Nescient helix-loop-helix 2 interacts with signal transducer and activator of transcription 3 to regulate transcription of prohormone convertase 1/3.
Mechanisms controlling body weight involve gene regulation through the activation of signal transduction pathways. The Janus kinase/signal transducer and activator of transcription (STAT) signal transduction pathway is the mechanism primarily used by leptin in the hypothalamus. The transcription factor nescient helix-loop-helix 2 (Nhlh2) is a downstream target of leptin signaling and is expressed in proopiomelanocortin arcuate neurons. Proopiomelanocortin is cleaved by prohormone convertase 1/3 (PC1/3) to produce peptides that regulate the body's response to energy availability. Previous studies show that the PC1/3 promoter contains STAT3 sites mediating leptin-induced PC1/3 expression, and that Nhlh2 is required for hypothalamic PC1/3 expression because Nhlh2 knockout mice have reduced PC1/3 mRNA levels. Studies herein reveal that leptin-induced PC1/3 gene expression is abrogated in N2KO mice, and that in a hypothalamic cell line both STAT3 and Nhlh2 are required for the full transcriptional response of a PC1/3 reporter gene after leptin stimulation. Furthermore, it is shown that Nhlh2 binds to E-box motifs found adjacent to STAT3 sites in the PC1/3 promoter both in vitro and in chromatin immunoprecipitation assays. Finally, two different protein-protein interaction assays confirm the presence of a STAT3:Nhlh2 heterodimer on the PC1/3 promoter. The Nhlh2:STAT3 heterodimer may be an important transcriptional regulator of other hypothalamic genes in the leptin signaling pathway. These data confirm Nhlh2 as an integral element of the Janus kinase/STAT signaling pathway and are the first to demonstrate coordinated control of PC1/3 transcription by Nhlh2 and STAT3 after leptin stimulation.
Fox
Dana L
DL
Department of Veterinary, University of Massachusets, Amherst, Massachusets 01002, USA.
Good
Deborah J
DJ
D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D019281:Dimerization; D024721:E-Box Elements; D004734:Energy Metabolism / Q000187:drug effects / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D020738:Leptin / Q000494:pharmacology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000187:drug effects; D045664:Proprotein Convertase 1 / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
D051792:Basic Helix-Loop-Helix Proteins; D020738:Leptin; D045664:Proprotein Convertase 1; D050796:STAT3 Transcription Factor; C484104:Nhlh2 protein, mouse; C494087:Stat3 protein, mouse