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A Novel Feeder-free System for Mass Production of Murine Natural Killer Cells In Vitro
Published on: January 9, 2018
PDK1 orchestrates early NK cell development through induction of E4BP4 expression and maintenance of IL-15
Meixiang Yang1, Dan Li1, Zai Chang1
1School of Medicine, and Center of Animal Facility, Tsinghua University, Beijing 100086, China.
Insights
The kinase PDK1 connects IL-15 signaling to E4BP4, crucial for NK cell development. This pathway regulates NK cell responsiveness and antitumor activity, highlighting a feedback loop essential for immune function.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- E4BP4 is vital for natural killer (NK) cell development.
- The signals inducing E4BP4 expression and its role in NK cell differentiation are not fully understood.
Purpose of the Study:
- To identify the signaling pathway that induces E4BP4 expression during NK cell development.
- To investigate the role of PDK1 in connecting IL-15 signaling to E4BP4 and its impact on NK cell function.
Main Methods:
- Utilized genetic deletion models to study the role of PDK1 in NK cell development.
- Analyzed IL-15 signaling, mTOR activation, E4BP4 induction, and CD122 expression in PDK1-deficient NK cells.
- Investigated the reversibility of observed phenotypes through gene expression and pathway activation.
Main Results:
- Early deletion of PDK1 led to severe NK cell loss and impaired antitumor activity.
- PDK1 deficiency resulted in reduced IL-15-induced mTOR activation and E4BP4 expression.
- PDK1-deficient NK cells showed decreased CD122 levels, impacting IL-15 responsiveness.
- Phenotypes were partially rescued by E4BP4 re-expression or mTOR activation.
Conclusions:
- PDK1 acts as a key mediator linking IL-15 signaling to E4BP4 expression in early NK cell development.
- A positive feedback loop involving PDK1-mTOR-E4BP4-CD122 signaling is critical for NK cell IL-15 self-responsiveness.
- PDK1-mediated metabolic signaling is not essential for terminal NK cell maturation or survival.
Abstract:
E4BP4, a circadian protein, is indispensable for NK cell development. It remains largely unknown which signal is required to induce E4BP4 expression and what effects it has during NK cell differentiation. Here, we reveal that PDK1, a kinase upstream of mTOR, connects IL-15 signaling to E4BP4. Early deletion of PDK1 caused a severe loss of NK cells and compromised antitumor activity in vivo. PDK1-deficient NK cells displayed much weaker IL-15-induced mTOR activation and E4BP4 induction, as well as remarkable reduction in CD122, a receptor subunit specifying NK cell responsiveness to IL-15. The phenotypes were partially reversible by ectopic expression of E4BP4 or bypassed activation of mTOR. We also determined that PDK1-mediated metabolic signaling was dispensable for NK cell terminal maturation and survival. Thus, we identify a role for PDK1 signaling as a key mediator in regulating E4BP4 expression during early NK cell development. Our findings underscore the importance of IL-15 self-responsiveness through a positive feedback loop that involves PDK1-mTOR-E4BP4-CD122 signaling.
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