Akt1, Akt2 and Akt3 are members of a family of serine/threonine kinases that are key effectors of PI3K. The Akt family has been well characterized to promote cell survival, glucose metabolism and proliferation in many cell types including developing T cells. Thymocytes express all Akt isoforms to varying degrees. Ablation of single or multiple Akt genes results in differential blocks in T cell development. Loss of all three Akt isoforms leads to an early developmental defect due to decreased survival of CD4?CD8? double negative (DN) thymocytes. Expression of Akt2 or Akt3 alone is sufficient to preserve DN survival; however, DN3 differentiation and DN4 thymocyte proliferation remain defective along with survival of cells at later developmental stages. These distinct phenotypes suggest either that different Akt isoforms regulate distinct functions or that different doses of Akt activity are required to promote stage-specific cell survival, proliferation and differentiation. With no current evidence for isoform-specific functions, we focused our attention on characterizing mechanisms for regulating the dose of Akt activity. Surface receptors, including (pre-)T cell receptor and cytokine receptors, activate PI3K to generate PIP3. Interactions between PIP3 and the Pleckstrin homology (PH) domain of Akt are required to recruit Akt to the plasma membrane for activation. Thus, fine control of PI3K activity and PIP3 availability can directly regulate Akt activation levels. This application addresses an increasingly important alternative mechanism for indirectly controlling Akt activity: via generation of IP4, a soluble inositol polyphosphate that is structurally similar to PIP3. IP4 is generated following (pre)TCR stimulation and competes with PIP3 for binding to the Akt PH domain. Thymocytes deficient in IP4 activate Akt excessively following expression of preTCR at the DN3 and DN4 stages. Strikingly, Akt hyperactivity leads to accelerated ? selection, premature reprogramming to glycolytic metabolism and loss of Notch dependency. This leads us to propose the global hypotheses that 1) preTCR- induced IP4 generation restricts Akt-dependent metabolic reprogramming and proliferation to ensure adequate Notch signaling and 2) preTCR and Notch cooperative signaling is required for T cell lineage specification. Successful completion of this study will shift our current understanding of T lineage specification by revealing 1) an unexpected requirement for preTCR in imposing a Notch checkpoint and in co-stimulating Notch function, 2) a novel preTCR feedback mechanism that controls DN thymocyte proliferation/maturation via tuning of Akt activity and metabolic reprogramming; and 3) a non-canonical pathway for activating TCF1-dependent transcription to specify T cell commitment.

Public Health Relevance

Deficiency in Itpkb and its product IP4 results in an immunodeficiency disease caused by a defect in T cell development. This proposal will examine how preTCR-induced IP4 generation couples with signals generated by the cell-fate regulator Notch to control Akt activity to promote proper T cell development. We will also characterize NDRG3 as a novel Akt effector that may control the decision of progenitors to develop into T cells.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI089805-10
Application #
9841874
Study Section
Cellular and Molecular Immunology - A Study Section (CMIA)
Program Officer
Prabhudas, Mercy R
Project Start
2011-02-15
Project End
2021-12-31
Budget Start
2020-01-01
Budget End
2020-12-31
Support Year
10
Fiscal Year
2020
Total Cost
Indirect Cost
Name
Dartmouth College
Department
Pathology
Type
Schools of Medicine
DUNS #
041027822
City
Hanover
State
NH
Country
United States
Zip Code
03755
Malik, Brian T; Byrne, Katelyn T; Vella, Jennifer L et al. (2017) Resident memory T cells in the skin mediate durable immunity to melanoma. Sci Immunol 2:
Hampsch, Riley A; Shee, Kevin; Bates, Darcy et al. (2017) Therapeutic sensitivity to Rac GTPase inhibition requires consequential suppression of mTORC1, AKT, and MEK signaling in breast cancer. Oncotarget 8:21806-21817
Li, Na; Xu, Wenwen; Yuan, Ying et al. (2017) Immune-checkpoint protein VISTA critically regulates the IL-23/IL-17 inflammatory axis. Sci Rep 7:1485
Xu, Xiaolu; Wang, Xinxin; Todd, Elizabeth M et al. (2016) Mst1 Kinase Regulates the Actin-Bundling Protein L-Plastin To Promote T Cell Migration. J Immunol 197:1683-91
Westernberg, Luise; Conche, Claire; Huang, Yina Hsing et al. (2016) Non-canonical antagonism of PI3K by the kinase Itpkb delays thymocyte ?-selection and renders it Notch-dependent. Elife 5:
Wang, Xinxin; Hills, Leonard Benjamin; Huang, Yina Hsing (2015) Lipid and Protein Co-Regulation of PI3K Effectors Akt and Itk in Lymphocytes. Front Immunol 6:117
Liu, Jun; Yuan, Ying; Chen, Wenna et al. (2015) Immune-checkpoint proteins VISTA and PD-1 nonredundantly regulate murine T-cell responses. Proc Natl Acad Sci U S A 112:6682-7
Clancy-Thompson, Eleanor; Perekslis, Thomas J; Croteau, Walburga et al. (2015) Melanoma Induces, and Adenosine Suppresses, CXCR3-Cognate Chemokine Production and T-cell Infiltration of Lungs Bearing Metastatic-like Disease. Cancer Immunol Res 3:956-67
Lubman, Olga Y; Cella, Marina; Wang, Xinxin et al. (2014) Rodent herpesvirus Peru encodes a secreted chemokine decoy receptor. J Virol 88:538-46
Wang, Xinxin; Boyken, Scott E; Hu, Jiancheng et al. (2014) Calmodulin and PI(3,4,5)P? cooperatively bind to the Itk pleckstrin homology domain to promote efficient calcium signaling and IL-17A production. Sci Signal 7:ra74

Showing the most recent 10 out of 12 publications