ロドプシンリン酸化は,S-モジュリンによる周期的なGMPリン酸エステラゼの調節のメカニズムとして,S-モジュリンによるロドプシンリン酸化である
1Department of Physiology, Keio University School of Medicine, Tokyo, Japan.
Nature
|April 29, 1993
まとめ
の棒のS-モジュリンタンパク質は,活性サイクルGMP-フォスフォディエステラーゼ (PDE) の寿命を延長することによって,光の適応を加速します. このCa2+依存の調節は,ロドプシンリン酸化によって媒介され,脊椎動物の光受容体光の適応の鍵となります.
科学分野:
- 写真生物学 写真生物学
- 分子生物学は分子生物学である.
- 細胞生理学 細胞生理学
背景:
- 脊椎動物の目の光への適応には,棒の無感化と光への反応の加速が含まれる.
- 棒の光の吸収は,サイクリックGMP (cGMP) を水解する,フォスフォディエステラーゼ (PDE) を活性化します.
- サイトプラズマのCa2+濃度の低下は,光への適応に不可欠である.
研究 の 目的:
- の棒光受容体光の適応におけるS-モジュリンの役割を調査する.
- S-モジュリンが活性PDE (PDE*) とCa2+レベルに影響を与えるメカニズムを解明する.
主な方法:
- の棒光受容体におけるPDE*生涯に対するS-モジュリンの効果を研究した.
- S-モジュリンと異なるCa2+濃度でPDE活性化とロドプシンリン酸化を測定した.
- S-モジュリンの効果のためにATPの必要性を評価した.
主要な成果:
- S-モジュリンは,生理学的Ca2+濃度 (30 nM1 microM) で活性PDE (PDE*) の寿命を延長する.
- S-モジュリンは,高濃度のCa2+でロドプシンリン酸化を抑制する (半最大効果~100 nM).
- S-モジュリン媒介のPDE活性化にはATPが必要である.
結論:
- S-モジュリンのCa2+依存型PDE調節は,ロドプシンリン酸化によって媒介されます.
- このS-モジュリン-ロドプシンリン酸化経路は,脊椎動物の光受容体における光の適応の主なメカニズムである.
関連する概念動画
Channel Rhodopsins
Most organisms use photoreceptors to sense and respond to light. Examples of photoreceptors include bacteriorhodopsins and bacteriophytochromes in some bacteria, phytochromes in plants, and rhodopsins in the photoreceptor cells of the vertebral retina. The light-sensitive property of these receptors is because of the bound chromophores, such as bilin in the phytochromes and retinal in the rhodopsins.
Rhodopsins belong to the family of cell surface proteins called G-protein coupled receptors,...
Rhodopsins belong to the family of cell surface proteins called G-protein coupled receptors,...
Amplifying Signals via Enzymatic Cascade
When a ligand binds to a cell-surface receptor, the receptor's intracellular domain changes shape, which may either activate its enzyme function or allow its binding to other molecules. The initial signal is amplified by most signal transduction pathways. This means that a single ligand molecule can activate multiple molecules of a downstream target. Proteins that relay a signal are most commonly phosphorylated at one or more sites, activating or inactivating the protein. Kinases catalyze the...
Activation and Inactivation of G Proteins
Heterotrimeric G proteins are guanine nucleotide-binding proteins. As the name suggests, heterotrimeric G proteins are composed of three subunits: alpha, beta, and gamma. They remain GDP-bound or GTP-bound inside the cells and switch between inactive/active states. The Gα subunit possesses the nucleotide-binding pocket that binds guanine nucleotides and switches between GDP or GTP-bound states. In contrast, the Gꞵ and Gγ subunits are always bound together with high affinity and are together...
G-Protein Gated Ion Channels
GPCRs are primarily responsible for our sense of smell, taste, and vision. The binding of a sensory stimulus activates GPCR to stimulate effector proteins, many of which are ion channels in the sensory organs. GPCRs modulate the opening and closing of the target ion channels either directly by binding them, or by releasing second messengers that activate these channels. As ions move across the membrane, the membrane potential is altered, which induces an appropriate response.
Sensory organs,...
Sensory organs,...
GPCRs Regulate Adenylyl Cylase Activity
Some GPCRs transmit signals through adenylyl cyclase (AC), a transmembrane enzyme. AC helps synthesize second messenger cyclic adenosine monophosphate (cAMP). AC catalyzes cyclization reaction and converts ATP to cAMP by releasing a pyrophosphate. The pyrophosphate is further hydrolyzed to phosphate by the enzyme pyrophosphatase, which drives cAMP synthesis to completion. However, cAMP is rapidly degraded to 5′ AMP by the enzymes phosphodiesterase (PDE), preventing overstimulation of cells.
Two...
Two...
Calmodulin-dependent Signaling
Calmodulin (CaM) is a calcium-binding protein in eukaryotes that controls various calcium-regulated cellular processes. It has four calcium-binding sites that bind calcium to form the calcium-calmodulin ( Ca2+-CaM) complex. GPCR stimulation increases the calcium levels in the cells that bind to CaM and induces a conformational change.
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...


