Transcription factor CREB3L1 mediates cAMP and glucocorticoid regulation of arginine vasopressin gene transcription in the rat hypothalamus.
BACKGROUND
Arginine vasopressin (AVP), a neuropeptide hormone that functions in the regulation of water homeostasis by controlling water re-absorption at kidneys, is synthesised in supraoptic nucleus and paraventricular nucleus of the hypothalamus. An increase in plasma osmolality stimulates secretion of AVP to blood circulation and induces AVP synthesis in these nuclei. Although studies on mechanism of AVP transcriptional regulation in hypothalamus proposed that cAMP and glucocorticoids positively and negatively regulate Avp expression, respectively, the molecular mechanisms have remained elusive. Recently, we identified CREB3L1 (cAMP-responsive element binding protein 3 like 1) as a putative transcription factor of Avp transcription in the rat hypothalamus. However the mechanism of how CREB3L1 is regulated in response of hyperosmotic stress in the neurons of hypothalamus has never been reported. This study aims to investigate effect of previously reported regulators (cAMP and glucocorticoid) of Avp transcription on transcription factor CREB3L1 in order to establish a molecular explanation for cAMP and glucocorticoids effect on AVP expression.


RESULTS
The effect of cAMP and glucocorticoid treatment on Creb3l1 was investigated in both AtT20 cells and hypothalamic organotypic cultures. The expression of Creb3l1 was increased in both mRNA and protein level by treatment with forskolin, which raises intracellular cAMP levels. Activation of cAMP by forskolin also increased Avp promoter activity in AtT20 cells and this effect was blunted by shRNA mediated silencing of Creb3l1. The forskolin induced increase in Creb3l1 expression was diminished by combined treatment with dexamethasone, and, in vivo, intraperitoneal dexamethasone injection blunted the increase in Creb3l1 and Avp expression induced by hyperosmotic stress.


CONCLUSIONS
Here we shows that cAMP and glucocorticoid positively and negatively regulate Creb3l1 expression in the rat hypothalamus, respectively, and regulation of cAMP on AVP expression is mediated through CREB3L1. This data provides the connection between CREB3L1, a newly identified transcription factor of AVP expression, with the previously proposed mechanism of Avp transcription which extends our understanding in transcription regulation of Avp in the hypothalamus.
School of Clinical Sciences, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol, BS1 3NY, England. mingkwan.greenwood@bristol.ac.uk.
Mingkwan
M
Greenwood
School of Clinical Sciences, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol, BS1 3NY, England. mike.greenwood@bristol.ac.uk.
Michael P
MP
Greenwood
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.
Andre S
AS
Mecawi
Department of Physiology, University of Malaya, Kuala Lumpur, 50603, Malaysia. suyi91189@hotmail.com.
Su Yi
SY
Loh
School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil. jantunesr@gmail.com.
José Antunes
JA
Rodrigues
School of Physiology and Pharmacology, University of Bristol, Bristol, BS8 1TD, England. Julian.F.R.Paton@bristol.ac.uk.
Julian F R
JF
Paton
School of Clinical Sciences, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol, BS1 3NY, England. d.murphy@bristol.ac.uk.|Department of Physiology, University of Malaya, Kuala Lumpur, 50603, Malaysia. d.murphy@bristol.ac.uk.
David
D
Murphy
D000818:Animals; D001127:Arginine Vasopressin / Q000235:genetics* / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D005938:Glucocorticoids / Q000494:pharmacology*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009924:Organ Culture Techniques; D009997:Osmotic Pressure / Q000187:drug effects; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017207:Rats, Sprague-Dawley; D013312:Stress, Physiological / Q000187:drug effects; D013495:Supraoptic Nucleus / Q000187:drug effects / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects*
C552423:CREB3L1 protein, rat; D017362:Cyclic AMP Response Element-Binding Protein; D005938:Glucocorticoids; D001127:Arginine Vasopressin; D005576:Colforsin; D003907:Dexamethasone; D000242:Cyclic AMP