Instituto de Biología Molecular y Celular del Cáncer, Centro de Investigación del Cáncer, CSIC-Universidad de Salamanca, Campus Miguel de Unamuno, Salamanca, Spain.
Autophagy. 2012 Nov;8(11):1557-76. doi: 10.4161/auto.21315. Epub 2012 Aug 9.
L-arginine (L-Arg) deficiency results in decreased T-cell proliferation and impaired T-cell function. Here we have found that L-Arg depletion inhibited expression of different membrane antigens, including CD247 (CD3ζ), and led to an ER stress response, as well as cell cycle arrest at G(0)/G(1) in both human Jurkat and peripheral blood mitogen-activated T cells, without undergoing apoptosis. By genetic and biochemical approaches, we found that L-Arg depletion also induced autophagy. Deprivation of L-Arg induced EIF2S1 (eIF2α), MAPK8 (JNK), BCL2 (Bcl-2) phosphorylation, and displacement of BECN1 (Beclin 1) binding to BCL2, leading to autophagosome formation. Silencing of ERN1 (IRE1α) prevented the induction of autophagy as well as MAPK8 activation, BCL2 phosphorylation and XBP1 splicing, whereas led T lymphocytes to apoptosis under L-Arg starvation, suggesting that the ERN1-MAPK8 pathway plays a major role in the activation of autophagy following L-Arg depletion. Autophagy was required for survival of T lymphocytes in the absence of L-Arg, and resulted in a reversible process. Replenishment of L-Arg made T lymphocytes to regain the normal cell cycle profile and proliferate, whereas autophagy was inhibited. Inhibition of autophagy by ERN1, BECN1 and ATG7 silencing, or by pharmacological inhibitors, promoted cell death of T lymphocytes incubated in the absence of L-Arg. Our data indicate for the first time that depletion of L-Arg in T lymphocytes leads to a reversible response that preserves T lymphocytes through ER stress and autophagy, while remaining arrested at G(0)/G(1). Our data also show that the L-Arg depletion-induced ER stress response could lead to apoptosis when autophagy is blocked.
精氨酸（L-Arg）缺乏会导致 T 细胞增殖减少和功能受损。在这里，我们发现 L-Arg 耗尽会抑制不同膜抗原的表达，包括 CD247（CD3ζ），并导致内质网应激反应以及人 Jurkat 和外周血有丝分裂原激活的 T 细胞在 G0/G1 期的细胞周期停滞，而不会发生细胞凋亡。通过遗传和生化方法，我们发现 L-Arg 耗尽也会诱导自噬。剥夺 L-Arg 会诱导 EIF2S1（eIF2α）、MAPK8（JNK）、BCL2（Bcl-2）磷酸化，并导致 BECN1（Beclin 1）与 BCL2 的结合解离，从而形成自噬体。ERN1（IRE1α）沉默可防止自噬的诱导以及 MAPK8 的激活、BCL2 磷酸化和 XBP1 的剪接，而在 L-Arg 饥饿下会导致 T 淋巴细胞凋亡，这表明 ERN1-MAPK8 途径在 L-Arg 耗尽后自噬的激活中起主要作用。自噬是 T 淋巴细胞在缺乏 L-Arg 时存活所必需的，并且是一个可逆的过程。L-Arg 的补充使 T 淋巴细胞恢复正常的细胞周期谱并增殖，而自噬被抑制。ERN1、BECN1 和 ATG7 的沉默或通过药理学抑制剂抑制自噬，会促进在缺乏 L-Arg 的情况下孵育的 T 淋巴细胞的细胞死亡。我们的数据首次表明，T 淋巴细胞中 L-Arg 的耗竭会导致一种可逆的反应，通过内质网应激和自噬来保护 T 淋巴细胞，同时使其停留在 G0/G1 期。我们的数据还表明，当自噬被阻断时，L-Arg 耗竭诱导的内质网应激反应可能导致细胞凋亡。
