Meeting Abstract

P1.111  Sunday, Jan. 4  Rainbow trout insulin receptors: cloning, patterns of mRNA expression, and regulation by fasting CARUSO, M.A.*; KITTILSON, J.D.; BLAUFUS , P.C.; SHERIDAN, M.A.; North Dakota St. Univ. Michael.Caruso@ndsu.edu

Insulin (INS) plays a critical role in the growth, development, and metabolism of vertebrates. In this study, a unique cDNA encoding a fourth insulin receptor subtype (IR4) was isolated, cloned and sequenced from the liver of rainbow trout. A 1525-bp cDNA encoding a partial amino acid sequence of the beta-subunit and the 3′ untranslated region (UTR) was obtained. IR4 shares 75.5%, 73.1%, 68.3% deduced amino acid identity with previously characterized trout IR1, IR2, IR3, respectively. Quantitative real-time PCR revealed that the four IR mRNAs were differentially expressed, both in terms of distribution among tissues as well as in terms of abundance within selected tissues of juvenile trout. IR1 mRNA was most abundant in muscle (white, red, cardiac) but least abundant in adipose, whereas IR3 and IR 4 mRNA were most abundant in adipose and liver. All IR subtypes were detected over the course of embryonic development; levels of IR3 and IR4 remained relative constant from pre-hatch (29 days post-fertilization, dpf) to post-hatch (90 dpf), whereas levels of IR1 and IR2 tended to increase during this period. Fasting for 4-6 weeks increased the expression of IR1 and IR4 in liver and cardiac muscle. These findings provide insight into the evolution of IRs as well as into the pattern and regulation of IR expression. (Supported by NSF IOB 0444860 to M.A.S.)