Separate upstream and convergent downstream pathways of G-protein- and phorbol ester-mediated Ca2+ sensitization of myosin light chain phosphorylation in smooth muscle.
Separate upstream and convergent downstream pathways of G-protein- and phorbol ester-mediated Ca2+ sensitization of myosin light chain phosphorylation in smooth muscle.
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平滑肌中肌球蛋白轻链磷酸化的 G 蛋白和佛波酯介导的 Ca2 敏化的独立上游和会聚下游途径。
DOI：
10.1042/bj3180469
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Somlyo,AP
中科院分区：
文献类型：
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作者：
Jensen,PE;Gong,MC;Somlyo,AV;Somlyo,AP
在兔门静脉(PV)、股动脉(FA)和回肠平滑肌上，观察佛波酯诱导的蛋白激酶C(PKC)下调对二酰甘油(sn-1，2-diocanoylgarcerol，diC8)和G蛋白偶联的钙敏化作用的影响，以及调节肌球蛋白轻链(MLC20)的磷酸化与肌球蛋白轻链(MLC20)受力的关系。测定了佛波二丁酸酯(PDBu)、鸟苷5‘-[γ-硫代]三磷酸(GTP[S])和激动剂对PKC同工酶胞膜分布的影响。下调PKC可阻断PDBu引起的钙敏化和随之而来的MLC20磷酸化的增加，也可阻断DiC8对钙的敏化作用，但不能被GTP[S]、氟化铝(AlF4-)或激动剂(苯肾上腺素、内皮素或卡巴胆碱)所致。在无钙条件下，下调也能抑制PDBu-，但不能抑制GTP[S]诱导的肌力增加。在回肠，PDBu使PKCα，β1、β2、ϵ和θ移位到膜部分，而GTP[S]引起PKC-ϵ的少量移位。在未检测到胞浆PKC-ϵ的下调调节的回肠中，卡巴胆碱和葛根素[S]诱导的钙敏化作用未受影响。我们的结论是，虽然佛波酯诱导和G蛋白偶联的钙敏化都是通过增加MLC20的磷酸化来介导的，但PKCα，β1、β2、ϵ和θ可能并不在G蛋白偶联机制中起重要作用，尽管它们可能参与了G蛋白偶联机制。
The effect of phorbol ester-induced down-regulation of protein kinase C (PKC) on diacylglycerol (sn-1,2-dioctanoylglycerol, diC8)- and G-protein-coupled Ca2+sensitization and on the relationship between phosphorylation of the regulatory myosin light chains (MLC20) and force during Ca2+sensitization were investigated in rabbit portal vein (PV), femoral artery (FA) and ileum smooth muscle. The effects of phorbol dibutyrate (PDBu), guanosine 5´-[γ-thio]triphosphate (GTP[S]) and agonists on the membrane versus cytosolic distribution of PKC isoenzymes were also determined. Down-regulation of PKC abolished Ca2+sensitization of force and the accompanying increases in MLC20phosphorylation induced by PDBu, as well as Ca2+sensitization of force by diC8, but not that by GTP[S], aluminum fluoride (AlF4-) or agonists (phenylephrine, endothelin or carbachol). Down-regulation also inhibited the PDBu-, but not the GTP[S]-induced increase in force under Ca2+-free conditions. In ileum, PDBu translocated PKCs α, β1, β2, ϵ and θ to the membrane fraction, and GTP[S] caused a small translocation of PKC-ϵ. Carbachol- and GTP[S]-induced Ca2+sensitization remained unaffected in down-regulated ileum in which no cytosolic PKC-ϵ was detectable. We conclude that, although both phorbol ester-induced and G-protein-coupled Ca2+sensitization of force are mediated by increased MLC20phosphorylation, it is likely that PKCs α, β1, β2, ϵ and θ do not play an essential role in, although they may contribute to, the G-protein-coupled mechanism.