Basal and angiotensin II-inhibited neuronal delayed-rectifier K+ current are regulated by thioredoxin

• Published in: American Journal of Physiology: Cell Physiology 2007-07, Vol.293 (1), p.C211-C217
• Main Authors: Matsuura, Tomokazu, Harrison, Rachael A, Westwell, Andrew D, Nakamura, Hajime, Martynyuk, Anatoly E, Sumners, Colin
• Format: Article
• Language: English
• Subjects: ACE inhibitors; Angiotensin II - metabolism; Angiotensin II - pharmacology; Animals; Animals, Newborn; Benzothiazoles - pharmacology; Brain; Brain Stem - cytology; Brain Stem - drug effects; Brain Stem - enzymology; Brain Stem - metabolism; Cells, Cultured; Cyclohexanones - pharmacology; Delayed Rectifier Potassium Channels - drug effects; Delayed Rectifier Potassium Channels - metabolism; Dose-Response Relationship, Drug; Hypothalamus - drug effects; Hypothalamus - enzymology; Hypothalamus - metabolism; Ion Channel Gating - drug effects; Membrane Potentials; Neurons; Neurons - drug effects; Neurons - enzymology; Neurons - metabolism; Patch-Clamp Techniques; Protein Disulfide Reductase (Glutathione) - metabolism; Proteins; Rats; Rats, Sprague-Dawley; RNA, Messenger - metabolism; Studies; Thioredoxins - antagonists & inhibitors; Thioredoxins - genetics; Thioredoxins - metabolism; Thioredoxins - pharmacology; Time Factors; Up-Regulation
• ISSN: 0363-6143; 1522-1563
• DOI: 10.1152/ajpcell.00615.2006

1 Department of Physiology and Functional Genomics and McKnight Brain Institute, University of Florida, Gainesville, Florida; 2 Department of Medicinal Chemistry, Welsh School of Pharmacy, Cardiff University, Cardiff, United Kingdom; 3 Department of Experimental Therapeutics, Translational Research Center, Kyoto University Hospital, Sakyo, Kyoto, Japan; and 4 Department of Anesthesiology, University of Florida, Gainesville, Florida Submitted 11 December 2006 ; accepted in final form 12 March 2007 In previous studies, we determined that macrophage migration inhibitory factor (MIF), acting intracellularly via its intrinsic thiol-protein oxidoreductase (TPOR) activity, stimulates basal neuronal delayed-rectifier K + current ( I Kv ) and inhibits basal and angiotensin (ANG) II-induced increases in neuronal activity. These findings are the basis for our hypothesis that MIF is a negative regulator of ANG II actions in neurons. MIF has recently been recategorized as a member of the thioredoxin (Trx) superfamily of small proteins. In the present study we have examined whether Trx influences basal and ANG II-modulated I Kv in an effort to determine whether the Trx superfamily can exert a general regulatory influence over neuronal activity and the actions of ANG II. Intracellular application of Trx (0.8–80 nM) into rat hypothalamic/brain stem neurons in culture increased neuronal I Kv , as measured by voltage-clamp recordings. This effect of Trx was abolished in the presence of the TPOR inhibitor PMX 464 (800 nM). Furthermore, the mutant protein recombinant human C32S/C35S-Trx, which lacks TPOR activity, failed to alter neuronal I Kv . Trx applied at a concentration (0.08 nM) that does not alter basal I Kv abolished the inhibition of neuronal I Kv produced by ANG II (100 nM). Given our observation that ANG II increases Trx levels in neuronal cultures, it is possible that Trx (like MIF) has a negative regulatory role over basal and ANG II-stimulated neuronal activity via modulation of I Kv . Moreover, these data suggest that TPOR may be a general mechanism for negatively regulating neuronal activity. thiol-protein oxidoreductase; patch clamp; neuronal activity Address for reprint requests and other correspondence: C. Sumners, Dept. of Physiology and Functional Genomics, College of Medicine, Univ. of Florida, Box 100274, 1600 SW Archer Rd., Gainesville, FL 32610-0274 (e-mail: csumners{at}phys.med.ufl.edu )