| Autor: |
Chen P; Department of Electrical Engineering, University of Missouri-Columbia, Columbia, MO 65211, USA., Hwang TC, Gillis KD |
| Jazyk: |
angličtina |
| Zdroj: |
The Journal of general physiology [J Gen Physiol] 2001 Aug; Vol. 118 (2), pp. 135-44. |
| DOI: |
10.1085/jgp.118.2.135 |
| Abstrakt: |
The mechanism whereby cAMP stimulates Cl(-) flux through CFTR ion channels in secretory epithelia remains controversial. It is generally accepted that phosphorylation by cAMP-dependent protein kinase increases the open probability of the CFTR channel. A more controversial hypothesis is that cAMP triggers the translocation of CFTR from an intracellular pool to the cell surface. We have monitored membrane turnover in Calu-3 cells, a cell line derived from human airway submucosal glands that expresses high levels of CFTR using membrane capacitance and FM1-43 fluorescence measurements. Using a conventional capacitance measurement technique, we observe an apparent increase in membrane capacitance in most cells that exhibit an increase in Cl(-) current. However, after we carefully correct our recordings for changes in membrane conductance, the apparent changes in capacitance are eliminated. Measurements using the fluorescent membrane marker FM1-43 also indicate that no changes in membrane turnover accompany the activation of CFTR. Robust membrane insertion can be triggered with photorelease of caged Ca(2)+ in Calu-3 cells. However, no increase in Cl(-) current accompanies Ca(2)+-evoked membrane fusion. We conclude that neither increases in cAMP or Ca(2)+ lead to transport of CFTR to the plasma membrane in Calu-3 cells. In addition, we conclude that membrane capacitance measurements must be interpreted with caution when large changes in membrane conductance occur. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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