Role of transforming growth factor (TGF)-beta Type I and TGF-beta type II receptors in the TGF-beta1-regulated gene expression in pituitary prolactin-secreting lactotropes.
Transforming growth factor beta1 (TGF-beta1) inhibits pituitary lactotrope proliferation and secretion of PRL in an autocrine/paracrine manner. In this study, the role of TGF-beta1 type I (TbetaR-I) and TGF-beta type II (TbetaR-II) receptors in TGF-beta1-regulated gene expression in lactotropes was determined using anterior pituitary cells known to be responsive to TGF-beta1 growth inhibition and using a transformed PR1 cell line known to be nonresponsive to TGF-beta1 growth inhibition. Treatment with TGF-beta1 inhibited cell proliferation and decreased PRL mRNA levels in anterior pituitary cells, but in PR-1 cells, the treatment caused only decreased PRL mRNA levels. Affinity labeling of TGF-beta binding proteins indicated that anterior pituitary cells contain several TGF-beta-binding protein complexes, including the 65 kDa size TbetaR-I and 95 kDa size TbetaR-II. In the PR1 cells, the major complex found was similar to the 65 kDa size of TbetaR-I. Immunocytochemistry identified TbetaR-I and TbetaR-II receptor proteins in lactotropes but detected primarily TbetaR-I receptor protein in PR1 cells. RT-PCR detection of TbetaR-I and TbetaR-II mRNA identified both receptor mRNA transcripts in anterior pituitary cells and in PR1 cells but the levels of TbetaR-II and TbetaR-I mRNA transcripts in PR1 cells was much lower than that in anterior pituitary cells. Determination of the TGF-beta1 gene responses in PR1 cells following TbetaR-I and TbetaR-II gene transfection indicated that PR1 cells transactivate transcription of the TGF-beta-responsive p3TP-Lux reporter in the absence of cotransfected TbetaR-II receptor. The introduction of the TbetaR-II receptor alone or in combination with TbetaR-I confer ligand-independent reporter transactivation in these cells. When only TbetaR-I was introduced along with reporter, a ligand-dependent transactivation was observed. These data suggest for the first time that the TGF-beta1-mediated transcriptional activation response can be distinguished from the growth response in lactotropes. Furthermore, the TGF-beta1 gene-transcription response is less dependent on TbetaR-II receptor expression than is the TGF-beta1 growth-inhibitory response.
Sarkar
D K
DK
Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, Center for Reproductive Biology, Washington State University, Pullman 99164-6520, USA. sarkar@vetmed.wsu.edu
Pastorcic
M
M
De
A
A
Engel
M
M
Moses
H
H
Ghasemzadeh
M B
MB
D030201:Activin Receptors, Type I; D000818:Animals; D002455:Cell Division; D002478:Cells, Cultured; D005260:Female; D005786:Gene Expression Regulation; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D011388:Prolactin / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000502:physiology*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D012333:RNA, Messenger; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D011388:Prolactin; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; C000625843:Tgfbr1 protein, rat