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Endogenous surface expression of ΔF508‐CFTR mediates cAMP‐stimulated Cl − current in CFTR ΔF508/ΔF508 pig thyroid epithelial cells
Author(s) -
Li Yonghai,
Ganta Suhasini,
Fong Peying
Publication year - 2012
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.2011.060756
Subject(s) - δf508 , cystic fibrosis transmembrane conductance regulator , cystic fibrosis , chemistry , thyroid , endocrinology , medicine , biology , microbiology and biotechnology
The cystic fibrosis transmembrane conductance regulator (CFTR) is both an anion channel and a regulator of other transport proteins. Mutations in the CFTR gene underlie the human disease, cystic fibrosis. The most common CFTR mutation, ΔF508, produces a misfolded protein which traffics improperly. The availability of transgenic CFTR ΔF508/ΔF508 pigs allows measurement of the impact of ΔF508 in native tissue. Thyroid epithelia respond to cAMP‐elevating agents by increasing anion transport, a process reliant on functional CFTR. To assess whether endogenous levels of ΔF508‐CFTR mediate thyroid transport, primary thyroid epithelial cultures (pThECs) were grown from newborn CFTR +/+ (wild‐type) and CFTR ΔF508/ΔF508 (ΔF) pig thyroids and the stimulated, secretory components of short‐circuit current ( I sc ) compared. Surface biotinylation studies assessed the surface presentation of ΔF508‐CFTR. Baseline I sc levels of both wild‐type and ΔF pThECs consisted of an amiloride‐sensitive component. In ΔF pThECs, this mirrored previous measurements in CFTR −/− (knockout) pThECs. Surprisingly, elevation of cAMP transiently increased I sc to peak levels ∼65% of those achieved by wild‐type. In contrast, knockout pThECs were indifferent to cAMP activation. In ΔF pThECs, total ΔF508‐CFTR expression was ∼9% that of wild‐type, consistent with misfolding and enhanced degradation. Surface biotinylation studies indicated that ∼4% of the total ΔF508 resided at the surface and did not increase with cAMP elevation. The present findings show that low endogenous levels of pig ΔF508‐CFTR can mediate substantial anion transport by thyroid epithelia. These data suggest that both wild‐type and ΔF508‐CFTR regulate additional thyroid transporters, and together co‐ordinate the overall I sc response.