IRS pleckstrin homology domains bind to acidic motifs in proteins.
Using a yeast two-hybrid system, we identified several proteins that interact with the PH domains in IRS-1 and IRS-2, including Lon protease, myeloblast protein, and nucleolin. Although the roles of these molecules in insulin action are not yet known, each protein contained an acidic motif that interacted with the PH domain of IRS-2. However, only the acidic motif in nucleolin bound to IRS-1, suggesting that the PH domain in IRS-1 and IRS-2 are not identical. Moreover, synthetic peptides based on the acidic motif in Lon protease and myeloblast protein inhibited the binding of nucleolin to the PH domain of IRS-2 but not to the PH domain of IRS-1, confirming the selectivity of these PH domains. The ability to bind acidic motifs may be a specific function of the PH domain in IRS proteins, because the PH domains in betaARK, phospholipase Cgamma, or spectrin did not bind nucleolin. In 32D cells, nucleolin bound to both IRS-1 and IRS-2, and expression of the acidic motif of nucleolin inhibited insulin-stimulated tyrosine phosphorylation of IRS-1 and IRS-2. These results suggest that the binding of acidic motifs to the PH domain of IRS-1 and IRS-2 disrupts coupling to the activated insulin receptor. Our results are consistent with the hypothesis that the PH domain in the IRS proteins may ordinarily bind acidic peptide motifs in membrane proteins or other acidic membrane elements that couple IRS proteins to activated membrane receptors.
Burks
D J
DJ
Howard Hughes Medical Institute, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts 02215, USA.
Wang
J
J
Towery
H
H
Ishibashi
O
O
Lowe
D
D
Riedel
H
H
White
M F
MF
D049069:ATP-Dependent Proteases; D000595:Amino Acid Sequence; D000600:Amino Acids, Dicarboxylic; D001665:Binding Sites; D001798:Blood Proteins; D006360:Heat-Shock Proteins / Q000378:metabolism; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D016601:RNA-Binding Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000378:metabolism; D000097796:Nucleolin
D049069:ATP-Dependent Proteases; D000600:Amino Acids, Dicarboxylic; D001798:Blood Proteins; D006360:Heat-Shock Proteins; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D009842:Oligopeptides; D010446:Peptide Fragments; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D012697:Serine Endopeptidases; D000097796:Nucleolin; C039077:platelet protein P47