This project focuses on studying the role of carbohydrate structures in the subunit association and receptor interactions of hCG. A. HF deglycosylated asialo hCG was found to bind with 2-5 fold higher affinity in corpus luteum homogenates and 5-10 fold higher in testis homogenates than hCG. When added to granulosa luteal cells or testicular minces it caused no cAMP production at 0.1 microgram/ml and inhibited the production of cAMP by hCG. B. Pure hCG alpha subunit was specifically deglycosylated at Asn78 enzymatically. This subunit when combined with intact hCG beta displayed potency in the rat uterine weight assay and in cAMP and testosterone production in rat Leydig cells similar to HF deglycosylated hCG. C. hCG beta chains isolated from urines of 5 choriocarcinoma patients were compared with those from molar and normal pregnant women by SDS polyacrylamide gel electrophoresis and Western blotting using anti-hCG beta-COOH peptide antiserum. The size found in the choriocarcinoma patients were either larger or smaller than those from molar or normally pregnant women and should permit distinguishing these cases. A triantennary oligosaccharide structure in choriocarcinoma hCG implies different mechanisms of processing in the malignant trophoblast.
