Department of Pathology and Molecular Medicine and Division of Cancer Biology and Genetics, Cancer Research Institute, Queen's University, Kingston, ON, Canada.
Mol Biol Cell. 2012 Oct;23(19):3838-50. doi: 10.1091/mbc.E12-02-0114. Epub 2012 Aug 8.
RET encodes a receptor tyrosine kinase that is essential for spermatogenesis, development of the sensory, sympathetic, parasympathetic, and enteric nervous systems and the kidneys, as well as for maintenance of adult midbrain dopaminergic neurons. RET is alternatively spliced to encode multiple isoforms that differ in their C-terminal amino acids. The RET9 and RET51 isoforms display unique levels of autophosphorylation and have differential interactions with adaptor proteins. They induce distinct gene expression patterns, promote different levels of cell differentiation and transformation, and play unique roles in development. Here we present a comprehensive study of the subcellular localization and trafficking of RET isoforms. We show that immature RET9 accumulates intracellularly in the Golgi, whereas RET51 is efficiently matured and present in relatively higher amounts on the plasma membrane. RET51 is internalized faster after ligand binding and undergoes recycling back to the plasma membrane. This differential trafficking of RET isoforms produces a more rapid and longer duration of signaling through the extracellular-signal regulated kinase/mitogen-activated protein kinase pathway downstream of RET51 relative to RET9. Together these differences in trafficking properties contribute to some of the functional differences previously observed between RET9 and RET51 and establish the important role of intracellular trafficking in modulating and maintaining RET signaling.
RET 编码一种受体酪氨酸激酶，它对精子发生、感觉、交感、副交感和肠神经系统以及肾脏的发育，以及成年中脑多巴胺能神经元的维持都是必不可少的。RET 可通过选择性剪接来编码多种异构体，它们在 C 末端氨基酸上有所不同。RET9 和 RET51 异构体显示出独特的自身磷酸化水平，并与衔接蛋白有不同的相互作用。它们诱导不同的基因表达模式，促进不同水平的细胞分化和转化，并在发育中发挥独特的作用。在这里，我们对 RET 异构体的亚细胞定位和运输进行了全面研究。我们表明，不成熟的 RET9 在高尔基体内积累，而 RET51 则被有效地成熟，并在质膜上以相对较高的量存在。配体结合后，RET51 被更快地内化，并通过再循环回到质膜。RET 异构体的这种不同运输方式导致通过 RET51 下游的细胞外信号调节激酶/丝裂原活化蛋白激酶途径的信号传递更快且持续时间更长，与 RET9 相比。这些运输特性的差异共同导致了之前在 RET9 和 RET51 之间观察到的一些功能差异，并确立了细胞内运输在调节和维持 RET 信号中的重要作用。
