Identification and characterization of a luteinizing hormone/chorionic gonadotropin (LH/CG) receptor precursor in a human kidney cell line stably transfected with the rat luteal LH/CG receptor complementary DNA.
It is well established that the LH/CG receptor expressed in gonadal cells is an 85- to 92-kilodalton (kDa) glycoprotein. Additionally, however, a number of reports have noted the existence of other putative receptor species, but few attempts have been made to characterize these variant receptor species. A cell line [293L(wt1)] had previously been isolated which expresses large numbers of high affinity cell surface LH/CG receptors. Visualization of the LH/CG receptor species expressed in these cells and in rat luteal cells using ligand blots revealed 85- and 90-kDa LH/CG receptors, respectively, while immunoblots revealed another 68-kDa glycoprotein receptor in both cell types. The presence of both the 85- and 68-kDa receptor species was confirmed using immunoprecipitation and affinity purification of metabolically labeled 293L(wt1) cells. Enzymatic deglycosylations established that the 85-kDa receptor is a sialoprotein, while the 68-kDa species contains exposed high mannose residues. Protease digestion before LH/CG receptor immunoprecipitations localized the 85-kDa receptor on the plasma membrane, while the 68-kDa receptor was shown to be located intracellularly. Pulse-chase experiments were then used to positively establish that the 68-kDa receptor protein is actually a precursor of the 85-kDa LH/CG receptor species.
Hipkin
R W
RW
Department of Pharmacology, University of Iowa College of Medicine, Iowa City 52242.
Sánchez-Yagüe
J
J
Ascoli
M
M
D000818:Animals; D002241:Carbohydrates / Q000032:analysis; D002460:Cell Line; D003338:Corpus Luteum / Q000166:cytology / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D007668:Kidney; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D011967:Receptors, Gonadotropin / Q000235:genetics* / Q000378:metabolism; D011974:Receptors, LH / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics* / Q000378:metabolism; D014162:Transfection
D002241:Carbohydrates; D008562:Membrane Glycoproteins; D011498:Protein Precursors; D011967:Receptors, Gonadotropin; D011974:Receptors, LH; D011993:Recombinant Fusion Proteins