Modulation of Large Conductance Ca<SUP>2&#8290;</SUP>-activated K<SUP>&#8290;</SUP> Channel of Skin Fibroblast (CRL-1474) by Cyclic Nucleotides

Modulation of Large Conductance Ca<SUP>2&#8290;</SUP>-activated K<SUP>&#8290;</SUP> Channel of Skin Fibroblast (CRL-1474) by Cyclic Nucleotides

Potassium channels in human skin fibroblast have been studied as a possible site of Alzheimer disease pathogenesis. Fibroblasts in Alzheimer disease show alterations in signal transduction pathway such as changes in Ca<SUP>2&#8290;</SUP> homeostasis and/or Ca<SUP>2&#8290;</SUP>-activated kinases, phosphatidylinositol cascade, protein kinase C activity, cAMP levels and absence of specific K<SUP>&#8290;</SUP> channel. However, little is known so far about electrophysiological and pharmacological characteristics of large-conductance Ca<SUP>2&#8290;</SUP>-activated K<SUP>&#8290;</SUP> (BK<SUB>Ca</SUB>) channel in human fibroblast (CRL-1474). In the present study, we found Iberiotoxin- and TEA-sensitive outward rectifying oscillatory current with whole-cell recordings. Single channel analysis showed large conductance K<SUP>&#8290;</SUP> channels (106 pS of chord conductance at &#8290;40 mV in physiological K<SUP>&#8290;</SUP> gradient). The 106 pS channels were activated by membrane potential and [Ca<SUP>2&#8290;</SUP>]<SUB>i</SUB>, consistent with the known pro</SUB>perties of BK<SUB>Ca</SUB> channels. BK<SUB>Ca</SUB> channels in CRL-1474 were positively regulated by adenylate cyclase activator (10μM forskolin), 8-Br-cyclic AMP (300μM) or 8-Br-cyclic GMP (300μM). These results suggest that human skin fibroblasts (CR-1474) have typical BK<SUB>Ca</SUB> channel and this channel could be modulated by c-AMP and c-GMP. The electrophysiological characteristics of fibroblasts might be used as the diagnostic clues for Alzheimer disease.