Cell-type-specific function of the C-type natriuretic peptide gene promoter in rat anterior pituitary-derived cultured cell lines.

Abstract

The promoter function of the human C-type natriuretic peptide (CNP) (23,38), and then was identified in rat and human brains (19,28). CNP shares considerable sequence homology with ANP and BNP, especially within the 17-residue ring portion formed by a disulfide bond between two cysteine residues. According to the cloned cDNA and genes for CNP from various species (17,19,28,40,41), the structure of CNP is highly conserved among species, and rat, porcine, and human CNP-22 are actually identical. CNP seems to exert pharmacological actions similar to those of ANP and BNP, including natriuretic, diuretic, and vasorelaxant effects (40), albeit with lesser potency. Although the vasorelaxant activity of CNP in the isolated rat aorta is 16-fold lower than that of ANP, CNP is a more effective stimulator of cyclic GMP generation in cultured vascular smooth muscle cells (8) and may be a more potent growth inhibitor of these cells than ANP is (9). While ANP and BNP are mainly cardiac hormones (27), CNP is localized in the brain and very little is detected in other peripheral tissues, including the heart (19, 28, 42). A receptor specific for CNP has been designated the ANP-B (or GC-B) receptor (18) and has been shown to exist in the brain and pituitary gland (20, 43). Therefore, it is possible that CNP functions in a manner distinct from ANP and BNP, as a neuromodulator, for example. As a matter of fact, CNP is suggested to have some actions on the rat central nervous system (12,13,31

Regulation of C-type natriuretic peptide expression

“…This last observation is particularly interesting in light of the reported mouse vs. human differences in CNP response to LPS since the bacterial protein is known to signal through the NF-␤ pathway [95]. In addition, although both species possess at least one GC box in the promoter, the human CNP promoter possesses two GC boxes in tandem to constitute the 'GC-rich' DNA-binding site as described above [62]. This could represent a crucial difference in CNP transcriptional regulation between rodent and human.…”

“…The consensus sequence for Ap-2 was similarly without effect. Furthermore, a 70 kD putative regulatory protein, identified by its binding to the GC-rich region, did not match the MWs for either Sp-1, CREB or Ap-2 [62]. On the contrary, Thompson et al [88] have very recently shown evidence using electrophoretic mobility shift assays (EMSA) that both Sp-1 and Sp-3 bind as a complex to the putative GC-rich regulatory site in the proximal Nppc promoter.…”

“…Ohta et al [62] found, however, that neither the Sp-1 nor the CREB consensus binding sequence was able to compete effectively with the GC-rich region of human Nppc for binding of nuclear protein. The consensus sequence for Ap-2 was similarly without effect.…”

“…A third peptide, NTpro-CNP, derived from the N-terminal of the pre-pro peptide has no known function, but circulating at higher levels than either CNP-22 or CNP-53, it serves as a convenient serum marker of changes in active CNP in response to endocrine alterations and disease [12,25,65]. The proximal 5 -flanking region of the gene was found to contain two GC-boxes (Sp-1 binding sites) in tandem in addition to several other cis elements including an inverted CCAAT box (Y box), and a CRE-like (cAMP response-like) element within 50 bp upstream of a Tata box (TATAAA) [62,63,90]. These sequences have been hypothesized to constitute potential targets in the regulation of CNP expression, and are not present in the promoter regions of either the ANP or BNP genes [87].…”

“…A detailed functional analysis of the proximal promoter region in the human CNP gene [62] extending to approximately 1400 bp upstream of the transcription start site, demonstrated the existence of a positive regulatory region between positions −54 and −19, a sequence encompassing the tandem GC-boxes. In addition, at least two negative regulatory regions were identified much further upstream.…”