et al., 2013; Siegemund et al., 2015). Thus, we propose that pre-TCR induced IP4/PIP3 antagonism governs β-selection by restricting PI3K/Akt/mTOR signaling and metabolic activation. We derive a model where Itpkb controls pre-TCR/Notch crosstalk through combined restriction of pre-TCR induced and Notch induced PI3K signaling via Akt (Figure 11). Itpkb enforced coincidence detection of pre-TCR surface expression and Notch-engagement ensures that Akt is only activated to the degree needed for β-selection and only in an appropriate context, pre-TCR+ DN3 cells interacting with Notch-ligand expressing subcapsular stromal cells (Petrie and Zuniga-Pflucker, 2007). This prevents premature differentiation. Similarly accelerated DN-to-DP cell development of Itpkb-/- and Pten-/- thymocytes (Hagenbeek et al., 2004; Shiroki et al., 2007) and enhanced DP cell production from DN3 cells expressing a dominant-active mutant version of the class I PI3K regulatory subunit p85α/Pik3r1 (p65PI3K transgenic mice) (Rodriguez-Borlado et al., 2003) or dominant-active, myristoylated Akt1 (myr-Akt transgenic mice) (Lee et al., 2012) highlight the importance of restricting PI3K signaling via Akt for proper β-selection kinetics, even though the specific purpose of delaying DP cell maturation remains unknown.10.7554/eLife.10786.015Figure 11.Antagonistic signaling by PI3K and Itpkb controls the kinetics and Notch-dependence of β-selection.


Non-canonical antagonism of PI3K by the kinase Itpkb delays thymocyte β-selection and renders it Notch-dependent.

Westernberg L, Conche C, Huang YH, Rigaud S, Deng Y, Siegemund S, Mukherjee S, Nosaka L, Das J, Sauer K - Elife (2016)

Antagonistic signaling by PI3K and Itpkb controls the kinetics and Notch-dependence of β-selection.(A) We propose a model in which pre-TCR and Notch signaling both activate PI3K to produce PIP3 in DN3/DN3-4 cells. PIP3 then recruits and activates Akt to increase glucose metabolism via the Akt/mTOR pathway. This is required for DN3-to-DP cell differentiation. However, pre-TCR signaling also activates Itpkb to produce IP4, which competes with PIP3 for Akt PH domain binding and limits Akt recruitment, Akt and mTOR activation in pre-TCR expressing DN3/DN3-4 cells. IP4 may have additional effectors, indicated by the question mark. By limiting downstream glucose metabolism, this "IP4 brake" delays the kinetics of β-selection and renders this process dependent on Notch costimulation. (B) Without Itpkb, IP4 no more dampens Akt activation and pre-TCR signaling alone sufficiently activates Akt/mTOR signaling to trigger DP cell development in the absence of Notch engagement. (C) In the presence of Notch-signals, Akt is now hyperactivated and causes an accelerated DN3-to-DP cell differentiation.DOI:http://dx.doi.org/10.7554/eLife.10786.015
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4764578&req=5

fig11: Antagonistic signaling by PI3K and Itpkb controls the kinetics and Notch-dependence of β-selection.(A) We propose a model in which pre-TCR and Notch signaling both activate PI3K to produce PIP3 in DN3/DN3-4 cells. PIP3 then recruits and activates Akt to increase glucose metabolism via the Akt/mTOR pathway. This is required for DN3-to-DP cell differentiation. However, pre-TCR signaling also activates Itpkb to produce IP4, which competes with PIP3 for Akt PH domain binding and limits Akt recruitment, Akt and mTOR activation in pre-TCR expressing DN3/DN3-4 cells. IP4 may have additional effectors, indicated by the question mark. By limiting downstream glucose metabolism, this "IP4 brake" delays the kinetics of β-selection and renders this process dependent on Notch costimulation. (B) Without Itpkb, IP4 no more dampens Akt activation and pre-TCR signaling alone sufficiently activates Akt/mTOR signaling to trigger DP cell development in the absence of Notch engagement. (C) In the presence of Notch-signals, Akt is now hyperactivated and causes an accelerated DN3-to-DP cell differentiation.DOI:http://dx.doi.org/10.7554/eLife.10786.015
Mentions: In thymocytes, TCR engagement activates Itpkb to produce IP4. Itpkb-/- thymocytes had strongly reduced IP3 3-kinase activity and IP4 levels, but normal IP3 levels and Ca2+ mobilization (Huang et al., 2007; Pouillon et al., 2003; Wen et al., 2004). IP4 competitively limits PIP3-binding to the Akt PH domain and Akt activation in NK cells, myeloid cells and HSC (Jia et al., 2008; 2007; Sauer et al., 2013; Siegemund et al., 2015). Thus, we propose that pre-TCR induced IP4/PIP3 antagonism governs β-selection by restricting PI3K/Akt/mTOR signaling and metabolic activation. We derive a model where Itpkb controls pre-TCR/Notch crosstalk through combined restriction of pre-TCR induced and Notch induced PI3K signaling via Akt (Figure 11). Itpkb enforced coincidence detection of pre-TCR surface expression and Notch-engagement ensures that Akt is only activated to the degree needed for β-selection and only in an appropriate context, pre-TCR+ DN3 cells interacting with Notch-ligand expressing subcapsular stromal cells (Petrie and Zuniga-Pflucker, 2007). This prevents premature differentiation. Similarly accelerated DN-to-DP cell development of Itpkb-/- and Pten-/- thymocytes (Hagenbeek et al., 2004; Shiroki et al., 2007) and enhanced DP cell production from DN3 cells expressing a dominant-active mutant version of the class I PI3K regulatory subunit p85α/Pik3r1 (p65PI3K transgenic mice) (Rodriguez-Borlado et al., 2003) or dominant-active, myristoylated Akt1 (myr-Akt transgenic mice) (Lee et al., 2012) highlight the importance of restricting PI3K signaling via Akt for proper β-selection kinetics, even though the specific purpose of delaying DP cell maturation remains unknown.10.7554/eLife.10786.015Figure 11.Antagonistic signaling by PI3K and Itpkb controls the kinetics and Notch-dependence of β-selection.

Bottom Line: Here, we show that this Notch-dependence is established through antagonistic signaling by the pre-TCR/Notch effector, phosphoinositide 3-kinase (PI3K), and by inositol-trisphosphate 3-kinase B (Itpkb).This is reversed by inhibition of Akt, mTOR or glucose metabolism.Thus, non-canonical PI3K-antagonism by Itpkb restricts pre-TCR induced metabolic activation to enforce coincidence-detection of pre-TCR expression and Notch-engagement.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, United States.

ABSTRACT
β-selection is the most pivotal event determining αβ T cell fate. Here, surface-expression of a pre-T cell receptor (pre-TCR) induces thymocyte metabolic activation, proliferation, survival and differentiation. Besides the pre-TCR, β-selection also requires co-stimulatory signals from Notch receptors - key cell fate determinants in eukaryotes. Here, we show that this Notch-dependence is established through antagonistic signaling by the pre-TCR/Notch effector, phosphoinositide 3-kinase (PI3K), and by inositol-trisphosphate 3-kinase B (Itpkb). Canonically, PI3K is counteracted by the lipid-phosphatases Pten and Inpp5d/SHIP-1. In contrast, Itpkb dampens pre-TCR induced PI3K/Akt signaling by producing IP4, a soluble antagonist of the Akt-activating PI3K-product PIP3. Itpkb(-/-) thymocytes are pre-TCR hyperresponsive, hyperactivate Akt, downstream mTOR and metabolism, undergo an accelerated β-selection and can develop to CD4(+)CD8(+) cells without Notch. This is reversed by inhibition of Akt, mTOR or glucose metabolism. Thus, non-canonical PI3K-antagonism by Itpkb restricts pre-TCR induced metabolic activation to enforce coincidence-detection of pre-TCR expression and Notch-engagement.

No MeSH data available.


Related in: MedlinePlus