Koegel H, Alzheimer C
Department of Physiology, University of Munich, D-80336 Munich, Germany.
FASEB J. 2001 Jan;15(1):145-154. doi: 10.1096/fj.00-0055com.
In whole-cell recordings from HaCaT keratinocytes, ATP, bradykinin, and histamine caused a biphasic change of the membrane potential consisting of an initial transient depolarization, followed by a pronounced and long-lasting hyperpolarization. Flash photolysis of caged IP3 mimicked the agonist-induced voltage response, suggesting that intracellular Ca2+ release and subsequent opening of Ca2+-activated ion channels serve as the common transduction mechanism. In contrast, cAMP- and PKC-dependent pathways were not involved in the electrophysiological effects of the extracellular signaling molecules. The depolarization was predominantly mediated by a DIDS- and niflumic acid-sensitive Cl- current, whereas a charybdotoxin- and clotrimazole-sensitive K+ current underlay the prominent hyperpolarization. Consistent with the electrophysiological data, RT-PCR showed that HaCaT keratinocytes express two types of Ca2+-activated Cl- channels, CaCC2 and CaCC3 (CLCA2), as well as the Ca2+-activated K+ channel hSK4. That the pronounced hSK4-mediated hyperpolarization bears significance on the growth and differentiation properties of keratinocytes is suggested by RNase protection assays showing that hSK4 mRNA expression is strongly down-regulated under conditions that allow keratinocyte differentiation. hSK4 might thus play a role in linking changes in membrane potential to the biological fate of keratinocytes.
在对HaCaT角质形成细胞进行的全细胞膜片钳记录中，ATP、缓激肽和组胺引起膜电位的双相变化，包括最初的短暂去极化，随后是明显且持久的超极化。笼锁IP3的闪光光解模拟了激动剂诱导的电压反应，表明细胞内Ca2+释放以及随后Ca2+激活离子通道的开放是共同的转导机制。相比之下，cAMP和PKC依赖的信号通路不参与细胞外信号分子的电生理效应。去极化主要由DIDS和氟尼酸敏感的Cl-电流介导，而突出的超极化则由蝎毒素和克霉唑敏感的K+电流介导。与电生理数据一致，RT-PCR显示HaCaT角质形成细胞表达两种类型的Ca2+激活Cl-通道，CaCC2和CaCC3（CLCA2），以及Ca2+激活的K+通道hSK4。核糖核酸酶保护试验表明，在允许角质形成细胞分化的条件下，hSK4 mRNA表达强烈下调，这表明明显的hSK4介导的超极化对角质形成细胞的生长和分化特性具有重要意义。因此，hSK4可能在将膜电位变化与角质形成细胞的生物学命运联系起来方面发挥作用。
