Lee L T O, Tam J K V, Chan D W, Chow B K C
School of Biological Sciences, University of Hong Kong, Hong Kong, China.
Ann N Y Acad Sci. 2009 Apr;1163:209-14. doi: 10.1111/j.1749-6632.2008.03661.x.
In this article, we report the isolation of a full-length cDNA clone encoding pituitary adenylate cyclase-activating polypeptide (PACAP)/PACAP-related peptide (PRP) from lungfish Protopterus dolloi. When comparing the deduced amino acid sequences, the lungfish PACAP was found to be highly conserved with other vertebrates; however, the PRP shares only lower levels of sequence identity with known PRP sequences. Consistently in phylogenetic analysis, the lungfish PRP, similar to sturgeon PRP, fails to cluster with other PRPs. In addition to the full-length clone, another cDNA encoding a short precursor that lacks the first 32 amino acids of the PRP was also isolated. Interestingly, similar isoforms were also identified in several nonmammalian vertebrates, and it was suggested that exon skipping of PRP/PACAP transcripts was a mechanism that regulated the expression ratio of PACAP to PRP in nonmammalian vertebrates. By real-time PCR, both long and short PRP/PACAP transcripts were found almost exclusively in the brain, and the short isoform is the more abundant transcript (3.7 times more), indicating that PACAP is the major product produced in lungfish brain. The expression patterns of lungfish and previously studied frog PRP/PACAP suggest that the PRP/PACAP gene in the tetrapod lineage may first express in the central nervous system; in the process of evolution, the functions of these peptides diversified and were later found in other tissues.
在本文中，我们报道了从非洲肺鱼（Protopterus dolloi）中分离出一个编码垂体腺苷酸环化酶激活多肽（PACAP）/PACAP相关肽（PRP）的全长cDNA克隆。在比较推导的氨基酸序列时，发现肺鱼的PACAP与其他脊椎动物高度保守；然而，PRP与已知PRP序列的序列同一性水平较低。在系统发育分析中，与鲟鱼PRP类似，肺鱼PRP未能与其他PRP聚类。除了全长克隆外，还分离出另一个编码缺少PRP前32个氨基酸的短前体的cDNA。有趣的是，在几种非哺乳动物脊椎动物中也鉴定出了类似的异构体，并且有人提出PRP/PACAP转录本的外显子跳跃是一种调节非哺乳动物脊椎动物中PACAP与PRP表达比例的机制。通过实时PCR，发现长的和短的PRP/PACAP转录本几乎只存在于大脑中，并且短异构体是更丰富的转录本（多3.7倍），这表明PACAP是肺鱼脑中产生的主要产物。肺鱼和先前研究的青蛙PRP/PACAP的表达模式表明，四足动物谱系中的PRP/PACAP基因可能首先在中枢神经系统中表达；在进化过程中，这些肽的功能多样化，后来在其他组织中也被发现。
