Suppressor of cytokine signalling (SOCS) proteins act as part of a classica
l negative feedback loop regulating cytokine signal transduction. Expressio
n of SOCS proteins is induced in response to cytokines and down-regulates t
he cytokine signal by inhibiting the JAK/STAT pathway. Growth hormone (GH)
was previously shown to induce strong transient expression of SOCS-3 and to
a lesser extent CIS, SOCS-1 and SOCS-2 in mouse liver (Adams, T.E., Hansen
, J.A., Starr, R., Nicola, N.A., Hilton, D.J., Billestrup, N., 1998. Growth
hormone preferentially induces the rapid, transient expression of SOCS-3,
a novel inhibitor of,cytokine receptor signalling. J. Biol. Chem. 273, 1285
-1287.). In this work we have compared GH-induced SOCS gene expression in w
ild-type and STAT5b-deficient mice, and show that: STAT5b is required for t
he induction of SOCS-2 and SOCS-3 in liver. In contrast, the absence of STA
T5b has no effect on the GH-induced expression of CIS and SOCS-2 mRNA in th
e mammary gland. Suprisingly, there is no activation of SOCS-3 expression i
n mammary glands of wild-type and STAT5b mutant mice following GH administr
ation. These results highlight both tissue- and factor-specific differences
in the regulation of SOCS gene expression by STAT5a/b. (C) 1999 Elsevier S
cience Ireland Ltd. All rights reserved.