味覚受容体細胞での変換には,cAMPに依存したタンパク質キナーゼが必要です
P Avenet1, F Hofmann, B Lindemann
1Physiology II, Universität des Saarlandes, Homburg, FRG.
Nature
|January 28, 1988
まとめ
サイクルアデノシンモノフォスファート (cAMP) は,タンパク質キナーゼを活性化することによって,味覚細胞の去極化を引き起こす. このキナーゼは,他の感覚細胞と異なる特定のカリウムチャネルを無効化する.
科学分野:
- 神経科学は神経科学である.
- 細胞生物学 細胞生物学
- 感覚生理学 感覚生理学とは
背景:
- サイクルアデノシンモノフォスファート (cAMP) は,味覚化学受容における細胞内伝達物質である.
- 甘い味の受容体細胞は,甘い刺激に反応してcAMPを生成する.
- 味覚受容体細胞膜にcAMPが作用するメカニズムは完全に理解されていません.
研究 の 目的:
- cAMPが味覚受容体細胞の脱極化を引き起こすメカニズムを調査する.
- cAMP媒介の味覚シグナル伝達に関与する特定のイオンチャンネルとシグナル伝達経路の特定.
主な方法:
- 味覚受容体細胞からの全細胞パッチクランプの記録.
- インサイド・アウトの膜パッチ実験.
- イオンチャネル活動の電気生理学的分析.
主要な成果:
- cAMPは,味覚受容体細胞の重要な脱極化を引き起こします.
- この脱極化は,cAMP依存タンパク質キナーゼによって媒介されます.
- タンパク質キナーゼは,主に 44 pS の伝導性を有するカリウムチャネルを無効化する.
結論:
- 味覚の細胞内信号伝達は,嗅覚と光受容体の信号伝達とは異なる.
- 味覚細胞におけるcAMPは,直接結合ではなく,イオンチャネルのリン酸化によって作用する.
- このリン酸化機構は,カリウムチャネル活性と味覚細胞の興奮性を調節する.
関連する概念動画
Amplifying Signals via Second Messengers
Many receptor binding ligands are hydrophilic; they do not cross the cell membrane but bind to cell-surface receptors. Thus, their message must be relayed by second messengers present in the cell cytoplasm. There are several second messenger pathways, each with its own way of relaying information. For example, the G protein-coupled receptors can activate both phosphoinositol and cyclic AMP (cAMP) second messenger pathways. The phosphoinositol pathway is active when the receptor induces...
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...
MAPK Signaling Cascades
Mitogen-activated protein kinase, or MAPK pathway, activates three sequential kinases to regulate cellular responses such as proliferation, differentiation, survival, and apoptosis. The canonical MAPK pathway starts with a mitogen or growth factor binding to an RTK. The activated RTKs stimulate Ras, which recruits Raf or MAP3 Kinase (MAPKKK), the first kinase of the MAPK signaling cascade. Raf further phosphorylates and activates MEK or MAP2 Kinases (MAPKK), which in turn phosphorylates MAP...
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,...
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,...
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,...


