Binding and signalling properties of a growth hormone enhancing monoclonal antibody

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• 作者：James Beattie ; Silvia Bramani ; Camillo Secchi and James Mockridge
• 关键词：tyrosine phosphorylation ; adipocytes ; growth hormone
• 刊名：Molecular and Cellular Biochemistry
• 出版年：1999
• 出版时间：1999
• 年：1999
• 卷：198
• 期：1/2
• 页码：61-67
• 全文大小：121 KB

文摘

We have used a sequential, qualitative biosensor based assay to demonstrate that OA15, a monoclonal antibody which enhances in vivo the activity of bovine growth hormone (bGH) does not disrupt the interaction between bGH and its cognate receptor (as represented by recombinant bovine GH binding protein -rbGHBP). We have confirmed this using a classical cell-based radio-receptor assay with the GH-responsive mouse pre-adipocyte cell line 3T3-F442A. The fact that OA15 binding to bGH still allows hormone to interact with its receptor, allows us to test the hypothesis that there is any amplification of signalling events following hormone-MAb treatment of 3T3-F442A cells. We have used as a reporter of GH activity the rapid stimulation of JAK-2 tyrosine phosphorylation which is a critical first step in GH signalling events. We demonstrate that binding of rbGH by OA15 attenuates hormone stimulation of JAK-2 tyrosine phosphorylation. We conclude that although OA15 does not disrupt GH-GH receptor (GHR) interactions it does interfere with subsequent GH activity at the molecular and cellular level. We further speculate therefore that the biological enhancing activity of this antibody is most likely due to an in vivo effect as presentation of antibody-hormone complexes to a GH-target cell inhibits hormone activity.