Evidence for a precursor of the high-affinity metastasis-associated murine laminin receptor.
The high-affinity cellular receptor for the basement membrane component laminin is differentially expressed during tumor invasion and metastasis. A cDNA clone encoding the murine laminin receptor was isolated and identified on the basis of sequence homology to the human laminin receptor [Wewer et al. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 7137-7141]. Primer extension experiments demonstrated that the clone contained the complete 5' sequence of the murine laminin receptor mRNA. RNA blot data demonstrated a single-sized laminin receptor mRNA, approximately 1400 bases long, in human, mouse, and rat. The nascent laminin receptor predicted from the cDNA sequence is 295 amino acids long, with a molecular weight of 33,000, and contains one intradisulfide bridge, a short putative transmembrane domain, and an extracellular carboxy-terminal region which has abundant glutamic acid residues and multiple repeat sequences. The precursor of the laminin receptor is apparently smaller than the 67-kilodalton protein isolated from tissue. The apparent molecular weight on SDS-polyacrylamide gels of the rabbit reticulocyte cell-free translation product of selectively hybridized laminin receptor mRNA is 37,000. Antisera to three different domains of the cDNA-predicted receptor were used to study the relationship between the 37- and 67-kilodalton polypeptides. Antisera to cDNA-deduced synthetic peptides of the receptor immunoprecipitated a 37-kilodalton band both from cell-free translation products and from pulse-labeled cell extracts. On immunoblots of cell extracts, one antisynthetic peptide antiserum recognized only the 67-kilodalton receptor, while another antiserum identified both 37- and 67-kilodalton polypeptides, suggesting a precursor-product relationship between the two polypeptides.
Rao
C N
CN
Laboratory of Pathology, National Cancer Institute, Bethesda, Maryland 20892.
Castronovo
V
V
Schmitt
M C
MC
Wewer
U M
UM
Claysmith
A P
AP
Liotta
L A
LA
Sobel
M E
ME
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000235:genetics; D006801:Humans; D015151:Immunoblotting; D007797:Laminin / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009362:Neoplasm Metastasis; D009690:Nucleic Acid Conformation; D009693:Nucleic Acid Hybridization; D014176:Protein Biosynthesis; D011487:Protein Conformation; D011498:Protein Precursors / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger; D051381:Rats; D011971:Receptors, Immunologic / Q000235:genetics* / Q000378:metabolism; D017474:Receptors, Laminin; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D014407:Tumor Cells, Cultured
D007797:Laminin; D011498:Protein Precursors; D012333:RNA, Messenger; D011971:Receptors, Immunologic; D017474:Receptors, Laminin; D004247:DNA