Nitric oxide sensitive-guanylyl cyclase subunit expression changes during estrous cycle in anterior pituitary glands

Abstract

Cabilla JP, Ronchetti SA, Nudler SI, Miler EA, Quinteros FA, Duvilanski BH. Nitric oxide sensitive-guanylyl cyclase subunit expression changes during estrous cycle in anterior pituitary glands. Am J Physiol Endocrinol Metab 296: E731-E737, 2009. First published January 13, 2009 doi:10.1152/ajpendo.90795.2008.-17␤-Estradiol (E 2 ) exerts inhibitory actions on the nitric oxide pathway in rat adult pituitary glands. Previously, we reported that in vivo E 2 acute treatment had opposite effects on soluble guanylyl cyclase (sGC) subunits, increasing ␣ 1-and decreasing ␤1-subunit protein and mRNA expression and decreasing sGC activity in immature rats. Here we studied the E 2 effect on sGC protein and mRNA expression in anterior pituitary gland from adult female rats to address whether the maturation of the hypothalamus-pituitary axis influences its effects and to corroborate whether these effects occur in physiological conditions such as during estrous cycle. E 2 administration causes the same effect on sGC as seen in immature rats, and these effects are estrogen receptor dependent. These results suggest that E 2 is the main effector of these changes. Since the sGC ␣-subunit increases while the sGC activity decreases, we studied if other less active isoforms of the sGC ␣-subunit are expressed. Here we show for the first time that sGC␣ 2 and sGC␣2 inhibitory (␣2i) isoforms are expressed in this gland, but only sGC␣ 2i mRNA increased after E2 acute treatment. Finally, to test whether E 2 effects take place under a physiological condition, sGC subunit expression was monitored over estrous cycle. sGC␣ 1, -␤1, and -␣ 2i fluctuate along estrous cycle, and these changes are directly related with E2 level fluctuations rather than to NO level variations. These findings show that E2 physiologically regulates sGC expression and highlight a novel mechanism by which E2 downregulates sGC activity in rat anterior pituitary gland. estrogen; soluble guanylyl cyclase; inhibitory subunit THE MAIN ESTROGENIC HORMONE 17␤-estradiol (E 2 ) plays important regulatory roles in a broad variety of biological processes, acting mainly on reproductive tissues, bone, liver, pituitary, and brain (9, 25).Nitric oxide (NO) is a signaling molecule that freely diffuses across cellular membranes where it binds to its main intracellular receptor, soluble guanylyl cyclase (sGC). This enzyme catalyzes the formation of cGMP from GTP. Subsequently, targets of cGMP such as cGMP-dependent protein kinases, cyclic nucleotide phosphodiesterases, and cyclic nucleotidesensitive ion channels are activated to continue the signal transduction (15,18).sGC is an heterodimeric enzyme and is comprised of two subunits, ␣ and ␤, of which four types exist (␣ 1 , ␣ 2, ␤ 1 , and ␤ 2 ). Both ␣-isoforms form a functional enzyme with the ␤ 1 -subunit, although the ␣ 1 ␤ 1 is the most abundant and widely expressed heterodimer, showing the greater activity (12, 13). The ␣ 2 is expressed in a more restricted pattern: in human tissues, it is present mainly in spleen, placenta, brain, ...

Nitric Oxide-Sensitive Guanylyl Cyclase Is Differentially Regulated by Nuclear and Non-Nuclear Estrogen Pathways in Anterior Pituitary Gland

“…As shown in Figures 3A and 4A and in agreement with previous report [6], free E2 increased α1 and decreased β1 mRNA and protein expression. Unexpectedly, at this time, EDC significantly decreased α1 mRNA and protein expression ( Figure 3A and 4A , respectively), an effect opposite to that seen after 3 h and 6 h of free E2 incubation ( Figure 2 ).…”

“…To investigate which kind of ER is involved in such effect, anterior pituitary cell cultures were incubated with membrane-impermeable E2 compounds: bovine serum albumin-conjugated E2 (E2-BSA) and estrogen dendrimer conjugate (EDC) [25] using the free steroid (E2) as control. First we studied the effect of E2-BSA on α1 and β1 mRNA levels after 6 h of treatment, the same time previously assayed [6]. Our results show that 1 nM E2-BSA was unable to reproduce 1 nM free E2 effects on sGC subunits mRNA expression at the same concentration ( Figure 1 ).…”

“…However, this treatment increases sGC α1 expression from both, immature and adult rats [5], [6]. The E2 effects on anterior pituitary sGC were observed not only after in vivo and in vitro treatment but also during estrous cycle.…”

Alternative splicing impairs soluble guanylyl cyclase function in aortic aneurysm

“…In addition to canonical full-length ␣1 (isoform A) and ␤1 (isoform 2) subunits, three more ␣1 protein isoforms (isoforms B, C, D) and five more ␤1 isoforms (isoforms 1, 3, 4, 5, 6) are predicted to be encoded by these transcripts. Our and other laboratories identified and characterized several sGC splice forms and demonstrated that their expression can modulate sGC function and enzymatic properties in vitro (4,5,7,8,43). These and other studies strongly suggested that alternative splicing of sGC transcripts may be important in regulation of sGC function in vivo.…”

Protein and mRNA expression of estradiol receptors during estrus in yaks (Bos grunniens)

“…The ER mRNA expression is high (Figure 1) in the hypothalamus during GnRH release. GnRH regulates the levels of LH and FSH in the anterior pituitary during estrus in the yak, and estradiol increases soluble guanylyl cyclase in the anterior pituitary at this time (Cabilla et al, 2009). The neuropeptide pituitary adenylate cyclase activating polypeptide is involved in estrus (Moore et al, 2005).…”