RGD Reference Report - Evidence for KCNQ1 K+ channel expression in rat zymogen granule membranes and involvement in cholecystokinin-induced pancreatic acinar secretion. - Rat Genome Database

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Evidence for KCNQ1 K+ channel expression in rat zymogen granule membranes and involvement in cholecystokinin-induced pancreatic acinar secretion.

Authors: Lee, WK  Torchalski, B  Roussa, E  Thevenod, F 
Citation: Lee WK, etal., Am J Physiol Cell Physiol. 2008 Apr;294(4):C879-92. Epub 2008 Jan 23.
RGD ID: 2317969
Pubmed: PMID:18216164   (View Abstract at PubMed)
DOI: DOI:10.1152/ajpcell.00490.2007   (Journal Full-text)

Secretion of enzymes and fluid induced by Ca(2+) in pancreatic acini is not completely understood and may involve activation of ion conductive pathways in zymogen granule (ZG) membranes. We hypothesized that a chromanol 293B-sensitive K(+) conductance carried by a KCNQ1 protein is expressed in ZG membranes (ZGM). In suspensions of rat pancreatic ZG, ion flux was determined by ionophore-induced osmotic lysis of ZG suspended in isotonic salts. The KCNQ1 blocker 293B selectively blocked K(+) permeability (IC(50) of approximately 10 microM). After incorporation of ZGM into planar bilayer membranes, cation channels were detected in 645/150 mM potassium gluconate cis/trans solutions. Channels had linear current-voltage relationships, a reversal potential (E(rev)) of -20.9 +/- 0.9 mV, and a single-channel K(+) conductance (g(K)) of 265.8 +/- 44.0 pS (n = 39). Replacement of cis 500 mM K(+) by 500 mM Na(+) shifted E(rev) to -2.4 +/- 3.6 mV (n = 3), indicating K(+) selectivity. Single-channel analysis identified several K(+) channel groups with distinct channel behaviors. K(+) channels with a g(K) of 651.8 +/- 88.0 pS, E(rev) of -22.9 +/- 2.2 mV, and open probability (P(open)) of 0.43 +/- 0.06 at 0 mV (n = 6) and channels with a g(K) of 155.0 +/- 11.4 pS, E(rev) of -18.3 +/- 1.8 mV, and P(open) of 0.80 +/- 0.03 at 0 mV (n = 3) were inhibited by 100 microM 293B or by the more selective inhibitor HMR-1556 but not by the maxi-Ca(2+)-activated K(+) channel (BK channel) inhibitor charybdotoxin (5 nM). KCNQ1 protein was demonstrated by immunoperoxidase labeling of pancreatic tissue, immunogold labeling of ZG, and immunoblotting of ZGM. 293B also inhibited cholecystokinin-induced amylase secretion of permeabilized acini (IC(50) of approximately 10 microM). Thus KCNQ1 may account for ZG K(+) conductance and contribute to pancreatic hormone-stimulated enzyme and fluid secretion.

Gene Ontology Annotations    Click to see Annotation Detail View

Cellular Component
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
zymogen granule membrane  IDA 2317969 RGD 

Objects Annotated

Genes (Rattus norvegicus)
Kcnq1  (potassium voltage-gated channel subfamily Q member 1)


Additional Information