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Soluble Adenylyl Cyclase Senses Alkalosis in Epithelial Base‐Secreting Cells
Author(s) -
Roa Jinae N,
Tresguerres Martin
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.760.23
Subject(s) - pendrin , extracellular , alkalosis , microbiology and biotechnology , intercalated cell , secretion , biology , adenylyl cyclase , biochemistry , chemistry , medicine , endocrinology , signal transduction , acidosis , transporter , gene
Regulation of acid/base (A/B) status (i.e. pH, CO 2 and [HCO 3 − ]) is essential for proper cell and organism functioning; however, the molecular mechanisms responsible for sensing A/B disturbances are largely unknown. Vertebrate animals have specialized epithelia such as kidneys and gills, which regulate blood A/B status therefore providing a stable extracellular environment for the rest of the cells. The mammalian nephron has several different intercalated cell (IC) types; some of them secrete acid and others base. However, due to their scarcity and the difficulty to work with them in isolation, little is know about the physiology of IC base‐secreting cells (β‐ICs). On the other hand, base‐secreting cells in elasmobranch gills are highly abundant and are functionally identical to β‐ICs: they express V‐H + ‐ATPase (VHA) and pendrin‐like anion exchangers that respectively translocate to basolateral and apical membranes to correct blood alkalosis. Also like β‐ICs, gill base‐secreting cells express the A/B sensor soluble adenylyl cyclase (sAC). In primary cultures of isolated gill cells, extracellular alkalosis triggered the translocation of VHA from the cytoplasm to the cell membrane, as previously reported in whole animal experiments. VHA translocation was dependent on sAC activity (as it was blocked by the specific inhibitor KH7), but not on transmembrane adenylyl cyclase activity (as it was insensitive to the P‐site inhibitor 2′5′dideoxyadenosine). This study demonstrates that sAC is a necessary and sufficient sensor of extracellular alkalosis in base‐secreting cells, and it highlights the power of comparative cellular physiology in future research on A/B sensing and regulation. Support or Funding Information JNR is supported by the William Townsend Porter Pre‐doctoral Fellowship from the American Physiological Society. MT is supported by NSF grant IOS 1354181 and Alfred P. Sloan Research Fellowship BR2013‐103 1VHA translocation in base‐secreting cells exposed to extracellular alkalosis. (a) Representative images of VHA localization in isolated gill cells, and (b) summary of ‘membrane VHA localization’ in cells exposed to control (n=59), NaCl (n=60), NaHCO 3 (n=56), NaHCO 3− + KH7 (n=60), and NaHCO 3− + 2,5‐DDA (n=60) treatments. NaHCO 3 significantly increased membrane VHA localization, which was inhibited by KH7 but not 2,5‐DDA (P<0.001). KH7 = sAC inhibitor. 2,5‐DDA = tmAC inhibitor.