期刊
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
卷 290, 期 3, 页码 H1278-H1288出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.00777.2005
关键词
rapidly activating delayed rectifier potassium current; enzymes; myocyte isolation
资金
- NHLBI NIH HHS [R01-HL-71092, R01-HL-60723, R01-HL-68868, R01-HL-61537] Funding Source: Medline
KCNH2 (hERG1) encodes the alpha-subunit proteins for the rapidly activating delayed rectifier K+ current (I-Kr), a major K+ current for cardiac myocyte repolarization. In isolated myocytes I-Kr frequently is small in amplitude or absent, yet KCNH2 channels and I-Kr are targets for drug block or mutations to cause long QT syndrome. We hypothesized that KCNH2 channels and I-Kr are uniquely sensitive to enzymatic damage. To test this hypothesis, we studied heterologously expressed K+, Na+, and L-type Ca2+ channels, and in ventricular myoctyes I-Kr, slowly activating delayed rectifier K+ current (I-Ks), and inward rectifier K+ current (I-K1), by using electrophysiological and biochemical methods. 1) Specific exogenous serine proteases (protease XIV, XXIV, or proteinase K) selectively degraded KCNH2 current (I-KCNH2) and its mature channel protein without damaging cell integrity and with minimal effects on the other channel currents; 2) immature KCNH2 channel protein remained intact; 3) smaller molecular mass KCNH2 degradation products appeared; 4) protease XXIV selectively abolished I-Kr; and 5) reculturing HEK-293 cells after protease exposure resulted in the gradual recovery of I-KCNH2 and its mature channel protein over several hours. Thus the channel protein for I-KCNH2 and I-Kr is uniquely sensitive to proteolysis. Analysis of the degradation products suggests selective proteolysis within the S5-pore extracellular linker, which is structurally unique among Kv channels. These data provide 1) a new mechanism to account for low I-Kr density in some isolated myocytes, 2) evidence that most complexly glycosylated KCNH2 channel protein is in the plasma membrane, and 3) new insight into the rate of biogenesis of KCNH2 channel protein within cells.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据