Spatial differences in active caspase-8 defines its role in T-cell activation versus cell death.
Spatial differences in active caspase-8 defines its role in T-cell activation versus cell death.
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DOI：
10.1038/cdd.2008.100
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发表时间：
2008-11
影响因子：
12.4
通讯作者：
Budd, R. C.
中科院分区：
文献类型：
--
作者：
Koenig, A.;Russell, J. Q.;Rodgers, W. A.;Budd, R. C.
Caspase-8是一种半胱氨酸蛋白酶，当通过死亡受体激活时，会引发细胞凋亡。Caspase-8也是T细胞抗原受体（TCR）信号传导后启动T淋巴细胞增殖所必需的。考虑到这些不同的caspase-8功能，我们试图确定这是否仅代表caspase-8激活程度的差异，还是活性caspase-8在细胞内的不同位置。我们通过高分辨率多色共聚焦激光扫描显微镜证明了活性caspase-8在抗cd3刺激的T细胞的膜脂筏内聚集。这表明在TCR刺激后，活性caspase-8与脂筏蛋白发生物理相互作用，可能形成信号传导平台。相比之下，Fas对T细胞的刺激导致caspase-8的更深刻的激活，这种激活完全是细胞质的。这些共聚焦显微镜的发现被证实使用不连续的蔗糖梯度超离心分离脂筏和细胞质成分。这种caspase-8活化的隔离模型进一步得到了观察结果的支持，即经典的caspase-8底物BID在CD3刺激的T细胞中不被切割，但在Fas参与后被切割。我们的数据支持一个模型，即活性caspase-8的位置可能深刻影响其作为细胞周期或细胞死亡调节剂的功能能力。
Caspase-8, a cysteine-protease, initiates apoptosis when activated via death receptors. Caspase-8 is also essential for initiating T lymphocyte proliferation following T cell antigen receptor (TCR) signaling. Given these disparate functions of caspase-8, we sought to determine whether this represented only a difference in the magnitude of caspase-8 activation, or different intracellular locations of active caspase-8. We demonstrate by high-resolution multi-color confocal laser scanning microscopy an aggregation of active caspase-8 within membrane lipid rafts in T cells stimulated with anti-CD3. This suggests that following TCR stimulation active caspase-8 physically interacts with lipid raft proteins, possibly to form a signaling platform. In contrast, Fas stimulation of T cells resulted in a much more profound activation of caspase-8 that was exclusively cytosolic. These confocal microscopic findings were confirmed using discontinuous sucrose gradient ultracentrifugation to isolate lipid raft versus cytosolic components. This sequestration model of caspase-8 activation was further supported by the observation that a classic caspase-8 substrate, BID, was not cleaved in CD3 stimulated T cells, but was cleaved after Fas engagement. Our data support a model that the location of active caspase-8 may profoundly influence its functional capacity as a regulator of either cell cycling or cell death.
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通讯作者：
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