UCL Cancer Institute, University College London, Gower St, London, UK.
University of Texas Southwestern Medical Center, Department of Physiology, Dallas, Texas, USA.
Sci Rep. 2019 Jan 24;9(1):619. doi: 10.1038/s41598-018-37056-x.
TMEM16F is a Ca -gated ion channel that is required for Ca -activated phosphatidylserine exposure on the surface of many eukaryotic cells. TMEM16F is widely expressed and has roles in platelet activation during blood clotting, bone formation and T cell activation. By combining microscopy and patch clamp recording we demonstrate that activation of TMEM16F by Ca ionophores in Jurkat T cells triggers large-scale surface membrane expansion in parallel with phospholipid scrambling. With continued ionophore application,TMEM16F-expressing cells then undergo extensive shedding of ectosomes. The T cell co-receptor PD-1 is selectively incorporated into ectosomes. This selectivity depends on its transmembrane sequence. Surprisingly, cells lacking TMEM16F not only fail to expand surface membrane in response to elevated cytoplasmic Ca, but instead undergo rapid massive endocytosis with PD-1 internalisation. These results establish a new role for TMEM16F as a regulator of Ca activated membrane trafficking.
TMEM16F 是一种 Ca2+门控离子通道，对于许多真核细胞表面的 Ca2+激活的磷脂酰丝氨酸暴露是必需的。TMEM16F 广泛表达，在血小板激活、骨形成和 T 细胞激活中发挥作用。通过结合显微镜和膜片钳记录，我们证明 Jurkat T 细胞中 Ca 离子载体对 TMEM16F 的激活与磷脂翻转平行触发大规模的表面膜扩张。随着持续的离子载体应用，TMEM16F 表达的细胞随后经历大量的外泌体脱落。T 细胞共受体 PD-1 被选择性地纳入外泌体。这种选择性取决于其跨膜序列。令人惊讶的是，缺乏 TMEM16F 的细胞不仅不能响应升高的细胞质 Ca 而扩张表面膜，反而会迅速发生大量的内吞作用，导致 PD-1 内化。这些结果确立了 TMEM16F 作为 Ca2+激活的膜运输调节剂的新作用。
