ATP and PIP2 dependence of the magnesium-inhibited, TRPM7-like cation channel in cardiac myocytes
ATP and PIP2 dependence of the magnesium-inhibited, TRPM7-like cation channel in cardiac myocytes
复制标题
DOI：
10.1152/ajpcell.00074.2006
复制
发表时间：
2006-10-01
影响因子：
5.5
通讯作者：
Mubagwa, Kanigula
中科院分区：
文献类型：
--
作者：
Gwanyanya, Asfree;Sipido, Karin R.;Mubagwa, Kanigula
心肌细胞中的Mg 2+抑制阳离子（MIC）电流（I-MIC）在生物学上类似于异源表达的瞬时受体电位（TRP）通道的电流，特别是已知在Mg 2+稳态中重要的TRPM 6和TRPM 7。为了了解心肌细胞MIC通道的调节，我们采用全细胞电压钳技术研究了猪、大鼠和豚鼠心室肌细胞内ATP的作用。IMIC，研究在存在或不存在的胞外二价阳离子，持续>= 50分钟后，在ATP-透析细胞的补丁破裂，而在ATP-耗尽的细胞IMIC表现出完全的破败。等摩尔的内部ATP取代其不可水解的类似物腺苷5 '-（β，γ-亚氨基）三磷酸未能防止下降。在ATP耗尽的细胞中，通过氟化物+钒酸盐+焦磷酸盐抑制脂质磷酸酶防止IMIC下降。相反，在类似的条件下，无论是蛋白磷酸酶1，2A，2B或蛋白酪氨酸磷酸酶的抑制，也不是蛋白激酶A（毛喉素，20 μ M）或蛋白激酶C（佛波醇肉豆蔻酸乙酸酯，100 nM）的激活可以防止下降。在ATP负载的细胞中，通过防止磷脂酰肌醇4，5-二磷酸（PIP 2）的再合成（10 μ M渥曼青霉素或15 μ M氧化苯胂）来消除PIP 2诱导IMIC的下降。最后，用外源性PIP 2（10 μ M）装载ATP耗尽的细胞防止了衰竭。这些结果表明，PIP 2，可能产生的ATP-利用脂质激酶，是必要的维持心脏MIC通道活性。
The Mg2+-inhibited cation (MIC) current (I-MIC) in cardiac myocytes biophysically resembles currents of heterologously expressed transient receptor potential (TRP) channels, particularly TRPM6 and TRPM7, known to be important in Mg2+ homeostasis. To understand the regulation of MIC channels in cardiac cells, we used the whole cell voltage-clamp technique to investigate the role of intracellular ATP in pig, rat, and guinea pig isolated ventricular myocytes. IMIC, studied in the presence or absence of extracellular divalent cations, was sustained for >= 50 min after patch rupture in ATP-dialyzed cells, whereas in ATP-depleted cells IMIC exhibited complete rundown. Equimolar substitution of internal ATP by its nonhydrolyzable analog adenosine 5'-(beta, gamma-imido) triphosphate failed to prevent rundown. In ATP-depleted cells, inhibition of lipid phosphatases by fluoride + vanadate + pyrophosphate prevented IMIC rundown. In contrast, under similar conditions neither the inhibition of protein phosphatases 1, 2A, 2B or of protein tyrosine phosphatase nor the activation of protein kinase A (forskolin, 20 mu M) or protein kinase C (phorbol myristate acetate, 100 nM) could prevent rundown. In ATP-loaded cells, depletion of phosphatidylinositol 4,5-bisphosphate (PIP2) by prevention of its resynthesis (10 mu M wortmannin or 15 mu M phenylarsine oxide) induced rundown of IMIC. Finally, loading ATP-depleted cells with exogenous PIP2 (10 mu M) prevented rundown. These results suggest that PIP2, likely generated by ATP-utilizing lipid kinases, is necessary for maintaining cardiac MIC channel activity.