Binding of phosphatidic acid to the protein-tyrosine phosphatase SHP-1 as a basis for activity modulation.
Activation of the SH2 domain-possessing protein-tyrosine phosphatase SHP-1 by acidic phospholipids as phosphatidic acid (PA) has been described earlier and suggested to participate in regulation of SHP-1 activity toward cellular substrates. The mechanism of this activation is poorly understood. Direct binding of phosphatidic acid to recombinant SHP-1 could be demonstrated by measuring the extent of [(14)C]PA binding in a chromatographic assay, by measuring the extent of binding of SHP-1 to PA-coated ELISA plates or silica beads (TRANSIL), and by spectroscopic assays employing fluorescently labeled PA liposomes. In addition to PA, phosphatidylinositol 3,4, 5-trisphosphate (PIP3), dipalmitoylphosphatidylglycerol, phosphatidylinositol 4,5-bisphosphate, and phosphatidylserine (PS) were found to bind to SHP-1, albeit to a lesser extent. A high-affinity binding site for PA and PIP3 was mapped to the 41 C-terminal amino acids of SHP-1. This site was absent from the related protein-tyrosine phosphatase SHP-2 and conferred activation of SHP-1 by PA toward two different substrates at low lipid concentrations. A SHP-1 mutant missing this binding site could, however, still be activated toward phosphorylated myelin basic protein as a substrate at high PA concentrations. This activation is likely to be mediated by a second, low-affinity binding site for PA in the N-terminal part of SHP-1 within the SH2 domains. High-affinity phospholipid binding to the C-terminus of SHP-1 may present a specific mechanism of regulating activity and/or cellular localization.
Frank
C
C
Research Unit "Molecular Cell Biology", Klinikum der Friedrich-Schiller-Universität Jena, Germany.
Keilhack
H
H
Opitz
F
F
Zschörnig
O
O
Böhmer
F D
FD
D000595:Amino Acid Sequence; D001665:Binding Sites; D004789:Enzyme Activation; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D050356:Lipid Metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010712:Phosphatidic Acids / Q000737:chemistry / Q000378:metabolism*; D010748:Phosphopeptides / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D013379:Substrate Specificity; D018909:src Homology Domains
D047908:Intracellular Signaling Peptides and Proteins; D010446:Peptide Fragments; D010712:Phosphatidic Acids; D010748:Phosphopeptides; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases