Ca²⁺-mediated potentiation of the swelling-induced taurine efflux from HeLa cells: On the role of calmodulin and novel protein kinase C isoforms

TY - JOUR

T1 - Ca2+-mediated potentiation of the swelling-induced taurine efflux from HeLa cells: On the role of calmodulin and novel protein kinase C isoforms

AU - Falktoft, Birgitte

AU - Lambert, Ian H.

N1 - Keywords Histamine - Bradykinin - H1-receptor - PMA - Regulatory Volume Decrease

PY - 2004

Y1 - 2004

N2 - The present work sets out to investigate how Ca2+ regulates the volume-sensitive taurine-release pathway in HeLa cells. Addition of Ca2+-mobilizing agonists at the time of exposure to hypotonic NaCl medium augments the swelling-induced taurine release and subsequently accelerates the inactivation of the release pathway. The accelerated inactivation is not observed in hypotonic Ca2+-free or high-K+ media. Addition of Ca2+-mobilizing agonists also accelerates the regulatory volume decrease, which probably reflects activation of Ca2+-activated K+ channels. The taurine release from control cells and cells exposed to Ca2+ agonists is equally affected by changes in cell volume, application of DIDS and arachidonic acid, indicating that the volume-sensitive taurine leak pathway mediates the Ca2+-augmented taurine release. Exposure to Ca2+-mobilizing agonists prior to a hypotonic challenge also augments a subsequent swelling-induced taurine release even though the intracellular Ca2+-concentration has returned to the unstimulated level. The Ca2+-induced augmentation of the swelling-induced taurine release is abolished by inhibition of calmodulin, but unaffected by inhibition of calmodulin-dependent kinase II, myosin light chain kinase and calcineurin. The effect of Ca2+-mobilizing agonists is mimicked by protein kinase C (PKC) activation and abolished in the presence of the PKC inhibitor Gö6850 and following downregulation of phorbol ester-sensitive PKC isoforms. It is suggested that Ca2+ regulates the volume-sensitive taurine-release pathway through activation of calmodulin and PKC isoforms belonging to the novel subclass (nPKC).

AB - The present work sets out to investigate how Ca2+ regulates the volume-sensitive taurine-release pathway in HeLa cells. Addition of Ca2+-mobilizing agonists at the time of exposure to hypotonic NaCl medium augments the swelling-induced taurine release and subsequently accelerates the inactivation of the release pathway. The accelerated inactivation is not observed in hypotonic Ca2+-free or high-K+ media. Addition of Ca2+-mobilizing agonists also accelerates the regulatory volume decrease, which probably reflects activation of Ca2+-activated K+ channels. The taurine release from control cells and cells exposed to Ca2+ agonists is equally affected by changes in cell volume, application of DIDS and arachidonic acid, indicating that the volume-sensitive taurine leak pathway mediates the Ca2+-augmented taurine release. Exposure to Ca2+-mobilizing agonists prior to a hypotonic challenge also augments a subsequent swelling-induced taurine release even though the intracellular Ca2+-concentration has returned to the unstimulated level. The Ca2+-induced augmentation of the swelling-induced taurine release is abolished by inhibition of calmodulin, but unaffected by inhibition of calmodulin-dependent kinase II, myosin light chain kinase and calcineurin. The effect of Ca2+-mobilizing agonists is mimicked by protein kinase C (PKC) activation and abolished in the presence of the PKC inhibitor Gö6850 and following downregulation of phorbol ester-sensitive PKC isoforms. It is suggested that Ca2+ regulates the volume-sensitive taurine-release pathway through activation of calmodulin and PKC isoforms belonging to the novel subclass (nPKC).

U2 - 10.1007/s00232-004-0705-6

DO - 10.1007/s00232-004-0705-6

M3 - Journal article

C2 - 15630544

SN - 0022-2631

VL - 201

SP - 59

EP - 75

JO - Journal of Membrane Biology

JF - Journal of Membrane Biology

IS - 2

ER -