Functional domains of the 67-kDa laminin receptor precursor.
We report the characterization of two functional domains of the metastasis-associated 67-kDa laminin receptor (67-LR). Using synthetic peptides deduced from the cDNA sequence of the 37-kDa precursor of the laminin receptor (37-LRP) as well as their corresponding affinity-purified polyclonal antibodies, we identified a unique laminin binding site as well as a membrane-associated domain of the receptor. In laminin dot blot and solid phase radioligand assays, a 20 amino acid synthetic peptide (IPCNNKGAHSVGLMWWMLAR, amino acid residues 161-180, designated peptide G) specifically bound to laminin with high affinity (Kd = 5 x 10(-8) M). Peptide G also specifically eluted the 67-LR from a laminin affinity column. Peptide G and laminin reacted with a 1:1 stoichiometry, suggesting that there is one recognition site on laminin for the peptide G domain. Immunofluorescence studies, performed on permeabilized and nonpermeabilized human A2058 melanoma cells using 10 different affinity-purified antibodies to distinct regions of the 37-LRP, identified an unusually short membrane-associated domain that was consistent with a computer predicted transmembrane domain (residues 86-101). Our data demonstrate for the first time that the 37-LRP has two functional domains consistent with the characteristics of the mature 67-LR. Furthermore, we propose peptide G as a potential inhibitor of tumor cell interactions with laminin.
Castronovo
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Tumor Invasion and Metastasis Section, National Cancer Institute, Bethesda, Maryland 20892.
Taraboletti
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Sobel
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D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002846:Chromatography, Affinity; D004247:DNA / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D011869:Radioligand Assay; D011971:Receptors, Immunologic / Q000235:genetics* / Q000378:metabolism; D017474:Receptors, Laminin
D011971:Receptors, Immunologic; D017474:Receptors, Laminin; D004247:DNA