Selective stimulation of G-6-Pase catalytic subunit but not G-6-P transporter gene expression by glucagon in vivo and cAMP in situ

• Published in: American journal of physiology: endocrinology and metabolism Vol. 286; no. 5; pp. E795 - E808
• Main Authors: Hornbuckle, Lauri A, Everett, Carrie A, Martin, Cyrus C, Gustavson, Stephanie S, Svitek, Christina A, Oeser, James K, Neal, Doss W, Cherrington, Alan D, O'Brien, Richard M
• Format: Journal Article
• Language: English
• Published: United States 01.05.2004
• Subjects: Animals; Antiporters; Catalytic Domain - genetics; Catalytic Domain - physiology; Cells, Cultured; Cyclic AMP - physiology; Dogs; Fatty Acids, Nonesterified - physiology; Female; Gene Expression Regulation; Glucagon - physiology; Glucose Clamp Technique; Glucose-6-Phosphatase - genetics; Glucose-6-Phosphatase - metabolism; Glycerol - metabolism; Hepatocytes - metabolism; Insulin - physiology; Liver - metabolism; Male; Monosaccharide Transport Proteins; Phosphotransferases - genetics; Phosphotransferases - metabolism; RNA, Messenger - analysis; Second Messenger Systems - physiology
• ISSN: 0193-1849; 1522-1555
• DOI: 10.1152/ajpendo.00455.2003

Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, Tennessee 37232 Submitted 9 October 2003 ; accepted in final form 6 January 2004 We recently compared the regulation of glucose-6-phosphatase (G-6-Pase) catalytic subunit and glucose 6-phosphate (G-6- P ) transporter gene expression by insulin in conscious dogs in vivo (Hornbuckle LA, Edgerton DS, Ayala JE, Svitek CA, Neal DW, Cardin S, Cherrington AD, and O'Brien RM. Am J Physiol Endocrinol Metab 281: E713–E725, 2001). In pancreatic-clamped, euglycemic conscious dogs, a 5-h period of hypoinsulinemia led to a marked increase in hepatic G-6-Pase catalytic subunit mRNA; however, G-6- P transporter mRNA was unchanged. Here, we demonstrate, again using pancreatic-clamped, conscious dogs, that glucagon is a candidate for the factor responsible for this selective induction. Thus glucagon stimulated G-6-Pase catalytic subunit but not G-6- P transporter gene expression in vivo. Furthermore, cAMP stimulated endogenous G-6-Pase catalytic subunit gene expression in HepG2 cells but had no effect on G-6- P transporter gene expression. The cAMP response element (CRE) that mediates this induction was identified through transient transfection of HepG2 cells with G-6-Pase catalytic subunit-chloramphenicol acetyltransferase fusion genes. Gel retardation assays demonstrate that this CRE binds several transcription factors including CRE-binding protein and CCAAT enhancer-binding protein. insulin; fatty acids; gene transcription; cyclic adenosine monophosphate; glucose-6-phosphatase; glucose 6-phosphate Address for reprint requests and other correspondence: R. M. O'Brien, Dept. of Molecular Physiology and Biophysics, 761 PRB, Vanderbilt Univ. Medical School, Nashville, TN 37232–0615 (E-mail: richard.obrien{at}mcmail.vanderbilt.edu ).