Rescue of dysfunctional deltaF508-CFTR chloride channel activity by IBMX.
Rescue of dysfunctional deltaF508-CFTR chloride channel activity by IBMX.
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IBMX 拯救功能失调的 deltaF508-CFTR 氯离子通道活性。
DOI：
10.1007/s002329900537
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Bridges,RJ
中科院分区：
文献类型：
--
作者：
Schultz,BD;Frizzell,RA;Bridges,RJ
Nucleotide-dependent gating of ΔF508-CFTR was evaluated in membrane patches excised from HEK 293 and mouse L-cells and compared to observations onwt-CFTR channels recorded in the same expression systems. ΔF508-CFTR exhibited PKA activated, ATP-dependent channel gating. When compared towt-CFTR, theKmfor ATP was increased by ninefold (260 μmvs.28 μm) and maximal open probability (Po) was reduced by 49% (0.21 ± 0.06vs.0.41 ± 0.02). Additionally, in the absence of PKA, ΔF508-CFTR inactivated over a 1 to 5 min period whereaswt-CFTR remained active. Time-dependent inactivation could be mimicked inwt-CFTR by the intermittent absence of ATP in the cytosolic solution. The effects of 3-isobutyl-1-methyl xanthine (IBMX), a compound reported to stimulate ΔF508-CFTR, were evaluated onwt- and ΔF508-CFTR channels. At concentrations up to 5 mm, IBMX caused a concentration dependent reduction in the observed single channel amplitude (i) ofwt-CFTR (maximal observed reduction 35 ± 3%). However, IBMX failed to significantly alter total patch current because of a concomitant 30% increase inPo. The effects of IBMX on ΔF508-CFTR were similar to effects onwt-CFTR in thatiwas reduced andPowas increased by similar magnitudes. Additionally, ΔF508-CFTR channel inactivation was dramatically slowed by IBMX. These results suggest that IBMX interacts with the ATP-bound open state of CFTR to introduce a short-lived nonconducting state which prolongs burst duration and reduces apparent single channel amplitude. A secondary effect observed in ΔF508-CFTR, which may result from this interaction, is a prolongation of the activated state. In light of previously proposed linear kinetic models of CFTR gating, these results suggest that IBMX traps CFTR in an ATP-bound state which may preclude inactivation of ΔF508-CFTR.
