Mitogenic and receptor activities of human growth hormone 108-129.
We have selectively synthesized a number of peptides encompassing the region of helix 3 of growth hormone (GH). These peptides and native human (h) GH have been evaluated for mitogenic and receptor activities in 3T3-F442A preadipocytes. In this system, wild type hGH is anti-mitogenic. In contrast, hGH 108-129 stimulated DNA synthesis while other GH-derived peptides were ineffective. hGH (L) 108-129 had an EC50 of about 0.2 nM and was maximally effective at about 0.5 nM in stimulating [3H]thymidine incorporation in 3T3-F442A cells. hGH (L) 108-129 was mitogenically as active as insulin-like growth factor-I and more active than insulin. It was less effective than transforming growth factor-beta. By cell cycle analysis, hGH (L) 108-129 increased the proportion of cells in S/G2/M phases to 28%. hGH, when coincubated with hGH (L) 108-129, blocked the mitogenic response of the peptide. A monoclonal antibody to the GH receptor significantly reduced binding of 125I-hGH to its receptor but had no effect on binding of 125I-hGH (L) 108-129. Affinity cross-linking of 125I-hGH to its receptor was not duplicated with 125I-hGH (L) 108-129. No other GH peptides or insulin competed for binding of 125I-hGH 108-129. Scatchard analysis indicated a Kd of 5.2 nM with 5.6 x 10(5) binding sites/cell for hGH (L) 108-129. These studies indicate that hGH (L) 108-129, a sequence encompassing helix 3 of hGH, acts by binding to a site other than the GH receptor and evokes high mitogenic responses.
Jeoung
D I
DI
Memorial Sloan-Kettering Cancer Center, New York, New York.
Allen
D L
DL
Guller
S
S
Yen
V
V
Sonenberg
M
M
D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002453:Cell Cycle / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D013006:Growth Hormone / Q000378:metabolism* / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D010446:Peptide Fragments / Q000378:metabolism* / Q000494:pharmacology*; D011986:Receptors, Somatotropin / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D007328:Insulin; D010446:Peptide Fragments; D011986:Receptors, Somatotropin; D016212:Transforming Growth Factor beta; C083838:somatotropin (108-129); D013006:Growth Hormone; D004247:DNA; D013936:Thymidine