Heterogeneous RNA-binding protein M4 is a receptor for carcinoembryonic antigen in Kupffer cells.

Here we report the isolation of the recombinant cDNA clone from rat macrophages, Kupffer cells (KC) that encodes a protein interacting with carcinoembryonic antigen (CEA). To isolate and identify the CEA receptor gene we used two approaches: screening of a KC cDNA library with a specific antibody and the yeast ...
two-hybrid system for protein interaction using as a bait the N-terminal part of the CEA encoding the binding site. Both techniques resulted in the identification of the rat heterogeneous RNA-binding protein (hnRNP) M4 gene. The rat ortholog cDNA sequence has not been previously described. The open reading frame for this gene contains a 2351-base pair sequence with the polyadenylation signal AATAAA and a termination poly(A) tail. The mRNA shows ubiquitous tissue expression as a 2.4-kilobase transcript. The deduced amino acid sequence comprised a 78-kDa membrane protein with 3 putative RNA-binding domains, arginine/methionine/glutamine-rich C terminus and 3 potential membrane spanning regions. When hnRNP M4 protein is expressed in pGEX4T-3 vector system in Escherichia coli it binds (125)I-labeled CEA in a Ca(2+)-dependent fashion. Transfection of rat hnRNP M4 cDNA into a non-CEA binding mouse macrophage cell line p388D1 resulted in CEA binding. These data provide evidence for a new function of hnRNP M4 protein as a CEA-binding protein in Kupffer cells.
Mesh Terms:
Amino Acid Sequence, Animals, Base Sequence, Carcinoembryonic Antigen, Carrier Proteins, Cloning, Molecular, DNA, Complementary, Heterogeneous-Nuclear Ribonucleoproteins, Humans, Kupffer Cells, Male, Molecular Sequence Data, Rats, Rats, Sprague-Dawley, Receptors, Cell Surface, Ribonucleoproteins, Transfection
J. Biol. Chem.
Date: Aug. 17, 2001
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