RHODOPSIN PHOSPHORYLATION AS A MECHANISM OF CYCLIC-GMP PHOSPHODIESTERASE REGULATION BY S-MODULIN
RHODOPSIN PHOSPHORYLATION AS A MECHANISM OF CYCLIC-GMP PHOSPHODIESTERASE REGULATION BY S-MODULIN
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DOI：
10.1038/362855a0
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发表时间：
1993-04-29
期刊：
影响因子：
64.8
通讯作者：
KAWAMURA, S
中科院分区：
文献类型：
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作者：
KAWAMURA, S
在脊椎动物眼睛的光适应过程中，视杆被减敏，光响应被加速1，2。当光被视杆吸收时，磷酸二酯酶被激活，该酶水解环GMP3，4。光诱导的胞浆钙浓度下降5-7是这种光适应过程的一部分8，9。已知S-调制素(M(R)26,000)蛋白在高钙浓度时增加青蛙视杆感光器10中光激活的环GMP-磷酸二酯酶(PDE)的比例。在这里，我提出了S-调制素在高钙浓度下延长活性PDE(PDE*)寿命的证据。这些S调制效应在钙离子浓度的生理范围内(30 nM~1微米；200~400毫微米的半峰效应)观察到。在S-调制素延长PDE*寿命的高钙浓度下，S-调制素抑制视紫红质的磷酸化(在约100 nM的钙离子时呈半峰值效应)。S-调制素对PDE的激活作用离不开三磷酸腺苷。因此，我认为S-调制素对PDE的钙依赖性调节是通过视紫红质的磷酸化来实现的。这种调节似乎是脊椎动物光感受器光适应的主要机制。
DURING light-adaptation by the vertebrate eye, the rods are desensitized and the light response is accelerated1,2. When light is absorbed by the rods, a phosphodiesterase is activated that hydrolyses cyclic GMP3,4. A light-induced decrease in cytoplasmic Ca2+ concentration5-7 is part of this light-adaptation process8,9. The protein S-modulin (M(r) 26,000) is known to increase the fraction of light-activated cyclic GMP-phosphodiesterase (PDE) at high Ca2+ concentrations in frog rod photoreceptors10. Here I present evidence that S-modulin lengthens the lifetime of active PDE (PDE*) at high Ca2+ Concentrations. These S-modulin effects are observed in the physiological range of Ca2+ concentration (30 nM to 1 muM; half-maximum effects at 200-400 nM). At the high Ca2+ concentrations at which S-modulin prolongs the lifetime of PDE*, S-modulin inhibits rhodopsin phosphorylation (half-maximum effect at approximately 100 nM Ca2+). ATP is necessary for the S-modulin effects on PDE activation. I therefore conclude that the Ca2+-dependent regulation of PDE by S-modulin is mediated by rhodopsin phosphorylation. This regulation seems to be the principal mechanism of light adaptation in vertebrate photoreceptors.