NDLI: KVLQT channels are inhibited by the K+ channel blocker 293B

Content Provider	Springer Nature Link
Author	Bleich, M. Briel, M. Busch, A. E. Lang, H. J. Gerlach, U. Gögelein, H. Greger, R. Kunzelmann, K.
Copyright Year	1997
Abstract	Previous data have indicated that the chromanol 293B blocks a cAMP activated K+ conductance in the colonic crypt, a K+ conductance in pig cardiac myocytes and the K+ conductance induced by IsK protein expression in Xenopus oocytes. We have also shown that cAMP-activated cystic fibrosis transmembrane conductance regulator (CFTR) up-regulates, apart from the typical Cl–current, a 293B- inhibitable K+ current. Very recently it has been shown that the IsK protein interacts with KVLQT subunits to produce a K+ channel. These data have prompted us to ask the following questions: Is the 293B-inhibitable current in oocytes expressing CFTR and activated by cAMP caused by an endogenous Xenopus KVLQT (XKVLQT), and is mouse KVLQT (mKVLQT) expressed in oocytes inhibited by 293B? Antisense and sense probes for XKVLQT were coinjected with CFTR cRNA into oocytes. After 3–4 days the oocytes were examined by two electrode voltage clamp. It was found that in control oocytes expressing CFTR and stimulated by isobutylmethylxanthine (IBMX, 1 mmol/l) 293B (10 μmol/l) reduced the conductance (Gm). In oocytes coinjected with the sense probe for XKVLQT and pretreated with IBMX 293B still reduced Gm, whilst the 293B-inhibitable Gm was almost completely absent in oocytes coinjected with XKVLQT antisense. In another series a full length clone for mKVLQT was generated by PCR techniques and the cRNA was injected into oocytes. After several days these oocytes, unlike water injected ones, were found to be strongly hyperpolarized and their Gm was increased significantly. The oocytes were depolarized significantly and their Gm was reduced reversibly by 10 μmol/l 293B. These data indicate that CFTR activation by IBMX indeed co-activates an endogenous oocyte XKVLQT channel and that this channel is inhibited by a new class of channel blockers, of which 293B is the prototype.
Starting Page	499
Ending Page	501
Page Count	3
File Format	PDF
ISSN	00316768
Journal	Pflügers Archiv
Volume Number	434
Issue Number	4
e-ISSN	14322013
Language	English
Publisher	Springer-Verlag
Publisher Date	1997-07-07
Publisher Place	Berlin, Heidelberg
Access Restriction	One Nation One Subscription (ONOS)
Content Type	Text
Resource Type	Article
Subject	Physiology Physiology (medical) Clinical Biochemistry

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