Kobayashi Yuki, Tsuchiya Keisuke, Yamanome Takeshi, Schiöth Helgi B, Kawauchi Hiroshi, Takahashi Akiyoshi
School of Fisheries Sciences, Kitasato University, Ofunato, Iwate 022-0101, Japan.
Gen Comp Endocrinol. 2008 Jan 15;155(2):280-7. doi: 10.1016/j.ygcen.2007.05.010. Epub 2007 May 13.
The melanocortin (MC) system is composed of melanocyte-stimulating hormone, adrenocorticotropic hormone and their receptors. The MC system has a role in both pigmentation and the regulation of energy homeostasis, in which MC4R, one of the five MC receptors, has a key role. Interestingly, the barfin flounder (Pleuronectiformes) reared with a black background shows retarded growth compared to white background-reared fish, which could be associated with the MC system because of its dual role in regulating pigmentation and energy status. Here, we cloned MC4R and assessed the effects of feeding status on its expression in barfin flounder. Barfin flounder MC4R was composed of 325 amino acids and showed the highest sequence identity to MC4R of fugu (85%), followed by rainbow trout (82%), zebrafish (79%), goldfish (78%), dogfish (71%), chickens (67%), humans (67%) and mice (65%). Among 18 different tissues examined, the predominant expression of MC4R was observed in the brain, liver, testis and ovary as detected with reverse transcription PCR. Food deprivation resulted in a 4-fold increase in the number of MC4R transcripts in the liver, whereas no change was observed in the brain between fasted fish and fed controls. These results suggest that the MC system including MC4R is associated with energy homeostasis in barfin flounder and that peripheral tissues could play a role in this regulation.
黑皮质素（MC）系统由促黑素、促肾上腺皮质激素及其受体组成。MC系统在色素沉着和能量稳态调节中均发挥作用，其中五种MC受体之一的MC4R起着关键作用。有趣的是，与饲养在白色背景下的鱼相比，饲养在黑色背景下的条斑星鲽（鲽形目）生长迟缓，这可能与MC系统有关，因为它在调节色素沉着和能量状态方面具有双重作用。在此，我们克隆了MC4R，并评估了摄食状态对其在条斑星鲽中表达的影响。条斑星鲽MC4R由325个氨基酸组成，与河豚的MC4R序列一致性最高（85%），其次是虹鳟（82%）、斑马鱼（79%）、金鱼（78%）、角鲨（71%）、鸡（67%）、人类（67%）和小鼠（65%）。在检测的18种不同组织中，通过逆转录PCR检测到MC4R在脑、肝、睾丸和卵巢中主要表达。饥饿导致肝脏中MC4R转录本数量增加4倍，而在饥饿鱼和喂食对照的脑中未观察到变化。这些结果表明，包括MC4R在内的MC系统与条斑星鲽的能量稳态相关，并且外周组织可能在这种调节中发挥作用。
