Regulators of G-protein signaling 4 in adrenal gland: localization, regulation, and role in aldosterone secretion.
Regulators of G-protein signaling (RGS proteins) interact with Galpha subunits of heterotrimeric G-proteins, accelerating the rate of GTP hydrolysis and finalizing the intracellular signaling triggered by the G-protein-coupled receptor (GPCR)-ligand interaction. Angiotensin II (Ang II) interacts with its GPCR in adrenal zona glomerulosa cells and triggers a cascade of intracellular signals that regulates steroidogenesis and proliferation. On screening for adrenal zona glomerulosa-specific genes, we found that RGS4 was exclusively localized in the zona glomerulosa of the rat adrenal cortex. We studied RGS4 expression and regulation in the rat adrenal gland, including the signaling pathways involved, as well as the role of RGS4 in steroidogenesis in human adrenocortical H295R cells. We reported that RGS4 mRNA expression in the rat adrenal gland was restricted to the adrenal zonal glomerulosa and upregulated by low-salt diet and Ang II infusion in rat adrenal glands in vivo. In H295R cells, Ang II caused a rapid and transient increase in RGS4 mRNA levels mediated by the calcium/calmodulin/calmodulin-dependent protein kinase and protein kinase C pathways. RGS4 overexpression by retroviral infection in H295R cells decreased Ang II-stimulated aldosterone secretion. In reporter assays, RGS4 decreased Ang II-mediated aldosterone synthase upregulation. In summary, RGS4 is an adrenal gland zona glomerulosa-specific gene that is upregulated by aldosterone secretagogues, in vivo and in vitro, and functions as a negative feedback of Ang II-triggered intracellular signaling. Alterations in RGS4 expression levels or functions may be involved in deregulations of Ang II signaling and abnormal aldosterone secretion.
Romero
Damian G
DG
Division of Endocrinology, G V (Sonny) Montgomery VA Medical Center, and Department of Medicine, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216, USA. dromero@medicine.umsmed.edu
Zhou
Ming Yi
MY
Yanes
Licy L
LL
Plonczynski
Maria W
MW
Washington
Tanganika R
TR
Gomez-Sanchez
Celso E
CE
Gomez-Sanchez
Elise P
EP
D000293:Adolescent; D000328:Adult; D000450:Aldosterone / Q000378:metabolism*; D000804:Angiotensin II / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D004039:Diet, Sodium-Restricted; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism; D005822:Genetic Vectors / Q000008:administration & dosage; D006801:Humans; D008297:Male; D008875:Middle Aged; D011493:Protein Kinase C / Q000378:metabolism; D020710:RGS Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012190:Retroviridae / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D014161:Transduction, Genetic; D015854:Up-Regulation; D015384:Zona Glomerulosa / Q000737:chemistry* / Q000378:metabolism
D020710:RGS Proteins; D012333:RNA, Messenger; D000804:Angiotensin II; C098799:RGS4 protein; D000450:Aldosterone; D011493:Protein Kinase C; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019204:GTP-Binding Proteins