文档介绍：Growth Hormone & IGF Research 2000, Supplement B, $1-S8
Review article
Pulsatilityof .growth hormone (GH)
sagnalltng an laver cells: role of the
JAK-STAT5b pathway in GH action
H. K. Choi and D. J. Waxman
Division of Cell and Molecular Biology, Department of Biology, Boston University, Boston, Massachusetts, USA
Summary The intracellular signalling molecule and transcriptional activator STAT5b is a key mediator of the effects of
intermittent plasma growth hormone (GH) pulses on the male-specific pattern of liver gene expression and pubertal
body growth rates in rodents. Experiments with Stat5b gene-knockout mice have revealed that these GH-regulated,
male-specific phenotypes are a direct consequence of GH pulse-dependent STAT5b activation and that loss of function
of STAT5b cannot pensated for by the closely related signalling molecule STAT5a. Physiological plasma GH
pulses are required to obtain the high levels of activated STAT5b seen in the livers of males, and down-regulation of the
GH receptor (GHR)-JAK-STAT5b pathway in hepatocytes exposed to GH in a near-continuous fashion underlies the
low level of liver STAT5b activity that is characteristic of adult female rats. Termination of nuclear STAT5b signalling
occurs at the conclusion of a plasma GH pulse, with STAT5b deactivation catalysed by a tyrosine phosphatase. In
males, termination of th