Insulin receptor substrate-1 (IRS-1) forms a ribonucleoprotein complex associated with polysomes

Abstract

Insulin receptor substrates (IRSs) are known to play important roles in mediating intracellular insulin-like growth factors (IGFs)/insulin signaling. In this study, we identified components of messenger ribonucleoprotein (mRNP) as IRS-1-associated proteins. IRS-1 complex formation analysis revealed that IRS-1 is incorporated into the complexes of molecular mass more than 1000 kDa, which were disrupted by treatment with RNase. Furthermore, oligo(dT) beads precipitated IRS-1 from cell lysates, showing that the IRS-1 complexes contained messenger RNA. Taken together with the data that IRS-1 was fractionated into the polysome-containing high-density fractions, we concluded that IRS-1 forms the novel complexes with mRNPs.

Keywords: 4E binding proteins; 4EBPs; BN-PAGE; DMEM; Dulbecco’s modified Eagle’s medium; EJC; FBS; HEK293; IGFs; IRSs; Insulin receptor substrate; Insulin-like growth factor-I (IGF-I); MALDI-TOF-MS; MAPK; PABPC1; PI3K; PIC; RNA; RNase A; S6 protein kinases; S6Ks; Translation; blue native-polyacrylamide gel electrophoresis; eIF; eukaryotic initiation factor; exon junction complex; fetal bovine serum; human embryonic kidney 293; insulin receptor substrates; insulin-like growth factors; mRNA; mRNP; mTOR; mammalian target of rapamycin; matrix-assisted laser desorption/ionization–time-of-flight mass spectrometry; messenger RNA; messenger ribonucleoprotein; mitogen-activated protein kinase; phosphatidylinositol 3-kinase; poly(A) binding protein cytoplasmic 1; ribonuclease A; ribosomal subunit protein S6; rpS6; translation preinitiation complex.