家蚕胰岛素受体类似基因挖掘及在限食模型中的表达特征

家蚕素是家蚕胰岛素相关肽,与其受体(IR)结合激活胰岛素信号转导(IIS)途径。利用生物信息学方法,挖掘出具有胰岛素受体类似结构域的家蚕基因Ir-lp,其ORF长2 658 bp,编码885个氨基酸残基,蛋白质分子质量100.3 kD,pI为6.93,与果蝇等昆虫的同源蛋白保守区域高度一致,NJ法分子进化分析显示家蚕IR-LP与昆虫胰岛素受体相关蛋白同源,但是家蚕Ir-lp编码蛋白缺少胰岛素受体酪氨酸激酶催化结构域,基因表达特征也与已知的家蚕Ir有显著差异。建立家蚕限食模型,调查限食后家蚕8个组织中Ir-lp与Ir表达变化的差异,探讨Ir-lp基因与IIS途径的关系,结果显示长期限食使得Ir-lp与Ir在脂肪体、性腺和表皮中上调表达,在马氏管中下调表达,其中Ir-lp的表达量变化幅度较大。综合分析,IR-LP可能在家蚕胚胎期、蛹期、蛾期等特定发育时期通过与IR竞争结合家蚕素来有效调控能量利用效率。

Excavation of an Insulin Receptor-like Gene and Its Expression Profile Under Dietary Restriction Model in Bombyx mori

Bombyxins are insulin-related peptides in silkworm(Bombyx mori).They can activate the insulin/insulin growth factor signaling(IIS) pathway by binding with insulin receptor(IR).A silkworm gene Ir-lp with insulin receptor-like domain was excavated from silkworm databases by means of bioinformatics.This gene has an open reading frame(ORF) of 2 658 bp and encodes 885 amino acids with predicted molecular mass of 100.3 kD and isoelectric point of 6.93.The conservative regions of silkworm Ir-lp and its homologous proteins from Drosophila melanogaster and other insects are in high consensus.Phylogenetic tree constructed using neighbor joining algorithm showed that silkworm IR-LP is homologous with insulin receptor-related proteins from other insects.However,the silkworm Ir-lp encoded protein lacks the tyrosine kinase catalytic domain and the expression profile of Ir-lp has significant difference with that of known silkworm Ir gene.To explore the relationship between Ir-lp and IIS pathway,we built a silkworm model of dietary restriction to investigate the difference of expression levels of Ir-lp and Ir genes in 8 different silkworm tissues after dietary restriction.The results showed that long-term dietary restriction led to an up-regulation of Ir-lp and Ir genes in fat body,gonad and integument and a down-regulation in Malpighian tubule.Moreover,Ir-lp had a greater range of expressional variations.Taken together,it is suggested that IR-LP could effectively regulate energy utilization efficiency through competing with IR to bind bombyxin during specific developmental stages such as embryonic,pupal and adult stages.