Convergence of Ca2+-desensitizing mechanisms activated by forskolin and phenylephrine pretreatment, but not 8-bromo-cGMP.
Convergence of Ca2+-desensitizing mechanisms activated by forskolin and phenylephrine pretreatment, but not 8-bromo-cGMP.
复制标题
毛喉素和去氧肾上腺素预处理激活的 Ca2+ 脱敏机制的收敛，但 8-溴-cGMP 不激活。
DOI：
10.1152/ajpcell.00534.2005
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Ratz,PaulH
中科院分区：
文献类型：
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作者：
Porter,Melissa;Evans,MelissaC;Miner,AmyS;Berg,KrystinaM;Ward,KevinR;Ratz,PaulH
收缩刺激可以激活抑制肌球蛋白轻链磷酸酶(MLCP)活性的RhoA激酶(ROK)和PKC，从而使肌球蛋白对钙离子敏感。松弛刺激通过PKA和PKG(环核苷酸依赖蛋白激酶)起作用，并用苯肾上腺素(PE)等收缩药预处理，可使肌球蛋白对钙离子不敏感。目前尚不清楚这些刺激是如何导致钙离子脱敏的。为了验证PKA、PKG和PE预处理信号系统在完整、分离的组织中通过抑制韩国而导致松弛的假设，我们研究了Forskolin(FSK；PKA激活)、8-bromo-cGMP(8BR-cGMP；PKG激活)和PE预处理对KCl诱导的兔动脉力量维持的影响，这一反应几乎完全依赖于韩国的激活。PE预处理和激活PKA和PKG的试剂通过抑制KCl诱导的紧张力和MLC的磷酸化而不抑制细胞内[Ca~(2+)]而导致Ca~(2+)脱敏。在β-ESCIN通透性肌肉的PCA5处，FSK和8b-cGMP加速了组织恢复到PCA9的松弛速度，提示两种药物都能提高MLCP的活性。然而，在完整的组织中，被归因于PKG激活的钙脱敏的一个成分似乎涉及MLC磷酸化不依赖的成分。8b-cGMP可协同增强韩国抑制剂Y-27632和PE预处理对KCl2诱导的紧张力的抑制作用，而FSK对此作用不明显。FSK和PE预处理可抑制KCl诱导的Thr853位点特异性肌球蛋白磷酸酶靶蛋白-1磷酸化的增加，而8b-cGMP则不能。这些数据支持这一假说，即PKA和PE预处理汇聚在一条共同的钙脱敏途径上，但PKG的作用机制与PKA和PE预处理激活的机制不同。
Contractile stimuli can sensitize myosin to Ca2+by activating RhoA kinase (ROK) and PKC that inhibit myosin light chain phosphatase (MLCP) activity. Relaxant stimuli, acting through PKA and PKG (cyclic nucleotide-dependent protein kinases), and pretreatment with contractile agents such as phenylephrine (PE), can desensitize myosin to Ca2+. It is unknown precisely how these stimuli cause Ca2+desensitization. To test the hypothesis that PKA, PKG, and PE pretreatment signaling systems converge to cause relaxation by inhibition of ROK in intact, isolated tissues, we examined the effects of forskolin (FSK; PKA activation), 8-bromo-cGMP (8br-cGMP; PKG activation), and PE pretreatment on KCl-induced force maintenance in rabbit arteries, a response nearly completely dependent on ROK activation. PE pretreatment and agents activating PKA and PKG caused Ca2+desensitization by inhibiting KCl-induced tonic force and MLC phosphorylation without inhibiting intracellular [Ca2+]. At pCa 5 in β-escin-permeabilized muscle, FSK and 8b-cGMP accelerated the relaxation rate when tissues were returned to pCa 9, suggesting that both agents can elevate MLCP activity. However, a component of the Ca2+desensitization attributed to PKG activation in intact tissues appeared to involve a MLC phosphorylation-independent component. Inhibition of KCl-induced tonic force by the ROK inhibitor, Y-27632, and by PE pretreatment, were synergistically potentiated by 8b-cGMP, but not FSK. FSK and PE pretreatment, but not 8b-cGMP, inhibited the KCl-induced increase in site-specific myosin phosphatase target protein-1 phosphorylation at Thr853. These data support the hypothesis that PKA and PE pretreatment converge on a common Ca2+-desensitization pathway, but that PKG can act by a mechanism different from that activated by PKA and PE pretreatment.