| 19956688 |
Choi J, Oh S, Lee D, Oh HJ, Park JY, Lee SB, Lim DS: Mst1-FoxO signaling protects Naive T lymphocytes from cellular oxidative stress in mice. 196-203.
BACKGROUND: The Ste-20 family kinase Hippo restricts cell proliferation and promotes apoptosis for proper organ development in Drosophila. In C. elegans, Hippo homolog also regulates longevity. The mammalian Ste20-like protein kinase, Mst1, plays a role in apoptosis induced by various types of apoptotic stress. Mst1 also regulates peripheral naive T cell trafficking and proliferation in mice. However, its functions in mammals are not fully understood. METHODOLOGY/PRINCIPAL FINDINGS: Here, we report that the Mst1-FoxO signaling pathway plays a crucial role in survival, but not apoptosis, of naive T cells. In Mst1 (-/-) mice, peripheral T cells showed impaired FoxO1/3 activation and decreased FoxO protein levels. Consistently, the FoxO targets, Sod2 and catalase, were significantly down-regulated in Mst1 (-/-) T cells, thereby resulting in elevated levels of intracellular reactive oxygen species (ROS) and induction of apoptosis. Expression of constitutively active FoxO3a restored Mst1 (-/-) T cell survival. Crossing Mst1 transgenic mice (Mst1 Tg) with Mst1 (-/-) mice reduced ROS levels and restored normal numbers of peripheral naive T cells in Mst1 Tg;Mst1 (-/-) progeny. Interestingly, peripheral T cells from Mst1 (-/-) mice were hypersensitive to gamma-irradiation and paraquat-induced oxidative stresses, whereas those from Mst1 Tg mice were resistant. CONCLUSIONS/SIGNIFICANCE: These data support the hypothesis that tolerance to increased levels of intracellular ROS provided by the Mst1-FoxOs signaling pathway is crucial for the maintenance of naive T cell homeostasis in the periphery. |
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