Beirne B. Carter Center for Immunology Research, University of Virginia, Charlottesville, Virginia 22908, USA.
Nature. 2010 Oct 14;467(7317):863-7. doi: 10.1038/nature09413.
Apoptotic cells release 'find-me' signals at the earliest stages of death to recruit phagocytes. The nucleotides ATP and UTP represent one class of find-me signals, but their mechanism of release is not known. Here, we identify the plasma membrane channel pannexin 1 (PANX1) as a mediator of find-me signal/nucleotide release from apoptotic cells. Pharmacological inhibition and siRNA-mediated knockdown of PANX1 led to decreased nucleotide release and monocyte recruitment by apoptotic cells. Conversely, PANX1 overexpression enhanced nucleotide release from apoptotic cells and phagocyte recruitment. Patch-clamp recordings showed that PANX1 was basally inactive, and that induction of PANX1 currents occurred only during apoptosis. Mechanistically, PANX1 itself was a target of effector caspases (caspases 3 and 7), and a specific caspase-cleavage site within PANX1 was essential for PANX1 function during apoptosis. Expression of truncated PANX1 (at the putative caspase cleavage site) resulted in a constitutively open channel. PANX1 was also important for the 'selective' plasma membrane permeability of early apoptotic cells to specific dyes. Collectively, these data identify PANX1 as a plasma membrane channel mediating the regulated release of find-me signals and selective plasma membrane permeability during apoptosis, and a new mechanism of PANX1 activation by caspases.
凋亡细胞在死亡的早期阶段释放“寻我”信号以招募吞噬细胞。核苷酸 ATP 和 UTP 代表一类“寻我”信号，但它们的释放机制尚不清楚。在这里，我们确定质膜通道 Pannexin 1（PANX1）是凋亡细胞中“寻我”信号/核苷酸释放的介质。药理学抑制和 siRNA 介导的 PANX1 敲低导致凋亡细胞释放核苷酸减少和单核细胞募集减少。相反，PANX1 的过表达增强了凋亡细胞释放核苷酸和吞噬细胞募集。膜片钳记录显示 PANX1 基础上处于非活性状态，并且仅在细胞凋亡期间诱导 PANX1 电流。在机制上，PANX1 本身是效应半胱天冬酶（半胱天冬酶 3 和 7）的靶标，并且 PANX1 内的特定半胱天冬酶切割位点对半胱天冬酶切割位点至关重要在细胞凋亡过程中 PANX1 的功能。表达截断的 PANX1（在假定的半胱天冬酶切割位点）导致持续开放的通道。PANX1 对于早期凋亡细胞对特定染料的“选择性”质膜通透性也很重要。总的来说，这些数据表明 PANX1 是一种质膜通道，可介导凋亡过程中“寻我”信号的调节释放和选择性质膜通透性，以及半胱天冬酶激活 PANX1 的新机制。
