Activation by thyroid stimulating hormone of nerve growth factor-induced gene-B expression in thyrocytes in culture: relation with proliferation and specific gene expression.
Nerve growth factor-induced gene-B (NGFI-B) is an immediate early gene first found as a part of the PC12 cell response to NGF (Milbrandt, J., Science 238 (1987) 797-799). We have previously reported that NGFI-B mRNA is strongly upregulated by thyroid-stimulating hormone (TSH) in dog thyrocytes in culture (Pichon et al., Endocrinology 137 (1996) 4691-4698). In this study, we have analyzed the regulation of NGFI-B mRNA expression by a variety of agents acting on thyrocytes proliferation and/or differentiation. We show that: (1) the induction of NGFI-B mRNA is stronger after stimulation of the cAMP cascade, but it is not restricted to this signaling pathway; (2) the powerful mitogens for thyroid cells EGF and HGF have little or no effect on NGFI-B mRNA induction; (3) NGFI-B mRNA is induced by anisomycin at a subinhibitory concentration for protein synthesis, and is superinduced by the combination of TSH and anisomycin; this treatment decreases the TSH-induced proliferation levels, but does not inhibit the induction of some differentiation markers; and (4) both in dog and in pig thyrocytes, NGFI-B mRNA induction is observed after a variety of treatments stimulating differentiation, but without proliferative effects. Our results therefore suggest that NGFI-B mRNA induction might not be related to TSH-induced thyrocyte proliferation, but could participate in the differentiation program triggered by TSH.
Institut de Recherche Interdisciplinaire en Biologie Humaine et Nucléaire, Faculté de Médecine, Université Libre de Bruxelles, Brussels, Belgium.
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Jiménez-Cervantes
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Pichon
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Dumont
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Maenhaut
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D004285:Dogs; D005786:Gene Expression Regulation; D007328:Insulin / Q000172:deficiency; D008934:Mitogens / Q000494:pharmacology; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D013552:Swine; D013961:Thyroid Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology / Q000502:physiology*; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics
D004268:DNA-Binding Proteins; D007328:Insulin; D008934:Mitogens; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D014157:Transcription Factors; D013972:Thyrotropin