Margatoxin Binds to a Homomultimer of KV1.3 Channels in Jurkat Cells. Comparison with KV1.3 Expressed in CHO Cells

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• 作者：Lisa M. H. Helms ; John P. Felix ; Randal M. Bugianesi ; Maria L. Garcia ; Scott Stevens ; Reid J. Leonard ; Hans-Gü ; nther Knaus ; Robert Koch ; Siegmund G. Wanner ; Gregory J. Kaczorowski ; and Robert S. S
• 刊名：Biochemistry
• 出版年：1997
• 出版时间：March 25, 1997
• 年：1997
• 卷：36
• 期：12
• 页码：3737 - 3744
• 全文大小：165K
• 年卷期：v.36,no.12(March 25, 1997)
• ISSN：1520-4995

文摘

Voltage-gated potassium (K_V) channels playkey roles in setting the resting potential and inthe activation cascade of human peripheral T lymphocytes.Margatoxin (MgTX), a 39-amino acid peptidefrom Centruroides margaritatus, is a potentinhibitor of lymphocyte K_V channels. The bindingofmonoiodotyrosinyl margatoxin ([¹²⁵I]MgTX) to plasmamembranes prepared from either Jurkat cells, ahuman leukemic T cell line, or CHO cells stably transfected with theShaker-type voltage-gated K⁺channel,K_V1.3, has been used to investigate the properties oflymphocyte K_V channels. These data werecomparedwith [¹²⁵I]MgTX binding to heterotetramericK_V channels in rat brain synaptic plasma membranes[Knaus,H. G., et al. (1995) Biochemistry 34, 13627-13634].The affinity for [¹²⁵I]MgTX is 100-200 fMineither Jurkat or CHO/K_V1.3 membranes, and the receptordensity is 20-120 fmol/mg in Jurkat membranesor 1000 fmol/mg in CHO/K_V1.3 membranes. In contrast torat brain, [¹²⁵I]MgTX binding to JurkatandCHO/K_V1.3 membranes exhibits an absolute requirement forK⁺, with no potentiation of binding byNa⁺.K_V1.3 was the only K_V1 series channelpresent in either CHO/K_V1.3 or Jurkat plasma membranesasdetermined by immunoprecipitation of [¹²⁵I]MgTXbinding or by Western blot analyses using sequence-specific antibodies prepared against members of the K_V1family. The relative potencies of a series ofpeptidyl K_V channel inhibitors was essentially the same forinhibition of [¹²⁵I]MgTX binding to Jurkat,CHO, or rat brain membranes and for blocking⁸⁶Rb⁺ efflux from theCHO/K_V1.3 cells, except that-dendrotoxin was more potent at blocking binding to rat brainmembranes than in the other assays. Thecharacteristics of [¹²⁵I]MgTX binding, the antibodyprofiles, and the effects of the peptidyl K_Vinhibitorsall indicate that the [¹²⁵I]MgTX receptor in Jurkatlymphocytes is comprised of a homomultimer ofK_V1.3,unlike the heteromultimeric arrangement of the receptor in ratbrain.