Somatic ‘Soluble’ Adenylyl Cyclase Isoforms Are Unaffected in Sacytm1Lex/Sacytm1Lex ‘Knockout’ Mice

BACKGROUND: Mammalian Soluble adenylyl cyclase (sAC, Adcy10, or Sacy) represents a source of the second messenger cAMP distinct from the widely studied, G protein-regulated transmembrane adenylyl cyclases. Genetic deletion of the second through fourth coding exons in Sacy(tm1Lex)/Sacy(tm1Lex) knockout mice results in a male sterile phenotype. The absence of any major somatic phenotype is inconsistent with the variety of somatic functions identified for sAC using pharmacological inhibitors and RNA interference. PRINCIPAL FINDINGS: We now use immunological and molecular biological methods to demonstrate that somatic tissues express a previously unknown isoform of sAC, which utilizes a unique start site, and which 'escapes' the design of the Sacy(tm1Lex) knockout allele. CONCLUSIONS/SIGNIFICANCE: These studies reveal increased complexity at the sAC locus, and they suggest that the known isoforms of sAC play a unique function in male germ cells

Water absorption and bicarbonate secretion in the intestine of the sea bream are regulated by transmembrane and soluble adenylyl cyclase stimulation

In the marine fish intestine luminal, HCO3 - can remove divalent ions (calcium and magnesium) by precipitation in the form of carbonate aggregates. The process of epithelial HCO3 - secretion is under endocrine control, therefore, in this study we aimed to characterize the involvement of transmembrane (tmACs) and soluble (sACs) adenylyl cyclases on the regulation of bicarbonate secretion (BCS) and water absorption in the intestine of the sea bream (Sparus aurata). We observed that all sections of sea bream intestine are able to secrete bicarbonate as measured by pH–Stat in Ussing chambers. In addition, gut sac preparations reveal net water absorption in all segments of the intestine, with significantly higher absorption rates in the anterior intestine that in the rectum. BCS and water absorption are positively correlated in all regions of the sea bream intestinal tract. Furthermore, stimulation of tmACs (10 lM FK? 500 lM IBMX) causes a significant decrease in BCS, bulk water absorption and short circuit current (Isc) in a region dependent manner. In turn, stimulation of sACs with elevated HCO3 - results in a significant increase in BCS, and bulk water absorption in the anterior intestine, an action completely reversed by the sAC inhibitor KH7 (200 lM). Overall, the results reveal a functional relationship between BCS and water absorption in marine fish intestine and modulation by tmACs and sAC. In light of the present observations, it is hypothesized that the endocrine effects on intestinal BCS and water absorption mediated by tmACs are locally and reciprocally modulated by the action of sACs in the fish enterocyte, thus fine-tuning the process of carbonate aggregate production in the intestinal lumen

Mitochondrial cAMP and Ca(2+) metabolism in adrenocortical cells.

The biological effects of physiological stimuli of adrenocortical glomerulosa cells are predominantly mediated by the Ca(2+) and the cAMP signal transduction pathways. The complex interplay between these signalling systems fine-tunes aldosterone secretion. In addition to the well-known cytosolic interactions, a novel intramitochondrial Ca(2+)-cAMP interplay has been recently recognised. The cytosolic Ca(2+) signal is rapidly transferred into the mitochondrial matrix where it activates Ca(2+)-sensitive dehydrogenases, thus enhancing the formation of NADPH, a cofactor of steroid synthesis. Quite a few cell types, including H295R adrenocortical cells, express the soluble adenylyl cyclase within the mitochondria and the elevation of mitochondrial [Ca(2+)] activates the enzyme, thus resulting in the Ca(2+)-dependent formation of cAMP within the mitochondrial matrix. On the other hand, mitochondrial cAMP (mt-cAMP) potentiates the transfer of cytosolic Ca(2+) into the mitochondrial matrix. This cAMP-mediated positive feedback control of mitochondrial Ca(2+) uptake may facilitate the rapid hormonal response to emergency situations since knockdown of soluble adenylyl cyclase attenuates aldosterone production whereas overexpression of the enzyme facilitates steroidogenesis in vitro. Moreover, the mitochondrial Ca(2+)-mt-cAMP-Ca(2+) uptake feedback loop is not a unique feature of adrenocortical cells; a similar signalling system has been described in HeLa cells as well