title: Rasd1, a small G protein with a big role in the hypothalamic response to neuronal activation.
abstract: BACKGROUND
  Rasd1 is a member of the Ras family of monomeric G proteins that was first identified as a dexamethasone inducible gene in the pituitary corticotroph cell line AtT20. Using microarrays we previously identified increased Rasd1 mRNA expression in the rat supraoptic nucleus (SON) and paraventricular nucleus (PVN) of the hypothalamus in response to increased plasma osmolality provoked by fluid deprivation and salt loading. RASD1 has been shown to inhibit adenylyl cyclase activity in vitro resulting in the inhibition of the cAMP-PKA-CREB signaling pathway. Therefore, we tested the hypothesis that RASD1 may inhibit cAMP stimulated gene expression in the brain.
  
  
  RESULTS
  We show that Rasd1 is expressed in vasopressin neurons of the PVN and SON, within which mRNA levels are induced by hyperosmotic cues. Dexamethasone treatment of AtT20 cells decreased forskolin stimulation of c-Fos, Nr4a1 and phosphorylated CREB expression, effects that were mimicked by overexpression of Rasd1, and inhibited by knockdown of Rasd1. These effects were dependent upon isoprenylation, as both farnesyltransferase inhibitor FTI-277 and CAAX box deletion prevented Rasd1 inhibition of cAMP-induced gene expression. Injection of lentiviral vector into rat SON expressing Rasd1 diminished, whereas CAAX mutant increased, cAMP inducible genes in response to osmotic stress.
  
  
  CONCLUSIONS
  We have identified two mechanisms of Rasd1 induction in the hypothalamus, one by elevated glucocorticoids in response to stress, and one in response to increased plasma osmolality resulting from osmotic stress. We propose that the abundance of RASD1 in vasopressin expressing neurons, based on its inhibitory actions on CREB phosphorylation, is an important mechanism for controlling the transcriptional responses to stressors in both the PVN and SON. These effects likely occur through modulation of cAMP-PKA-CREB signaling pathway in the brain.
authors.affiliation: School of Clinical Sciences, University of Bristol, Bristol, BS1 3NY, UK. mike.greenwood@bristol.ac.uk.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Greenwood
authors.affiliation: School of Clinical Sciences, University of Bristol, Bristol, BS1 3NY, UK. mdymg@bristol.ac.uk.
authors.forename: Mingkwan
authors.initials: M
authors.lastname: Greenwood
authors.affiliation: School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil. mecawi.as@gmail.com.|Department of Physiology, University of Malaya, Kuala Lumpur, 50603, Malaysia. mecawi.as@gmail.com.|Department of Physiological Sciences, Biology Institute, Federal Rural University of Rio de Janeiro, Seropedica, Rio de Janeiro, Brazil. mecawi.as@gmail.com.
authors.forename: Andre S
authors.initials: AS
authors.lastname: Mecawi
authors.affiliation: School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil. jantunesr@gmail.com.
authors.forename: José
authors.initials: J
authors.lastname: Antunes-Rodrigues
authors.affiliation: School of Physiology and Pharmacology, University of Bristol, Bristol, BS8 1TD, UK. Julian.F.R.Paton@bristol.ac.uk.
authors.forename: Julian F R
authors.initials: JF
authors.lastname: Paton
authors.affiliation: School of Clinical Sciences, University of Bristol, Bristol, BS1 3NY, UK. d.murphy@bristol.ac.uk.|Department of Physiology, University of Malaya, Kuala Lumpur, 50603, Malaysia. d.murphy@bristol.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Murphy
mesh_terms: D000818:Animals; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D016086:Lentivirus / Q000378:metabolism; D008297:Male; D051379:Mice; D008954:Models, Biological; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009997:Osmotic Pressure / Q000187:drug effects; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010904:Pituitary Gland, Posterior / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D012149:Restraint, Physical; D013312:Stress, Physiological / Q000187:drug effects; D013495:Supraoptic Nucleus / Q000187:drug effects / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D005938:Glucocorticoids; D012333:RNA, Messenger; C528215:Rasd1 protein, rat; D014157:Transcription Factors; D003907:Dexamethasone; D000242:Cyclic AMP; C498511:Rasd1 protein, mouse; D018631:ras Proteins