scholarly journals Apical Ca2+-activated potassium channels in mouse parotid acinar cells

2012 ◽  
Vol 139 (2) ◽  
pp. 121-133 ◽  
Author(s):  
Janos Almassy ◽  
Jong Hak Won ◽  
Ted B. Begenisich ◽  
David I. Yule
Keyword(s):  
Plasma Membrane ◽  
Digital Imaging ◽  
Acinar Cells ◽  
Fluid Secretion ◽  
Bk Channels ◽  
Apical Plasma Membrane ◽  
K Channels ◽  
Parotid Acinar Cells ◽  
Cl Channels ◽  
K Currents

Ca2+ activation of Cl and K channels is a key event underlying stimulated fluid secretion from parotid salivary glands. Cl channels are exclusively present on the apical plasma membrane (PM), whereas the localization of K channels has not been established. Mathematical models have suggested that localization of some K channels to the apical PM is optimum for fluid secretion. A combination of whole cell electrophysiology and temporally resolved digital imaging with local manipulation of intracellular [Ca2+] was used to investigate if Ca2+-activated K channels are present in the apical PM of parotid acinar cells. Initial experiments established Ca2+-buffering conditions that produced brief, localized increases in [Ca2+] after focal laser photolysis of caged Ca2+. Conditions were used to isolate K+ and Cl− conductances. Photolysis at the apical PM resulted in a robust increase in K+ and Cl− currents. A localized reduction in [Ca2+] at the apical PM after photolysis of Diazo-2, a caged Ca2+ chelator, resulted in a decrease in both K+ and Cl− currents. The K+ currents evoked by apical photolysis were partially blocked by both paxilline and TRAM-34, specific blockers of large-conductance “maxi-K” (BK) and intermediate K (IK), respectively, and almost abolished by incubation with both antagonists. Apical TRAM-34–sensitive K+ currents were also observed in BK-null parotid acini. In contrast, when the [Ca2+] was increased at the basal or lateral PM, no increase in either K+ or Cl− currents was evoked. These data provide strong evidence that K and Cl channels are similarly distributed in the apical PM. Furthermore, both IK and BK channels are present in this domain, and the density of these channels appears higher in the apical versus basolateral PM. Collectively, this study provides support for a model in which fluid secretion is optimized after expression of K channels specifically in the apical PM.

scholarly journals Differential Regulation of the Apical Plasma Membrane Ca2+-ATPase by Protein Kinase A in Parotid Acinar Cells

2007 ◽  
Vol 282 (52) ◽  
pp. 37678-37693 ◽  
Author(s):  
Erin Baggaley ◽  
Stuart McLarnon ◽  
Irma Demeter ◽  
Gabor Varga ◽  
Jason I. E. Bruce
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase ◽  
Protein Kinase A ◽  
Acinar Cells ◽  
Differential Regulation ◽  
Apical Plasma Membrane ◽  
Parotid Acinar Cells ◽  
Kinase A

Activation of muscarinic receptors in rat parotid acinar cells induces AQP5 trafficking to nuclei and apical plasma membrane

2015 ◽  
Vol 1850 (4) ◽  
pp. 784-793 ◽  
Author(s):  
Gota Cho ◽  
Aneta M. Bragiel ◽  
Di Wang ◽  
Tomasz D. Pieczonka ◽  
Mariusz T. Skowronski ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Muscarinic Receptors ◽  
Acinar Cells ◽  
Apical Plasma Membrane ◽  
Parotid Acinar Cells ◽  
Rat Parotid

Calcium-activated potassium channels and fluid secretion by exocrine glands

1986 ◽  
Vol 251 (1) ◽  
pp. G1-G13 ◽  
Author(s):  
O. H. Petersen
Keyword(s):  
Single Channel ◽  
Basolateral Membrane ◽  
Acinar Cells ◽  
Fluid Secretion ◽  
Exocrine Glands ◽  
K Channels ◽  
Luminal Membrane ◽  
Channel Opening ◽  
Cell Current ◽  
Cl Channels

Fluid secretion by exocrine glands is regulated by neurotransmitters and hormones. The secretagogues act on the acinar cells by switching on two types of conductance pathways: K+-selective channels in the basolateral membrane and Cl(-)-selective channels localized to the luminal membrane. The K+ channels have been quantitatively characterized in patch-clamp single-channel and whole-cell current-recording studies. Opening of the K+ channels is determined by the membrane potential (depolarization enhances the probability of channel opening), and the intracellular free Ca2+ concentration ([Ca2+]i) (a rise in [Ca2+]i increases the open-state probability). The Cl- channels are also controlled by internal Ca2+ in such a way that an elevation of [Ca2+]i favors opening. Secretagogues evoking an increase in [Ca2+]i activate both sets of channels causing a substantial loss of cellular KCl. KCl is taken up via a Na+-K+-2Cl- cotransport mechanism in the basolateral membrane and the Na+ uptake activates the Na+-K+ pump. In the steady-state stimulated situation the three basolateral transport proteins, the K+ channels, the Na+-K+ pump, and the Na+-K+-2Cl- cotransporter operate together as an electrogenic Cl- pump. Cl- exits into the lumen via the Ca2+-activated Cl- channels and Na+ follows through the paracellular shunt pathway. When stimulation of the acinar cells ceases the K+ and Cl- conductance pathways close and the Na+-K+ pump together with the Na+-K+-2Cl- cotransporter operate as a KCl pump, restoring the intracellular KCl lost initially after start of stimulation and secretion stops.

scholarly journals Redistribution of a rab3-like GTP-binding protein from secretory granules to the Golgi complex in pancreatic acinar cells during regulated exocytosis

1994 ◽  
Vol 124 (1) ◽  
pp. 43-53 ◽  
Author(s):  
BP Jena ◽  
FD Gumkowski ◽  
EM Konieczko ◽  
GF von Mollard ◽  
R Jahn ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Golgi Complex ◽  
Binding Protein ◽  
Secretory Granules ◽  
Acinar Cells ◽  
Pancreatic Acinar Cells ◽  
Apical Plasma Membrane ◽  
Gtp Binding Protein ◽  
Regulated Exocytosis ◽  
Gtp Binding

Regulated secretion from pancreatic acinar cells occurs by exocytosis of zymogen granules (ZG) at the apical plasmalemma. ZGs originate from the TGN and undergo prolonged maturation and condensation. After exocytosis, the zymogen granule membrane (ZGM) is retrieved from the plasma membrane and ultimately reaches the TGN. In this study, we analyzed the fate of a low M(r) GTP-binding protein during induced exocytosis and membrane retrieval using immunoblots as well as light and electron microscopic immunocytochemistry. This 27-kD protein, identified by a monoclonal antibody that recognizes rab3A and B, may be a novel rab3 isoform. In resting acinar cells, the rab3-like protein was detected primarily on the cytoplasmic face of ZGs, with little labeling of the Golgi complex and no significant labeling of the apical plasmalemma or any other intracellular membranes. Stimulation of pancreatic lobules in vitro by carbamylcholine for 15 min, resulted in massive exocytosis that led to a near doubling of the area of the apical plasma membrane. However, no relocation of the rab3-like protein to the apical plasmalemma was seen. After 3 h of induced exocytosis, during which time approximately 90% of the ZGs is released, the rab3-like protein appeared to translocate to small vesicles and newly forming secretory granules in the TGN. No significant increase of the rab3-like protein was found in the cytosolic fraction at any time during stimulation. Since the protein is not detected on the apical plasmalemma after stimulation, we conclude that recycling may involve a membrane dissociation-association cycle that accompanies regulated exocytosis.

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