A method to increase the number of growth hormone receptors at the surface of cells.
The number of growth hormone receptors (GHRs) per cell are regulated and this feature plays a major role in the hormone responsiveness of the body. We previously observed in transfected Chinese hamster lung cells that GHR availability is determined by three factors: endocytosis (75%), shedding (10%), and other undetermined mechanisms (15%). The endocytosis depends on an active ubiquitin conjugation system. In addition, this process is ligand-independent. Here, we show that this principle is useful to increase the abundance of GHRs at the cell surface of cells using a combination of inhibitors. In theory, an inhibitor that targets the ubiquitin conjugation specific for the GHR, would suffice, as almost 80% of the removal rate depends on this mechanism. As the molecular mechanism is unknown yet, we used a general inhibitor of proteasome action. Unfortunately, such an inhibitor stimulates the shedding process severalfold. Our data show that the combination of a general proteasome inhibitor and a matrix metalloprotease inhibitor results in an almost twofold increase in functional GHRs at the cell surface, and generate new perspectives to increase the sensitivity of cells for growth hormone.
van Kerkhof
Peter
P
Department of Cell Biology and Institute of Biomembranes, University Medical Centre Utrecht, Heidelberglaan 100, AZU-G02.525, The Netherlands.
Vallon
Erica
E
Strous
Ger J
GJ
D016475:3T3 Cells / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells / Q000187:drug effects / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D013006:Growth Hormone / Q000378:metabolism; D006801:Humans; D008024:Ligands; D061965:Matrix Metalloproteinase Inhibitors; D051379:Mice; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors; D011480:Protease Inhibitors / Q000494:pharmacology*; D046988:Proteasome Endopeptidase Complex; D011986:Receptors, Somatotropin / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism; D015854:Up-Regulation
D015853:Cysteine Proteinase Inhibitors; D008024:Ligands; D061965:Matrix Metalloproteinase Inhibitors; D009097:Multienzyme Complexes; D011480:Protease Inhibitors; D011986:Receptors, Somatotropin; D025801:Ubiquitin; D013006:Growth Hormone; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex