Department of Animal Science, The Ohio State University, Columbus 43210, USA.
J Anim Sci. 2011 Nov;89(11):3490-500. doi: 10.2527/jas.2011-3897. Epub 2011 Jun 3.
Adipose triglyceride lipase (ATGL) is the rate-limiting enzyme of lipolysis in chicken adipose tissue. Its regulation is not fully understood. Recent studies suggest ATGL may be regulated by physical protein-protein interactions. Comparative gene identification 58 (CGI-58) has been identified as an activator of ATGL in mice. The purpose of the current study was to clone and sequence the CGI-58 gene in avian species and to investigate its regulation during development, fasting, and refeeding. Here, we report the cloning and sequencing of the complete coding sequence of CGI-58 and the deduced AA sequences for the domestic chicken, turkey, and Coturnix quail. The CGI-58 protein is a 343-AA protein in the chicken and quail, and a 344-AA protein in the turkey. Sequence comparisons with the human and mouse show that the CGI-58 gene is highly conserved among avian and mammalian species, with complete identities at the predicted lipid-binding site. Cell fractionation of chicken fat cells and stromal-vascular cells revealed that CGI-58 is expressed primarily in mature adipocytes (P < 0.01). When compared in multiple organs and tissues, avian CGI-58 is expressed predominantly in the adipose tissue (P < 0.001), similar to ATGL. To understand CGI-58 expression during adipose tissue development, its mRNA expression was measured along with ATGL and stearoyl CoA desaturase (SCD-1) mRNA, an adipogenic marker, in embryos and adults. Messenger RNA expression of CGI-58 increased (P < 0.05) immediately after hatching, concurrent with peak ATGL expression. It is interesting that CGI-58 remained somewhat increased at posthatch d 11 and 33 as SCD-1 mRNA expression increased (P < 0.05). To evaluate the response of CGI-58 to nutritional status, chickens and quail were fasted for 24 h and subsequently refed. After the fasting period, CGI-58 mRNA was induced (P < 0.05) for both chickens and quail and was returned to control levels upon refeeding. The ATGL mRNA responded similarly, increasing dramatically after fasting and quickly decreasing with refeeding. The direct relationship between CGI-58 and ATGL mRNA expression indicates a role for CGI-58 in activating ATGL-mediated lipolysis in avian species.
脂肪甘油三酯脂肪酶（ATGL）是鸡脂肪组织中脂肪分解的限速酶。其调节机制尚不完全清楚。最近的研究表明，ATGL 可能受物理蛋白-蛋白相互作用的调节。比较基因鉴定 58（CGI-58）已被确定为小鼠 ATGL 的激活剂。本研究的目的是克隆和测序禽类物种的 CGI-58 基因，并研究其在发育、禁食和再喂养过程中的调节作用。在这里，我们报道了鸡、火鸡和鹌鹑的 CGI-58 基因的全长编码序列的克隆和测序，以及推导的 AA 序列。鸡和鹌鹑的 CGI-58 蛋白是一种 343-AA 蛋白，火鸡的 CGI-58 蛋白是一种 344-AA 蛋白。与人类和小鼠的序列比较表明，CGI-58 基因在禽类和哺乳动物物种中高度保守，在预测的脂质结合位点完全一致。鸡脂肪细胞和基质血管细胞的细胞分离显示，CGI-58 主要在成熟脂肪细胞中表达（P < 0.01）。在多个器官和组织中比较时，禽类 CGI-58 主要在脂肪组织中表达（P < 0.001），与 ATGL 相似。为了了解 CGI-58 在脂肪组织发育过程中的表达情况，我们测量了胚胎和成年时期其 mRNA 表达与 ATGL 和硬脂酰辅酶 A 去饱和酶（SCD-1）mRNA 的关系，SCD-1mRNA 是一种脂肪生成标记物。CGI-58 的信使 RNA 表达在孵化后立即增加（P < 0.05），与 ATGL 表达的峰值同时发生。有趣的是，CGI-58 在孵化后第 11 天和第 33 天随着 SCD-1mRNA 表达的增加（P < 0.05）仍略有增加。为了评估 CGI-58 对营养状况的反应，鸡和鹌鹑禁食 24 小时，然后再喂食。禁食期后，鸡和鹌鹑的 CGI-58mRNA 均被诱导（P < 0.05），再喂食后恢复到对照水平。ATGLmRNA 的反应类似，禁食后急剧增加，再喂食后迅速减少。CGI-58 和 ATGLmRNA 表达之间的直接关系表明，CGI-58 在激活禽类物种中 ATGL 介导的脂肪分解中起作用。
