title: The short isoform of the ubiquitin ligase NEDD4L is a CREB target gene in hepatocytes.
abstract: During cycles of fasting and feeding, liver function is regulated by both transcriptional and post-translational events. Regulated protein degradation has recently emerged as a key mechanism to control abundance of specific hepatic proteins under different nutritional conditions. As glucagon signaling through cAMP and PKA is central to glucose output during fasting, we hypothesized that this signaling pathway may also regulate ubiquitin ligases in the fasted state. Here we show that fasting stimuli promote expression of the short isoform of the E3 ubiquitin ligase Nedd4l in primary mouse hepatocytes. Nedd4l-short mRNA and NEDD4L (short isoform) protein accumulate in glucagon-treated primary mouse hepatocytes and in liver tissues during fasting. We identified a functional cAMP response element in the alternate Nedd4l-short promoter; mutation of this element blunts cAMP-induced expression of a Nedd4l reporter construct. CREB occupies the endogenous Nedd4l locus near this element. CREB and its co-activator CRTC2, both activated by fasting stimuli, contribute to glucagon-stimulated Nedd4l-short expression in primary hepatocytes. siRNA-mediated Nedd4l depletion in primary hepatocytes did not affect gluconeogenic gene expression, glucose output or glycogen synthesis. Our findings reveal a new mechanism of Nedd4l transcriptional regulation in liver cells.
authors.affiliation: Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas, United States of America.
authors.forename: Jingqi
authors.initials: J
authors.lastname: Fu
authors.forename: Dmitry
authors.initials: D
authors.lastname: Akhmedov
authors.forename: Rebecca
authors.initials: R
authors.lastname: Berdeaux
mesh_terms: D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism*; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism*; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D000075702:Nedd4 Ubiquitin Protein Ligases; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D056827:Endosomal Sorting Complexes Required for Transport; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618485:Nedd4L protein, human; C000618461:Nedd4l protein, mouse; D044767:Ubiquitin-Protein Ligases