Shui Z, Khan I A, Tsuga H, Dobrzynski H, Haga T, Henderson Z, Boyett M R
School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom.
Am J Physiol Heart Circ Physiol. 2002 Aug;283(2):H819-28. doi: 10.1152/ajpheart.00515.2001.
Desensitization of the cardiac muscarinic K+ channel was studied in cultured neonatal rat atrial cells and in Chinese hamster ovary (CHO) cells transfected with muscarinic receptor (HM(2)), G protein-coupled inward rectifying K+ channels 1 and 4, and G protein-coupled receptor kinase 2. In atrial cells incubated in 10 microM carbachol for 24 h, channel activity in cell-attached patches was substantially reduced as a result of long-term desensitization. The long-term desensitization was also observed in CHO cells transfected with the wild-type receptor and receptor kinase (as well as the channel). However, long-term desensitization was greatly reduced or abolished if the cells were 1) not transfected with the receptor kinase, 2) transfected with a mutant receptor lacking phosphorylation sites (rather than the wild-type receptor), or 3) transfected with a mutant receptor kinase lacking kinase activity (rather than the wild-type receptor kinase). We suggest that long-term desensitization of the cardiac muscarinic receptor-K+ channel system to muscarinic agonist may involve phosphorylation of the receptor by receptor kinase.
在培养的新生大鼠心房细胞以及转染了毒蕈碱受体（HM(2)）、G蛋白偶联内向整流钾通道1和4以及G蛋白偶联受体激酶2的中国仓鼠卵巢（CHO）细胞中，研究了心脏毒蕈碱钾通道的脱敏作用。在含有10微摩尔卡巴胆碱的培养液中孵育24小时的心房细胞中，由于长期脱敏，细胞贴附式膜片钳中的通道活性显著降低。在转染了野生型受体和受体激酶（以及通道）的CHO细胞中也观察到了长期脱敏。然而，如果细胞：1）未转染受体激酶；2）转染了缺乏磷酸化位点的突变型受体（而非野生型受体）；或3）转染了缺乏激酶活性的突变型受体激酶（而非野生型受体激酶），则长期脱敏会大大降低或消除。我们认为，心脏毒蕈碱受体 - 钾通道系统对毒蕈碱激动剂的长期脱敏可能涉及受体激酶对受体的磷酸化作用。
