v-Src induces Shc binding to tyrosine 63 in the cytoplasmic domain of the LDL receptor-related protein 1.
We recently observed that the LDL receptor-related protein 1 (LRP-1) is tyrosine phosphorylated in v-Src-transformed cells. Using a GST-fusion protein containing the cytoplasmic domain of LRP-1, we show that LRP-1 is a direct substrate for v-Src in vitro. To study LRP-1 phosphorylation in vivo, we constructed an LRP-1 minireceptor composed of the beta chain linked at the amino-terminus to a Myc epitope (Myc-LRPbeta). When expressed together with v-Src, Myc-LRPbeta becomes phosphorylated on tyrosine. Of the four tyrosine residues present in the cytoplasmic domain of LRP-1, only Tyr 63 is phosphorylated by v-Src in vivo or in vitro. Using fibroblasts deficient in Src, Yes and Fyn, we were able to show that there are multiple kinases present in the cell that can phosphorylate LRP-1. Tyrosine-phosphorylated LRP-1 associates with Shc, a PTB and SH2 domain containing signaling protein that is involved in the activation of Ras. Binding of the purified Shc PTB domain to Tyr 63 containing peptides shows that the interaction between LRP-1 and Shc is direct. We found that DAB, a PTB domain containing signaling protein that is involved in signaling by LDL receptor-related proteins in the nervous system, did not bind to full-length LRP-1. Our observations suggest that LRP-1 may be involved in normal and malignant signal transduction through a direct interaction with Shc adaptor proteins.
Barnes
Helen
H
Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0601, USA.
Ackermann
Elizabeth J
EJ
van der Geer
Peter
P
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D000939:Epitopes / Q000235:genetics; D016259:Genes, myc / Q000276:immunology; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D015688:Oncogene Protein pp60(v-src) / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D055765:Shc Signaling Adaptor Proteins; D013379:Substrate Specificity; D014443:Tyrosine / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000939:Epitopes; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011506:Proteins; D011993:Recombinant Fusion Proteins; D055765:Shc Signaling Adaptor Proteins; D014443:Tyrosine; D015688:Oncogene Protein pp60(v-src)