Department of Physiology and Immunology, Faculty of Biology, University of Barcelona, Barcelona, Spain.
PLoS One. 2013 Sep 25;8(9):e75349. doi: 10.1371/journal.pone.0075349. eCollection 2013.
Calpains are non-lysosomal calcium-activated neutral proteases involved in a wide range of cellular processes including muscle proteolysis linked to post-mortem flesh softening. The aims of this study were (a) to characterise several members of the calpain system in gilthead sea bream and (b) to examine their expression in relation to nutritional status and muscle tenderisation. We identified the complete open reading frame of gilthead sea bream calpains1-3, sacapn1, sacapn2, sacapn3, and two paralogs of the calpain small subunit1, sacapns1a and sacapns1b. Proteins showed 63-90% sequence identity compared with sequences from mammals and other teleost fishes, and the characteristic domain structure of vertebrate calpains. Transcripts of sacapn1, sacapn2, sacapns1a and sacapns1b had a wide tissue distribution, whereas sacapn3 was almost exclusively detected in skeletal muscle. Next, we assessed transcript expression in skeletal muscle following alteration of nutritional status by (a) fasting and re-feeding or (b) feeding four experimental diets with different carbohydrate-to-protein ratios. Fasting significantly reduced plasma glucose and increased free fatty acids and triglycerides, together with a significant increase in sacapns1b expression. Following 7 days of re-feeding, plasma parameters returned to fed values and sacapn1, sacapn2, sacapns1a and sacapns1b expression was significantly reduced. Furthermore, an increase in dietary carbohydrate content (11 to 39%) diminished growth but increased muscle texture, which showed a significant correlation with decreased sacapn1 and sacapns1a expression, whilst the other calpains remained unaffected. This study has demonstrated that calpain expression is modulated by nutritional status and diet composition in gilthead sea bream, and that the expression of several calpain members is correlated with muscle texture, indicating their potential use as molecular markers for flesh quality in aquaculture production.
钙蛋白酶是一种非溶酶体钙激活中性蛋白酶，参与多种细胞过程，包括与死后肉质软化相关的肌肉蛋白水解。本研究的目的是(a) 研究真鲷钙蛋白酶系统的几个成员，并(b) 研究它们在营养状况和肌肉嫩度方面的表达。我们鉴定了真鲷 calpains1-3、sacapn1、sacapn2、sacapn3 和 calpain 小亚基 1 的两个 paralogs sacapns1a 和 sacapns1b 的完整开放阅读框。与哺乳动物和其他硬骨鱼类的序列相比，这些蛋白质的序列同一性为 63-90%，并且具有脊椎动物钙蛋白酶的特征结构域。sacapn1、sacapn2、sacapns1a 和 sacapns1b 的转录本具有广泛的组织分布，而 sacapn3 几乎仅在骨骼肌中检测到。接下来，我们通过(a) 禁食和再喂食或(b) 喂食四种不同碳水化合物与蛋白质比的实验饲料来评估营养状况改变后骨骼肌中的转录物表达。禁食显著降低了血糖，增加了游离脂肪酸和甘油三酯，同时 sacapns1b 的表达显著增加。再喂食 7 天后，血浆参数恢复到喂养值，sacapn1、sacapn2、sacapns1a 和 sacapns1b 的表达显著降低。此外，增加饮食中碳水化合物含量(11%至 39%)会降低生长速度，但会增加肌肉质地，这与 sacapn1 和 sacapns1a 的表达降低显著相关，而其他钙蛋白酶不受影响。本研究表明，钙蛋白酶的表达受真鲷营养状况和饮食组成的调节，并且几个钙蛋白酶成员的表达与肌肉质地相关，表明它们可作为水产养殖生产中肉质的分子标记。
