Epacは,循環型AMPによって直接活性化されるRap1のグアニン核酸代謝因子です
J de Rooij1, F J Zwartkruis, M H Verheijen
1Laboratory for Physiological Chemistry and Centre for Biomedical Genetics, Utrecht University, The Netherlands.
Nature
|December 16, 1998
まとめ
研究者らは,循環型AMP (cAMP) によって直接活性化される新しいタンパク質であるEpacを発見しました. このグアニン・ヌクレオチド交換因子 (GEF) は,タンパク質キナーゼAとは独立してRap1の活性を調節し,新しいcAMPシグナル伝達経路を明らかにする.
科学分野:
- 分子生物学は分子生物学である.
- 細胞シグナル伝達 細胞信号伝達
背景:
- RasのようなGTPaseであるRap1は,細胞の増殖,分化,活性化に役割を果たしています.
- Rap1の活性化は,ダイアシルグリセロール,カルシウム,サイクルAMP (cAMP) などのセカンドメッセンジャーによって引き起こされます.
- 以前の理解では,cAMPがRap1を間接的に,潜在的にタンパク質キナーゼAを介して活性化することを示唆していました.
研究 の 目的:
- cAMPによるRap1活性化のメカニズムを調査する.
- cAMP媒介のRap1シグナル伝達に関与する新しいタンパク質を特定する.
- 新しいcAMPで活性化されたグアニン・ヌクレオチド交換因子 (GEF) を特徴づける.
主な方法:
- 新しいcAMP結合タンパク質の遺伝子をクローン化.
- GEFの活性性を評価するためのインビトロおよびインビボアッセイ.
- cAMP誘発のRap1活性化におけるタンパク質キナーゼAの役割を調査する.
主要な成果:
- 新型GEFであるEpac (cAMPによって直接活性化される交換タンパク質) を特定し,クローン化しました.
- Epacは,cAMPと直接結合し,Rap1.1に対するGEF活動を示しています.
- cAMPは,タンパク質キナーゼAから独立して,Rap1に対するEpacのGEF活性を強く誘導する.
結論:
- Epacは,Rap1のCAMPによる直接規制のGEFです.
- Epacは,cAMPのための新しいシグナル伝達経路を表しています.
- Epacは,Rap1の活性化を媒介する,cAMPのための新しい標的タンパク質です.
関連する概念動画
GTPases and their Regulation
Guanine nucleotide-binding proteins (G-proteins), also known as GTPases, are a superfamily of proteins that regulate many cellular processes, such as cell signaling, vesicular transport, and the regulation of cell shape and motility. Mutation or dysfunction of these proteins can lead to disease. There are around 40,000 known G-proteins that can broadly be classified into two groups ‒ small G-proteins consisting of a single domain and large multi-domain G-proteins.
Large G-proteins, also known...
Large G-proteins, also known...
GTPases and their Regulation
Guanine nucleotide-binding proteins (G-proteins), also known as GTPases, are a superfamily of proteins that regulate many cellular processes, such as cell signaling, vesicular transport, and the regulation of cell shape and motility. Mutation or dysfunction of these proteins can lead to disease. There are around 40,000 known G-proteins that can broadly be classified into two groups ‒ small G-proteins consisting of a single domain and large multi-domain G-proteins.
Large G-proteins, also known...
Large G-proteins, also known...
Small GTPases - Ras and Rho
Ras and Rho are small monomeric GTPases that act downstream of receptor tyrosine kinase (RTK) and regulate various cellular processes. These GTPases switch between active and inactive states by binding to guanine nucleotides.
Three regulatory proteins control their activity:
Three regulatory proteins control their activity:
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...
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...
cAMP-dependent Protein Kinase Pathways
Cyclic Adenosine Monophosphate (cAMP) is an essential second messenger that activates protein kinase A (PKA) and regulates various biological processes. A single epinephrine molecule binds to GPCR and activates several heterotrimeric G proteins, each stimulating multiple adenylyl cyclase, amplifying the signal, and synthesizing large numbers of cAMP molecules. Small changes in cAMP concentration affect PKA activity. The binding of four cAMP molecules induces a conformational change in PKA,...


