There are two major isoforms of NTRK2 (neurotrophic receptor tyrosine kinase 2, or TrkB), full-length isoform with tyrosine kinase (TK) domain intact (+) and spliced isoform without tyrosine kinase domain (TK(-)). Within each isoform, there exist subtypes with minor modifications of the protein sequences. In human, the NTRK2 mRNA transcripts encoding TK(+) have same 3'UTRs, while the transcripts encoding subtypes of NTRK2 TK(-) have two completely different 3'UTRs. In mouse, the mRNA transcripts encoding same NTRK2 protein sequence for either TK(+) or TK(-) have long or short 3'UTRs, respectively. The physiological functions of these different 3'UTRs are still unknown. Pilocarpine stimulation increased Ntrk2 mRNA levels in soma, while the increase in synaptosome was smaller. FISH results further showed that mouse Ntrk2 transcripts with different 3'UTRs were distributed differently in cultured cortical neurons. The transcripts with long 3'UTR were distributed more in apical dendrites compared with transcripts with short 3'UTR. Our results provide evidence of non-coding 3'UTR function in regulating mRNA distribution in neurons.

中文翻译：

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3'UTR 调节皮质神经元中的小鼠 Ntrk2 mRNA 分布。

NTRK2 有两种主要的异构体（神经营养受体酪氨酸激酶 2，或 TrkB），具有完整的酪氨酸激酶 (TK) 结构域 (+) 的全长异构体和没有酪氨酸激酶结构域的剪接异构体 (TK(-))。在每个同种型中，都存在对蛋白质序列进行微小修饰的亚型。在人类中，编码 TK(+) 的 NTRK2 mRNA 转录物具有相同的 3'UTR，而编码 NTRK2 TK(-) 亚型的转录物具有两个完全不同的 3'UTR。在小鼠中，为 TK(+) 或 TK(-) 编码相同 NTRK2 蛋白序列的 mRNA 转录本分别具有长或短的 3'UTR。这些不同的 3'UTR 的生理功能仍然未知。毛果芸香碱刺激增加了胞体中的 Ntrk2 mRNA 水平，而突触体的增加较小。FISH结果进一步表明具有不同3'UTR的小鼠Ntrk2转录物在培养的皮质神经元中分布不同。与具有短 3'UTR 的转录本相比，具有长 3'UTR 的转录本更多地分布在顶端树突中。我们的结果提供了非编码 3'UTR 功能在调节神经元中 mRNA 分布中的作用的证据。