Cytosolic Cl- ions in the regulation of secretory and endocytotic activity in melanotrophs from mouse pituitary tissue slices

TY - JOUR

T1 - Cytosolic Cl- ions in the regulation of secretory and endocytotic activity in melanotrophs from mouse pituitary tissue slices

AU - Turner, Jan-Eric

AU - Sedej, Simon

AU - Rupnik, Marjan

AU - Turner, Jan Eric

PY - 2005/7/15

Y1 - 2005/7/15

N2 - Cl- ions are known regulators of Ca2+ -dependent secretory activity in many endocrine cells. The suggested mechanisms of Cl- action involve the modulation of GTP-binding proteins, voltage-activated calcium channels or maturation of secretory vesicles. We examined the role of cytosolic Cl- ([Cl-]i) and Cl- currents in the regulation of secretory activity in mouse melanotrophs from fresh pituitary tissue slices by using the whole-cell patch-clamp. We confirmed that elevated [Cl-]i augments Ca2- -dependent exocytosis and showed that Cl- acts on secretory vesicle maturation. The latter process was abolished by a V-type H- -ATPase blocker (bafilomycin), intracellular 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS), a Cl- channel blocker, and tolbutamide, a sulphonylurea implicated in secretory vesicle maturation. In a small subset of cells, block of plasmalemmal Cl- current by DIDS reversibly enhanced endocytosis. The direct activation of G-proteins by GTP-gamma-S, a non-hydrolysable GTP analogue, did not restore the impaired secretion observed in low [Cl-]i conditions. The amplitude of voltage-activated calcium currents was unaffected by the [Cl-]i. Furthermore, two Cl- -permeable channels, calcium-activated Cl- channels and GABAA receptors, appeared as major regulators of intracellular Cl- homeostasis. In conclusion, the predominant underlying mechanism of Cl- action is mediated by intracellular Cl- fluxes during vesicle maturation, rather than activation of G-proteins or modulation of voltage-activated Ca2+channels.

AB - Cl- ions are known regulators of Ca2+ -dependent secretory activity in many endocrine cells. The suggested mechanisms of Cl- action involve the modulation of GTP-binding proteins, voltage-activated calcium channels or maturation of secretory vesicles. We examined the role of cytosolic Cl- ([Cl-]i) and Cl- currents in the regulation of secretory activity in mouse melanotrophs from fresh pituitary tissue slices by using the whole-cell patch-clamp. We confirmed that elevated [Cl-]i augments Ca2- -dependent exocytosis and showed that Cl- acts on secretory vesicle maturation. The latter process was abolished by a V-type H- -ATPase blocker (bafilomycin), intracellular 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS), a Cl- channel blocker, and tolbutamide, a sulphonylurea implicated in secretory vesicle maturation. In a small subset of cells, block of plasmalemmal Cl- current by DIDS reversibly enhanced endocytosis. The direct activation of G-proteins by GTP-gamma-S, a non-hydrolysable GTP analogue, did not restore the impaired secretion observed in low [Cl-]i conditions. The amplitude of voltage-activated calcium currents was unaffected by the [Cl-]i. Furthermore, two Cl- -permeable channels, calcium-activated Cl- channels and GABAA receptors, appeared as major regulators of intracellular Cl- homeostasis. In conclusion, the predominant underlying mechanism of Cl- action is mediated by intracellular Cl- fluxes during vesicle maturation, rather than activation of G-proteins or modulation of voltage-activated Ca2+channels.

KW - Algorithms

KW - Animals

KW - Calcium

KW - Calcium Signaling

KW - Cell Membrane

KW - Chlorides

KW - Cytosol

KW - Electrophysiology

KW - Endocytosis

KW - Exocytosis

KW - Male

KW - Melanins

KW - Membrane Potentials

KW - Mice

KW - Patch-Clamp Techniques

KW - Pituitary Gland

KW - Receptors, GABA-A

KW - gamma-Aminobutyric Acid

U2 - 10.1113/jphysiol.2005.088997

DO - 10.1113/jphysiol.2005.088997

M3 - SCORING: Journal article

C2 - 15890700

VL - 566

SP - 443

EP - 453

JO - J PHYSIOL-LONDON

JF - J PHYSIOL-LONDON

SN - 0022-3751

IS - Pt 2

ER -