Characterization of the human alpha 1beta 1 soluble guanylyl cyclase promoter: Key role for NF-kappa B(p50) and CCAAT-binding factors in regulating expression of the nitric oxide receptor

Soluble guanylyl cyclase (sGC) is the principal receptor for nitric oxide (NO) and plays a ubiquitous role in regulating cellular function. This is exemplified in the cardiovascular system where sGC governs smooth muscle tone and growth, vascular permeability, leukocyte flux and platelet aggregation. As a consequence, aberrant NO-sGC signalling has been linked to diseases including hypertension, atherosclerosis and stroke. Despite these key (patho)physiological roles, little is known about the expressional regulation of sGC. To address this deficit, we have characterised the promoter activity of human a1 and ss1 sGC genes in a cell-type relevant to cardiovascular (patho)physiology, primary human aortic smooth muscle cells. Luciferase reporter constructs revealed that the 0.3kb and 0.5kb regions upstream of the transcription start sites were optimal for a1 and ss1 sGC promoter activity, respectively. Deletion of consensus sites for c-Myb, GAGA, NFAT, NFB(p50) and CCAAT-binding factor(s) (CCAAT-BF) revealed that these are the principal transcription factors (TFs) regulating basal sGC expression. In addition, under pro-inflammatory conditions, the effects of the strongest a1 and ss1 sGC repressors were enhanced and enzyme expression and activity reduced; in particular, NFB(p50) is pivotal in regulating enzyme expression under such conditions. NO itself also elicited a cGMP-independent negative-feedback effect on sGC promoter activity that is mediated, in part, via CCAAT-BF activity. In sum, these data provide a systematic characterisation of the promoter activity of human sGC a1 and ss1 subunits and identify key TFs that govern subunit expression under basal and pro-inflammatory (i.e. atherogenic) conditions and in the presence of ligand NO.