Glycosylated human growth hormone variant.
The human growth hormone variant (hGH-V) gene is expressed by the syncytiotrophoblastic layer of the human placenta in two forms: hGH-V mRNA encoding a 22 kD protein, and hGH-V2 mRNA which retains intron 4 and is expected to encode a 26 kD protein. There is a predicted N-linked glycosylation site in hGH-V at amino acid 140 that is absent in both hGH-V2 and in the highly homologous normal pituitary GH (hGH-N). Cell lines transfected with the hGH-N gene secrete 22 kD GH and the 20 kD product of an alternatively spliced mRNA, while cell lines transfected with the hGH-V gene secrete three proteins of 22, 24, and 26 kD. To determine whether any of these hGH-V isoforms are glycosylated, the cell lines were grown in the absence and presence of tunicamycin. In addition, conditioned medium from metabolically labelled hGH-V transfected cells was separately digested with peptide:N-glycosidase F and endoglycosidase H. The 26 and 24 kD bands were both absent from the media after tunicamycin treatment and were both sensitive to peptide:N-glycosidase F treatment. Endoglycosidase H digestion resulted in the selective loss of the 24 kD band. These results indicate that hGH-V is partially modified posttranslationally by N-linked glycosylation in a fibroblastic cell line.
Ray
J
J
Department of Human Genetics, University of Pennsylvania, Philadelphia 19103.
Jones
B K
BK
Liebhaber
S A
SA
Cooke
N E
NE
D000818:Animals; D002461:Cell Line, Transformed; D005796:Genes; D014644:Genetic Variation; D006031:Glycosylation; D013006:Growth Hormone / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D051379:Mice; D011233:Precipitin Tests; D014415:Tunicamycin / Q000494:pharmacology
D014415:Tunicamycin; D013006:Growth Hormone