Reduction of muscarinic K + channel activity by transferrin in ischemic rat atrial myocytes

Kyeong Tae Park, Dawon Kang, Jaehee Han, Jae-Yong Park, Chang Gi Hur, Seong Geun Hong

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

It has been demonstrated that an unidentified cytosolic factor(s) reduces K ACh channel function. Therefore, this study attempted to elucidate the cytosolic factor. Fresh cytosol isolated from normal heart (FC) depressed the K ACh channel activity, but cytosol isolated from the ischemic hearts (IC) did not modulate the channel function. Electrophorectic analysis revealed that a protein of ∼80 kDa was markedly reduced or even lost in IC. By using peptide sequencing analysis and Western blot, this 80 kDa protein was identified as transferrin (receptor-mediated Fe 3+ transporter, 76 kDa). Direct application of transferrin (100 nM) to the cytoplasmic side of inside-out patches decreased the open probability (P o , 12.7±6.4%, n=4) without change in mean open time (τ o , 98.5±1.3%, n=4). However, the equimolar apotransferrin, which is free of Fe 3+ , had no effect on the channel activity (N*P o , 129.1±13.5%, n=3). Directly applied Fe 3+ (100 nM) showed results similar to those of transferrin (N*P o : 21.1±3.9%, n=5). However Fe 2+ failed to reduce the channel function (N*P o ,106.3±26.8%, n=5). Interestingly, trivalent cation La 3+ inhibited N*P o of the channel (6.1±3.0%, n=3). Taken together, these results suggest that Fe 3+ bound to transferrin can modulate the K ACh channel function by its electrical property as a polyvalent cation.

Original languageEnglish
Pages (from-to)333-339
Number of pages7
JournalKorean Journal of Physiology and Pharmacology
Volume7
Issue number6
Publication statusPublished - 2003 Dec 1
Externally publishedYes

Keywords

  • Cardiac ischemia
  • Cytosolic factor
  • Ferric iron
  • Muscarinic K channel
  • Transferrin

ASJC Scopus subject areas

  • Physiology
  • Pharmacology

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