メラノプシン網膜のギャングリアン細胞による光子捕捉と信号伝達
Michael Tri H Do1, Shin H Kang, Tian Xue
1Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA. mdo@jhmi.edu
Nature
|January 2, 2009
まとめ
本質的に光に敏感な網膜のギャングリア細胞は,メラノプシンを使用して光を検出します. pigmentの密度が低いにもかかわらず,それらは単一の光子に信号を送り,瞳孔の光の反射のような非画像形成視力を駆動します.
科学分野:
- 神経科学は神経科学である.
- 写真生物学 写真生物学
- オフタルモロジック (眼科)
背景:
- 網膜のギャングリオン細胞 (RGCs) のサブセットは,メラノプシンによる固有の光敏感性を持っています.
- これらのメラノプシン発現するRGCは,日中リズムや瞳孔の光の反射を含む,画像を形成しない視覚機能に不可欠です.
- これらの細胞が光信号を変換し,アクションポテンシャルを生成する正確なメカニズムは,まだ完全に理解されていません.
研究 の 目的:
- メラノプシン発現RGCにおける内在光反応の基本的パラメータを解明する.
- メラノプシン光伝導に関連するスパイク生成メカニズムを特徴付ける.
- これらの細胞の光吸収に対する感受性と,行動反応を誘導する役割の決定.
主な方法:
- 網膜のギャングリアン細胞からの電気生理学的記録.
- メラノプシン・ピグメント密度の光度測定.
- シングルフォトン反応と光に誘発されたスパイク生成の分析.
主要な成果:
- これらのRGCにおけるメラノプシン密度は,ロッドとコーンピグメントよりも (10^4倍) 顕著に低く,より明るい光下での機能を示しています.
- フォトンの捕獲量が少ないにもかかわらず,吸収された各フォトンは,ユニークな波形を持つ大きく,例外的に長時間の応答を誘発します.
- これらの細胞は,ロッドに似た単光子の感受性を発揮し,最小限の光曝露で瞳孔の光反射を駆動することができます.
結論:
- メラノプシン発現RGCは,単光子の検出を可能にする非常に敏感な光受容体である.
- 独特の反応動態と感度により,画像を形成しない視覚機能の有効なシグナル伝達が可能になります.
- これらの発見は,光に対する行動的反応を誘導するメラノプシンの光伝達作用を明確にします.
関連する概念動画
Photoreceptors and Visual Pathways
At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...
The Retina
The retina is a layer of nervous tissue at the back of the eye that transduces light into neural signals. This process, called phototransduction, is carried out by rod and cone photoreceptor cells in the back of the retina.
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,...
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,...
Anatomy of the Eyeball
The eye is a spherical, hollow structure composed of three tissue layers. The outer layer — the fibrous tunic, comprises the sclera — a white structure — and the cornea, which is transparent. The sclera encompasses some of the ocular surface, most of which is not visible. However, the 'white of the eye' is distinctively visible in humans compared to other species. The cornea, a clear covering at the front of the eye, enables light penetration. The eye's middle layer, the vascular tunic,...
Vision
Vision is the result of light being detected and transduced into neural signals by the retina of the eye. This information is then further analyzed and interpreted by the brain. First, light enters the front of the eye and is focused by the cornea and lens onto the retina—a thin sheet of neural tissue lining the back of the eye. Because of refraction through the convex lens of the eye, images are projected onto the retina upside-down and reversed.


