Department of Chemistry & Biochemistry, Florida Atlantic University, Boca Raton, Florida 33431, USA.
J Biol Chem. 2010 Dec 24;285(52):40673-80. doi: 10.1074/jbc.M110.171397. Epub 2010 Oct 5.
Crustacean cardioactive peptide (CCAP) and related peptides are multifunctional regulatory neurohormones found in invertebrates. We isolated a CCAP-related peptide (conoCAP-a, for cone snail CardioActive Peptide) and cloned the cDNA of its precursor from venom of Conus villepinii. The precursor of conoCAP-a encodes for two additional CCAP-like peptides: conoCAP-b and conoCAP-c. This multi-peptide precursor organization is analogous to recently predicted molluscan CCAP-like preprohormones, and suggests a mechanism for the generation of biological diversification without gene amplification. While arthropod CCAP is a cardio-accelerator, we found that conoCAP-a decreases the heart frequency in Drosophila larvae, demonstrating that conoCAP-a and CCAP have opposite effects. Intravenous injection of conoCAP-a in rats caused decreased heart frequency and blood pressure in contrast to the injection of CCAP, which did not elicit any cardiac effect. Perfusion of rat ventricular cardiac myocytes with conoCAP-a decreased systolic calcium, indicating that conoCAP-a cardiac negative inotropic effects might be mediated via impairment of intracellular calcium trafficking. The contrasting cardiac effects of conoCAP-a and CCAP indicate that molluscan CCAP-like peptides have functions that differ from those of their arthropod counterparts. Molluscan CCAP-like peptides sequences, while homologous, differ between taxa and have unique sequences within a species. This relates to the functional hypervariability of these peptides as structure activity relationship studies demonstrate that single amino acids variations strongly affect cardiac activity. The discovery of conoCAPs in cone snail venom emphasizes the significance of their gene plasticity to have mutations as an adaptive evolution in terms of structure, cellular site of expression, and physiological functions.
甲壳动物心脏活性肽（CCAP）和相关肽是在无脊椎动物中发现的多功能调节神经激素。我们从锥螺 Conus villepinii 的毒液中分离出一种 CCAP 相关肽（conoCAP-a，代表锥螺心脏活性肽），并克隆了其前体的 cDNA。conoCAP-a 的前体编码另外两种 CCAP 样肽：conoCAP-b 和 conoCAP-c。这种多肽前体组织类似于最近预测的软体动物 CCAP 样前激素，表明了在不进行基因扩增的情况下产生生物多样性的机制。虽然节肢动物 CCAP 是心脏加速剂，但我们发现 conoCAP-a 降低了果蝇幼虫的心率，表明 conoCAP-a 和 CCAP 具有相反的作用。在大鼠中静脉注射 conoCAP-a 会导致心率和血压降低，而 CCAP 的注射则不会引起任何心脏效应。用 conoCAP-a 灌注大鼠心室心肌细胞会降低收缩期钙，表明 conoCAP-a 的负性肌力作用可能是通过损害细胞内钙转运来介导的。conoCAP-a 和 CCAP 的心脏作用相反表明，软体动物 CCAP 样肽的功能与其节肢动物对应物不同。虽然软体动物 CCAP 样肽序列具有同源性，但在不同的分类群之间存在差异，并且在同一物种内具有独特的序列。这与这些肽的功能高变异性有关，因为结构活性关系研究表明，单个氨基酸的变化会强烈影响心脏活动。在锥螺毒液中发现 conoCAPs 强调了它们基因可塑性的重要性，因为突变是一种结构、细胞表达部位和生理功能的适应性进化。
