HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Clayton, P E Articles by Thorner, M O Search for Related Content PubMed PubMed Citation Articles by Clayton, P E Articles by Thorner, M O

GH induces hepatic IGF-I synthesis by increasing transcription of its gene. IGF-I is synthesized, however, in many other tissues where the effect of GH on its gene expression is less well characterized. IGF-I and GH are produced by human lymphocytes and may function as autocrine regulators of lymphoproliferation. We have therefore used the human IM9 lymphocyte cell line to (A) define the IGF-I gene transcripts expressed and (B) investigate the effect of GH on early (protein tyrosine phosphorylation) and late (changes in IGF-I mRNA levels) events in intracellular signal transduction. Multiple IGF-I mRNA species, ranging in size from 0·9 to 5·8 kb, were detected by Northern hybridization of poly(A)⁺ mRNA from IM9 cells. The human IGF-I gene contains at least six exons and alternative splicing produces a number of transcripts. Solution hybridization with exon-specific riboprobes and amplification by PCR using exon-specific primers revealed that multiple transcripts were expressed in IM9 cells, and that exon 2 was the dominant leader exon.

Treatment of IM9 cells with 200 ng recombinant human (rh)GH/ml led to the specific tyrosine phosphorylation of three intracellular proteins (93, 120 and 134 kDa), which are involved in the initial signalling of the GH transduction pathway. However a solution hybridization assay using the IGF-IA specific riboprobe on IM9 cell RNA from similar experiments revealed that GH treatment did not change IGF-I gene expression.

This study has demonstrated (A) that the IGF-I gene is expressed in human IM9 lymphocytes, (B) that in contrast to other human tissue, exon 2 is the major leader exon, and (C) that rhGH induces tyrosine phosphorylation of 93, 120 and 134 kDa proteins but does not alter IGF-I gene expression. The IM9 cell may form an important model to investigate a GH transduction pathway not coupled to the IGF-I gene.

This article has been cited by other articles:

				C. A. BLOOR, R. A. KNIGHT, R. K. KEDIA, M. A. SPITERI, and J. T. ALLEN Differential mRNA Expression of Insulin-like Growth Factor-1 Splice Variants in Patients With Idiopathic Pulmonary Fibrosis and Pulmonary Sarcoidosis Am. J. Respir. Crit. Care Med., July 15, 2001; 164(2): 265 - 272. [Abstract] [Full Text] [PDF]

				R. Clark The Somatogenic Hormones and Insulin-Like Growth Factor-1: Stimulators of Lymphopoiesis and Immune Function Endocr. Rev., April 1, 1997; 18(2): 157 - 179. [Abstract] [Full Text]

				Z. S. Gucev, Y. Oh, K. M. Kelley, J. I. Labarta, P. Vorwerk, and R. G. Rosenfeld Evidence for Insulin-Like Growth Factor (IGF)-Independent Transcriptional Regulation of IGF Binding Protein-3 by Growth Hormone in SKHEP-1 Human Hepatocarcinoma Cells Endocrinology, April 1, 1997; 138(4): 1464 - 1470. [Abstract] [Full Text] [PDF]