scholarly journals Ca2+-activated K channels in parotid acinar cells: The functional basis for the hyperpolarized activation of BK channels

Channels ◽  
2010 ◽  
Vol 4 (4) ◽  
pp. 278-288 ◽  
Author(s):  
Victor Romanenko ◽  
Jill Thompson ◽  
Ted Begenisich
Keyword(s):  
Acinar Cells ◽  
Bk Channels ◽  
K Channels ◽  
Functional Basis ◽  
Parotid Acinar Cells

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.

New saliva secretion model based on the expression of Na+-K+ pump and K+ channels in the apical membrane of parotid acinar cells

2018 ◽  
Vol 470 (4) ◽  
pp. 613-621 ◽  
Author(s):  
János Almássy ◽  
Elias Siguenza ◽  
Marianna Skaliczki ◽  
Klara Matesz ◽  
James Sneyd ◽  
...  
Keyword(s):  
Apical Membrane ◽  
Acinar Cells ◽  
K Channels ◽  
Parotid Acinar Cells ◽  
Model Based ◽  
Saliva Secretion

scholarly journals The role of cell cholesterol and the cytoskeleton in the interaction between IK1 and maxi-K channels

2009 ◽  
Vol 296 (4) ◽  
pp. C878-C888 ◽  
Author(s):  
Victor G. Romanenko ◽  
Kurt S. Roser ◽  
James E. Melvin ◽  
Ted Begenisich
Keyword(s):  
Physical Properties ◽  
Cholesterol Level ◽  
Protein Interaction ◽  
Acinar Cells ◽  
Membrane Cholesterol ◽  
Cholesterol Depletion ◽  
K Channels ◽  
Parotid Acinar Cells ◽  
K Activity

Recently, we demonstrated a novel interaction between large-conductance (maxi-K or KCa1.1) and intermediate-conductance (IK1 or KCa3.1) Ca2+-activated K channels: activation of IK1 channels causes the inhibition of maxi-K activity (Thompson J and Begenisich T. J Gen Physiol 127: 159–169, 2006). Here we show that the interaction between these two channels can be regulated by the membrane cholesterol level in parotid acinar cells. Depletion of cholesterol using methyl-β-cyclodextrin weakened, while cholesterol enrichment increased, the ability of IK1 activation to inhibit maxi-K channels. Cholesterol's stereoisomer, epicholesterol, was unable to substitute for cholesterol in the interaction between the two K channels, suggesting a specific cholesterol-protein interaction. This suggestion was strengthened by the results of experiments in which cholesterol was replaced by coprostanol and epicoprostanol. These two sterols have nearly identical effects on membrane physical properties and cholesterol-rich microdomain stability, but had very different effects on the IK1/maxi-K interaction. In addition, the IK1/maxi-K interaction was unaltered in cells lacking caveolin, the protein essential for formation and stability of caveolae. Finally, disruption of the actin cytoskeleton restored the IK1-induced maxi-K inhibition that was lost with cell cholesterol depletion, demonstrating the importance of an intact cytoskeleton for the cholesterol-dependent regulation of the IK1/maxi-K interaction.

scholarly journals Apical Ca2+-Activated K+-Channels in Mouse Parotid Acinar Cells

2012 ◽  
Vol 102 (3) ◽  
pp. 650a-651a
Author(s):  
Janos Almassy ◽  
Ted Begenisich ◽  
David Yule
Keyword(s):  
Acinar Cells ◽  
K Channels ◽  
Parotid Acinar Cells

scholarly journals β-Adrenergic stimulation alters oligosaccharide pyrophosphoryl dolichol metabolism in rat parotid acinar cells

1985 ◽  
Vol 231 (2) ◽  
pp. 431-438 ◽  
Author(s):  
S R Grant ◽  
E E Kousvelari ◽  
D K Banerjee ◽  
B J Baum
Keyword(s):  
Half Life ◽  
Specific Radioactivity ◽  
Acinar Cells ◽  
Protein Glycosylation ◽  
Significant Enhancement ◽  
Adrenergic Stimulation ◽  
Parotid Acinar Cells ◽  
Secretory Glycoproteins ◽  
Rat Parotid ◽  
Stimulation Of

beta-Adrenergic stimulation of rat parotid acinar cells markedly increases [3H]mannose incorporation into N-linked glycoproteins [Kousvelari, Grant, Banerjee, Newby & Baum (1984) Biochem. J. 222, 17-24]. More than 90% of this protein-bound [3H]mannose was preferentially incorporated into four secretory glycoproteins. The ratio of [3H]mannose/[14C]leucine present in these individual proteins was 1.7-4-fold greater with isoproterenol-treated cells than with untreated controls. In isoproterenol-stimulated cells, [3H]mannose incorporation into mannosylphosphoryl dolichol and oligosaccharide-PP-dolichol was increased 2-3-fold over that observed in unstimulated cells. Similarly, formation of mannosylated oligosaccharide-PP-dolichol was increased approx. 4-fold in microsomes prepared from isoproterenol-treated cells. Also, turnover of oligosaccharide-PP-dolichol was significantly increased (5-fold) by β-adrenergic stimulation; the half-life for oligosaccharide-PP-dolichol decreased from 6 min in control cells to 1.2 min in isoproterenol-stimulated cells. By 15 min after isoproterenol addition to acinar cells, the specific radioactivity of parotid oligosaccharide moieties increased about 3-fold over the value observed in the absence of the agonist. Taken together, these results strongly suggest that elevation of N-linked protein glycosylation in rat parotid acinar cells after β-adrenoreceptor stimulation resulted from significant enhancement in the synthesis of mannosylphosphoryl dolichol and oligosaccharide-PP-dolichol and the turnover of oligosaccharide-PP-dolichol.

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