TY - JOUR
T1 - Regulation of glucose transport and c-fos and egr-1 expression in cells with mutated or endogenous growth hormone receptors
AU - Gong, T W
AU - Meyer, D J
AU - Liao, J
AU - Hodge, C L
AU - Campbell, G S
AU - Wang, X
AU - Billestrup, Nils
AU - Carter-Su, C
AU - Schwartz, J
PY - 1998/4
Y1 - 1998/4
N2 - To identify mechanisms by which GH receptors (GHR) mediate downstream events representative of growth and metabolic responses to GH, stimulation by GH of c-fos and egr-1 expression and glucose transport activity were examined in Chinese hamster ovary (CHO) cells expressing mutated GHR. In CHO cells expressing wild-type GHR(GHR(1-638)), GH stimulated the expression of c-fos and egr-1, and stimulated 2-deoxyglucose uptake, responses also mediated by endogenous GHR in 3T3-F442A cells. Deletion of the proline-rich box 1 of GHR (GHR(deltaP)) abrogated all of these responses to GH, indicating that box 1, a site of association of GHR with the tyrosine kinase JAK2, is crucial for these GH-stimulated responses. As the C-terminal half of the cytoplasmic domain of GHR is required for GH-stimulated calcium flux and for stimulation of spi-2.1 transcription, GHR lacking this sequence (GHR(1-454)) were examined. Not only did GHR(1-454) mediate stimulation of c-fos and egr-1 expression and 2-deoxyglucose uptake, but they also mediated GH-stimulated transcriptional activation via Elk-1, a transcription factor associated with the c-fos Serum Response Element. Thus, the C-terminal half of the cytoplasmic domain of GHR is not required for GH-stimulated c-fos transcription, suggesting that increased calcium is not required for GH-stimulated c-fos expression. In CHO cells lacking all but five N-terminal residues of the cytoplasmic domain (GHR(1-294)), GH did not induce c-fos or egr-1 expression or stimulate 2-deoxyglucose uptake. Further, in 3T3-F442A fibroblasts with endogenous GHR, GH-stimulated c-fos expression and 2-deoxyglucose uptake were reduced by the tyrosine kinase inhibitors herbimycin A, staurosporine, and P11. Herbimycin A and staurosporine inhibit JAK2 and tyrosyl phosphorylation of all proteins stimulated by GH, whereas P11 inhibits the GH-dependent tyrosyl phosphorylation of only some proteins, including extracellular signal regulated kinases ERK1 and -2, but not JAK2. Taken together, these results implicate association of GHR with JAK2 and GH-stimulated tyrosyl phosphorylation of an additional cellular protein in GH-stimulated glucose transport and c-fos and egr-1 expression. These studies also indicate that, in contrast to spi-2.1, the N-terminal half of the cytoplasmic domain of GHR is sufficient to mediate stimulation of c-fos and egr-1 expression and Elk-1 activation, supporting multiple mechanisms for GH signaling to the nucleus.
AB - To identify mechanisms by which GH receptors (GHR) mediate downstream events representative of growth and metabolic responses to GH, stimulation by GH of c-fos and egr-1 expression and glucose transport activity were examined in Chinese hamster ovary (CHO) cells expressing mutated GHR. In CHO cells expressing wild-type GHR(GHR(1-638)), GH stimulated the expression of c-fos and egr-1, and stimulated 2-deoxyglucose uptake, responses also mediated by endogenous GHR in 3T3-F442A cells. Deletion of the proline-rich box 1 of GHR (GHR(deltaP)) abrogated all of these responses to GH, indicating that box 1, a site of association of GHR with the tyrosine kinase JAK2, is crucial for these GH-stimulated responses. As the C-terminal half of the cytoplasmic domain of GHR is required for GH-stimulated calcium flux and for stimulation of spi-2.1 transcription, GHR lacking this sequence (GHR(1-454)) were examined. Not only did GHR(1-454) mediate stimulation of c-fos and egr-1 expression and 2-deoxyglucose uptake, but they also mediated GH-stimulated transcriptional activation via Elk-1, a transcription factor associated with the c-fos Serum Response Element. Thus, the C-terminal half of the cytoplasmic domain of GHR is not required for GH-stimulated c-fos transcription, suggesting that increased calcium is not required for GH-stimulated c-fos expression. In CHO cells lacking all but five N-terminal residues of the cytoplasmic domain (GHR(1-294)), GH did not induce c-fos or egr-1 expression or stimulate 2-deoxyglucose uptake. Further, in 3T3-F442A fibroblasts with endogenous GHR, GH-stimulated c-fos expression and 2-deoxyglucose uptake were reduced by the tyrosine kinase inhibitors herbimycin A, staurosporine, and P11. Herbimycin A and staurosporine inhibit JAK2 and tyrosyl phosphorylation of all proteins stimulated by GH, whereas P11 inhibits the GH-dependent tyrosyl phosphorylation of only some proteins, including extracellular signal regulated kinases ERK1 and -2, but not JAK2. Taken together, these results implicate association of GHR with JAK2 and GH-stimulated tyrosyl phosphorylation of an additional cellular protein in GH-stimulated glucose transport and c-fos and egr-1 expression. These studies also indicate that, in contrast to spi-2.1, the N-terminal half of the cytoplasmic domain of GHR is sufficient to mediate stimulation of c-fos and egr-1 expression and Elk-1 activation, supporting multiple mechanisms for GH signaling to the nucleus.
KW - 3T3 Cells
KW - Animals
KW - Biological Transport
KW - CHO Cells
KW - Cricetinae
KW - DNA-Binding Proteins
KW - Deoxyglucose
KW - Early Growth Response Protein 1
KW - Enzyme Inhibitors
KW - Gene Deletion
KW - Gene Expression Regulation
KW - Genes, fos
KW - Growth Hormone
KW - Immediate-Early Proteins
KW - Mice
KW - Mutagenesis
KW - Protein-Tyrosine Kinases
KW - Rats
KW - Receptors, Somatotropin
KW - Recombinant Proteins
KW - Transcription Factors
U2 - 10.1210/endo.139.4.5893
DO - 10.1210/endo.139.4.5893
M3 - Journal article
C2 - 9528972
SN - 0013-7227
VL - 139
SP - 1863
EP - 1871
JO - Journal of Clinical Endocrinology and Metabolism
JF - Journal of Clinical Endocrinology and Metabolism
IS - 4
ER -