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.
Bajenova
O V
OV
Department of Surgery, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
Zimmer
R
R
Stolper
E
E
Salisbury-Rowswell
J
J
Nanji
A
A
Thomas
P
P
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002272:Carcinoembryonic Antigen / Q000378:metabolism*; D002352:Carrier Proteins / Q000502:physiology*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D006801:Humans; D007728:Kupffer Cells / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D051381:Rats; D017207:Rats, Sprague-Dawley; D011956:Receptors, Cell Surface; D012261:Ribonucleoproteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D014162:Transfection
D002272:Carcinoembryonic Antigen; D002352:Carrier Proteins; D018076:DNA, Complementary; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D011956:Receptors, Cell Surface; D012261:Ribonucleoproteins; C065686:carcinoembryonic antigen binding protein, human