The mTOR Kinase Determines Effector versus Memory CD8+ T Cell Fate by Regulating the Expression of Transcription Factors T-bet and Eomesodermin

“It is possible that mTOR, which has been shown to tether several transcriptional factors (both activators and repressors) (Wullschleger et al., 2006) may regulate T-bet expression based on its activity.”

“Although the kinase mTOR has been implicated as an integrator of various extracellular signals and a sensor for internal energy levels for determination of cell fate (Hay and Sonenberg, 2004), the role for mTOR in integrating instructions that program naive CD8 T cells for type I effector differentiation is unclear.”

“The transcription factor T-bet (Tbx21) is the master regulator of type I effector differentiation whose expression is considerably enhanced and sustained in the presence of IL-12 (Joshi et al., 2007; Szabo et al., 2000).”

“Rapamycin-Treated IL-12-Conditioned OT-I Cells Demonstrate Augmented Tumor Efficacy The use of ex vivo generated tumor-antigen-specific effector CD8 T cells in adoptive cell transfer (ACT) has produced tumor regressions in the clinical setting (Morgan et al., 2006).”

“In agreement, with the reported role for mTOR in regulating cell size (Schmelzle and Hall, 2000) and the expression of L-type amino acid transporter (CD98) (Cornish et al.”

“We performed phenotypic analysis of OT-I cells using markers associated with memory precursor CD8+ T cells, i.e., CD62L (lymph node homing) (Wherry et al., 2003), CD69 (lymph node retention) (Shiow et al., 2006), CD127 (IL-7Ra; essential for memory T cell maintenance) (Schluns et al., 2000), CD122…”

“Several transcription factors have been shown to coordinate and regulate the balance between long-lived memory and terminally differentiated effector CD8+ T cells (Intlekofer et al., 2005; Joshi et al., 2007; Welsh, 2009).”

“…node homing) (Wherry et al., 2003), CD69 (lymph node retention) (Shiow et al., 2006), CD127 (IL-7Ra; essential for memory T cell maintenance) (Schluns et al., 2000), CD122 (IL-15Rb and essential for memory CD8+ T cell homeostatic renewal) (Schluns et al., 2002), KLRG1 (inversely corelated…”

“…reports have demonstrated the role of mTOR in regulating CD8+ T cell trafficking (Sinclair et al., 2008) and memory differentiation (Araki et al., 2009; Pearce et al., 2009), but the molecular mechanisms by which mTOR regulates CD8+ T cell differentiation or trafficking remain uncharacterized.”

“Based on the type of cytokine present during antigen stimulation, naive T cells could give rise to either type I (interferon-g [IFN-g]), type II (interleukin-4 [IL-4]), type 17 (interleukin-17 [IL-17]), or regulatory (transforming growth factor-b [TGF-b], interleukin-10 [IL-10]) functional outcomes, but the instructio…”

“Several transcription factors have been shown to coordinate and regulate the balance between long-lived memory and terminally differentiated effector CD8+ T cells (Intlekofer et al., 2005; Joshi et al., 2007; Welsh, 2009).”

“Moreover, a recent report has implicated the requirement of mTOR kinase signaling in regulating effector versus regulatory cell lineage commitment in CD4 T cells (Delgoffe et al., 2009).”

“…using markers associated with memory precursor CD8+ T cells, i.e., CD62L (lymph node homing) (Wherry et al., 2003), CD69 (lymph node retention) (Shiow et al., 2006), CD127 (IL-7Ra; essential for memory T cell maintenance) (Schluns et al., 2000), CD122 (IL-15Rb and essential for memory CD8+ T…”

“The nature and intensity of instructions received by a naive CD8 T cell orchestrates gene programs that guide their differentiation into various functional subsets (Iezzi et al., 1998; Joshi et al., 2007).”

“The ability of IL-12 to instruct CD8 T cells for robust effector maturation requires STAT4 transcription factor (Jacobson et al., 1995; Li et al., 2006).”

“Instructions received by a naive CD8+ T cell imprint differentiation into short-lived effectors and/or long-lived memory fates by regulating gene programs governed by master transcriptional factors (Kaech and Wherry, 2007).”

“, 2000), CD122 (IL-15Rb and essential for memory CD8 T cell homeostatic renewal) (Schluns et al., 2002), KLRG1 (inversely corelated with memory CD8 T cell generation) (Joshi et al.”

“T cells for effector and memory functions ( Curtsinger et al., 2003; Xiao et al., 2009).”

“inhibitor of mTOR) is widely used to restrict allograft rejection reactions (Saunders et al., 2001), and most mechanistic studies to date have been focused on understanding the action of rapamycin on CD4 T cell responses.”

“…cellular energy status and the energy-sensitive kinase mTOR have been implicated in T cell activation and anergy and survival (Araki et al., 2009; Cham and Gajewski, 2005; Delgoffe et al., 2009; Pearce et al., 2009), we predicted that the mTOR kinase activity is instrumental to the integration…”

“increased expression in memory T cells) (Grayson et al., 2000).”

“The closely related transcription factors T-bet and Eomesodermin are inversely regulated in effector and memory CD8 T cells (Takemoto et al., 2006).”

“The selective ability of rapamycin to inhibit IFN-g production in the secondary (144 hr and 168 hr), but not the primary (72 hr), phase of antigen stimulation was perplexing, but it’s interesting to note that rapamycin treatment did not affect the expression of homeobox transcription factor Hlx (data not shown), which…”

“These studies have demonstrated that mTOR inhibition by rapamycin induces CD4+ T cell anergy and/or differentiation into (FoxP3+) regulatory T cells (Kang et al., 2008; Zheng et al., 2007).”

“The presence of cytokines during antigen stimulation is instrumental in regulating the transcriptional program of CD8 T cells for effector and memory functions (Curtsinger et al., 2003; Xiao et al., 2009).”

“Because some studies suggest that type I IFNs (IFN-a and IFN-b), like IL-12, can also promote type I effector CD8+ T cell responses (Agarwal et al., 2009), we determined whether IFN-a could also regulate mTOR activity and T-bet expression in OT-I cells.”

“In agreement, with the reported role for mTOR in regulating cell size (Schmelzle and Hall, 2000) and the expression of L-type amino acid transporter (CD98) (Cornish et al., 2006), the induction of blast transformation and CD98 expression in Ag+B7.”

“1-, and IL-12-induced phosphoinositide 3-kinase (PI3K)-Akt kinase pathway (Yoo et al., 2002) is required for mTOR signaling in CD8+ T cells.”

“These studies have demonstrated that mTOR inhibition by rapamycin induces CD4+ T cell anergy and/or differentiation into (FoxP3+) regulatory T cells (Kang et al., 2008; Zheng et al., 2007).”

“Emerging insights into CD8 T cell memory generation demonstrates the variety of pathways that can give rise to memory cells (Kaech and Wherry, 2007; Lefrançois and Marzo, 2006).”

“The retroviral vector, T-bet-ER (T-bet-ER RV), was employed wherein the expression of T-bet is regulated by tamoxifen Immunity 32, 67–78, January 29, 2010 ª2010 Elsevier Inc. 71 (4-HT) (Matsuda et al., 2007).”

“The ability of IL-12 to instruct CD8 T cells for robust effector maturation requires STAT4 transcription factor (Jacobson et al., 1995; Li et al., 2006).”

“1 as described previously (Goldberg et al., 2003).”

“Several transcription factors have been shown to coordinate and regulate the balance between long-lived memory and terminally differentiated effector CD8+ T cells (Intlekofer et al., 2005; Joshi et al., 2007; Welsh, 2009).”

“Consistent with this, the drug rapamycin, which also inhibits mTORC1, enhances the generation of CD8 TM cells (17, 19, 20).”

“Moreover, mTOR controls the development of CD8 + memory T cells in part by regulating expression of the transcription factors T-bet and eomesodermi”

“Mechanistically, IL-12 promotes effector CD8 + T cell differentiation through the induction of T-bet (Joshi et al., 2007; Takemoto et al., 2006) via an mTOR-dependent pathway (Rao et al., 2010).”