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The cell biology of vision.

Sung CH, Chuang JZ - J. Cell Biol. (2010)

Bottom Line: Humans possess the remarkable ability to perceive color, shape, and motion, and to differentiate between light intensities varied by over nine orders of magnitude.Phototransduction--the process in which absorbed photons are converted into electrical responses--is the first stage of visual processing, and occurs in the outer segment, the light-sensing organelle of the photoreceptor cell.Studies of genes linked to human inherited blindness have been crucial to understanding the biogenesis of the outer segment and membrane-trafficking of photoreceptors.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065, USA. chsung@med.cornell.edu

ABSTRACT
Humans possess the remarkable ability to perceive color, shape, and motion, and to differentiate between light intensities varied by over nine orders of magnitude. Phototransduction--the process in which absorbed photons are converted into electrical responses--is the first stage of visual processing, and occurs in the outer segment, the light-sensing organelle of the photoreceptor cell. Studies of genes linked to human inherited blindness have been crucial to understanding the biogenesis of the outer segment and membrane-trafficking of photoreceptors.

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The morphological and molecular characteristics of vertebrate rod. (A) 3D cartoons depict the inter-relationship between rod and RPE (left) and IS–OS junction (right); RPE apical microvilli interdigitate the distal half of the OS. R, RPE; V, microvilli; O, OS; I, IS; N, nucleus, S, synaptic terminal. (B) A schematic drawing of a mammalian rod depicting its ciliary stalk and microtubule organizations; the axonemal (Ax) and cytoplasmic microtubules (not depicted) are anchored at the basal body in the distal IS. CP, calycal process; BB, basal body. The interactions between opposing membranes are depicted in color. The yellow shade indicates that the putative interaction of the ectodomains of usherin–VLGR1–whirlin complexes appear on both CC plasmalemma and the lateral plasmalemma of the IS ridge complex. The green shade indicates the putative chlosterol–prominin-1–protocadherin 21 interaction. (C) Electron micrographs reveal the hairpin loop structures of the disc rims and the fibrous links across the gap between the disc rims and plasma membranes (arrowheads). Bar, 100 nm. Reproduced from Townes-Anderson et al. (1988) with permission from J. Neurosci. (D) The OS plasma membrane and disc membrane have distinctive protein compositions; molecules are either expressed on the plasma membrane or the disc membranes, but not both. The only exception is rhodopsin; rhodopsin is present on disc membrane (with a much higher concentration) and plasma membrane (not depicted). The cGMP-gated channel: Na/Ca-K exchanger complex on the plasma membrane directly binds to the peripherin-2–ROM-1 oligomeric complex on the disc rim. The cGMP-gated channel is composed of three A1 subunits and one B1 subunit. ABCA4, a protein involved in retinoid cycle, is also enriched on the disc rim. RetGC1, retinal guanylyl cyclase; CNG channel, cGMP-gated channel. Adapted from Molday (2004). (E) Electron micrograph showing the longitudinal sectioning view of IS–OS junction of rat rod. Arrows point to the CC axonemal vesicles. An open arrow points to the fibrous structures linking the opposing membranes. Bar, 50 nm. Inset: a transverse section through the CC shows 9+0 arrangement; an arrow points to the cross-linker that gaps the microtubule doublet and adjacent ciliary membrane. R, apical IS ridge. Bar,100 nm. (F) Electron micrographs of a low-power (inset) and high-power images of the rat retina, at the junction between the rod OS and the RPE. MV, RPE microvillar processes enwrapped the distal OS. A white arrow points to a group of saccules from the tip of OS curls and upwards. White arrows in inset point to two distal OS fragments that are engulfed by RPE. Bar, 500 nm. Inset modified from Chuang et al. (2010) with permission from Mol. Biol. Cell.
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fig2: The morphological and molecular characteristics of vertebrate rod. (A) 3D cartoons depict the inter-relationship between rod and RPE (left) and IS–OS junction (right); RPE apical microvilli interdigitate the distal half of the OS. R, RPE; V, microvilli; O, OS; I, IS; N, nucleus, S, synaptic terminal. (B) A schematic drawing of a mammalian rod depicting its ciliary stalk and microtubule organizations; the axonemal (Ax) and cytoplasmic microtubules (not depicted) are anchored at the basal body in the distal IS. CP, calycal process; BB, basal body. The interactions between opposing membranes are depicted in color. The yellow shade indicates that the putative interaction of the ectodomains of usherin–VLGR1–whirlin complexes appear on both CC plasmalemma and the lateral plasmalemma of the IS ridge complex. The green shade indicates the putative chlosterol–prominin-1–protocadherin 21 interaction. (C) Electron micrographs reveal the hairpin loop structures of the disc rims and the fibrous links across the gap between the disc rims and plasma membranes (arrowheads). Bar, 100 nm. Reproduced from Townes-Anderson et al. (1988) with permission from J. Neurosci. (D) The OS plasma membrane and disc membrane have distinctive protein compositions; molecules are either expressed on the plasma membrane or the disc membranes, but not both. The only exception is rhodopsin; rhodopsin is present on disc membrane (with a much higher concentration) and plasma membrane (not depicted). The cGMP-gated channel: Na/Ca-K exchanger complex on the plasma membrane directly binds to the peripherin-2–ROM-1 oligomeric complex on the disc rim. The cGMP-gated channel is composed of three A1 subunits and one B1 subunit. ABCA4, a protein involved in retinoid cycle, is also enriched on the disc rim. RetGC1, retinal guanylyl cyclase; CNG channel, cGMP-gated channel. Adapted from Molday (2004). (E) Electron micrograph showing the longitudinal sectioning view of IS–OS junction of rat rod. Arrows point to the CC axonemal vesicles. An open arrow points to the fibrous structures linking the opposing membranes. Bar, 50 nm. Inset: a transverse section through the CC shows 9+0 arrangement; an arrow points to the cross-linker that gaps the microtubule doublet and adjacent ciliary membrane. R, apical IS ridge. Bar,100 nm. (F) Electron micrographs of a low-power (inset) and high-power images of the rat retina, at the junction between the rod OS and the RPE. MV, RPE microvillar processes enwrapped the distal OS. A white arrow points to a group of saccules from the tip of OS curls and upwards. White arrows in inset point to two distal OS fragments that are engulfed by RPE. Bar, 500 nm. Inset modified from Chuang et al. (2010) with permission from Mol. Biol. Cell.

Mentions: Phototransduction. Phototransduction occurs in the outer segments (OS) of photoreceptors. Light initiates the isomerization of the 11-cis retinal, a chromophore covalently conjugated to rhodopsin embedded within the disc membranes. Photoactivated rhodopsin activates the heterotrimeric G protein transducin by catalyzing the exchange of GDP for GTP. The dissociated α-subunit of transducin then activates cGMP-phosphodiesterase, which rapidly hydrolyzes cytoplasmic cGMP. The decrease in cGMP concentration causes closure of cGMP-gated cation channels on the plasma membrane (Fig. 2 D). As a result, the cells are hyperpolarized and release less glutamate transmitters to their connected bipolar cells.


The cell biology of vision.

Sung CH, Chuang JZ - J. Cell Biol. (2010)

The morphological and molecular characteristics of vertebrate rod. (A) 3D cartoons depict the inter-relationship between rod and RPE (left) and IS–OS junction (right); RPE apical microvilli interdigitate the distal half of the OS. R, RPE; V, microvilli; O, OS; I, IS; N, nucleus, S, synaptic terminal. (B) A schematic drawing of a mammalian rod depicting its ciliary stalk and microtubule organizations; the axonemal (Ax) and cytoplasmic microtubules (not depicted) are anchored at the basal body in the distal IS. CP, calycal process; BB, basal body. The interactions between opposing membranes are depicted in color. The yellow shade indicates that the putative interaction of the ectodomains of usherin–VLGR1–whirlin complexes appear on both CC plasmalemma and the lateral plasmalemma of the IS ridge complex. The green shade indicates the putative chlosterol–prominin-1–protocadherin 21 interaction. (C) Electron micrographs reveal the hairpin loop structures of the disc rims and the fibrous links across the gap between the disc rims and plasma membranes (arrowheads). Bar, 100 nm. Reproduced from Townes-Anderson et al. (1988) with permission from J. Neurosci. (D) The OS plasma membrane and disc membrane have distinctive protein compositions; molecules are either expressed on the plasma membrane or the disc membranes, but not both. The only exception is rhodopsin; rhodopsin is present on disc membrane (with a much higher concentration) and plasma membrane (not depicted). The cGMP-gated channel: Na/Ca-K exchanger complex on the plasma membrane directly binds to the peripherin-2–ROM-1 oligomeric complex on the disc rim. The cGMP-gated channel is composed of three A1 subunits and one B1 subunit. ABCA4, a protein involved in retinoid cycle, is also enriched on the disc rim. RetGC1, retinal guanylyl cyclase; CNG channel, cGMP-gated channel. Adapted from Molday (2004). (E) Electron micrograph showing the longitudinal sectioning view of IS–OS junction of rat rod. Arrows point to the CC axonemal vesicles. An open arrow points to the fibrous structures linking the opposing membranes. Bar, 50 nm. Inset: a transverse section through the CC shows 9+0 arrangement; an arrow points to the cross-linker that gaps the microtubule doublet and adjacent ciliary membrane. R, apical IS ridge. Bar,100 nm. (F) Electron micrographs of a low-power (inset) and high-power images of the rat retina, at the junction between the rod OS and the RPE. MV, RPE microvillar processes enwrapped the distal OS. A white arrow points to a group of saccules from the tip of OS curls and upwards. White arrows in inset point to two distal OS fragments that are engulfed by RPE. Bar, 500 nm. Inset modified from Chuang et al. (2010) with permission from Mol. Biol. Cell.
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Related In: Results  -  Collection

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fig2: The morphological and molecular characteristics of vertebrate rod. (A) 3D cartoons depict the inter-relationship between rod and RPE (left) and IS–OS junction (right); RPE apical microvilli interdigitate the distal half of the OS. R, RPE; V, microvilli; O, OS; I, IS; N, nucleus, S, synaptic terminal. (B) A schematic drawing of a mammalian rod depicting its ciliary stalk and microtubule organizations; the axonemal (Ax) and cytoplasmic microtubules (not depicted) are anchored at the basal body in the distal IS. CP, calycal process; BB, basal body. The interactions between opposing membranes are depicted in color. The yellow shade indicates that the putative interaction of the ectodomains of usherin–VLGR1–whirlin complexes appear on both CC plasmalemma and the lateral plasmalemma of the IS ridge complex. The green shade indicates the putative chlosterol–prominin-1–protocadherin 21 interaction. (C) Electron micrographs reveal the hairpin loop structures of the disc rims and the fibrous links across the gap between the disc rims and plasma membranes (arrowheads). Bar, 100 nm. Reproduced from Townes-Anderson et al. (1988) with permission from J. Neurosci. (D) The OS plasma membrane and disc membrane have distinctive protein compositions; molecules are either expressed on the plasma membrane or the disc membranes, but not both. The only exception is rhodopsin; rhodopsin is present on disc membrane (with a much higher concentration) and plasma membrane (not depicted). The cGMP-gated channel: Na/Ca-K exchanger complex on the plasma membrane directly binds to the peripherin-2–ROM-1 oligomeric complex on the disc rim. The cGMP-gated channel is composed of three A1 subunits and one B1 subunit. ABCA4, a protein involved in retinoid cycle, is also enriched on the disc rim. RetGC1, retinal guanylyl cyclase; CNG channel, cGMP-gated channel. Adapted from Molday (2004). (E) Electron micrograph showing the longitudinal sectioning view of IS–OS junction of rat rod. Arrows point to the CC axonemal vesicles. An open arrow points to the fibrous structures linking the opposing membranes. Bar, 50 nm. Inset: a transverse section through the CC shows 9+0 arrangement; an arrow points to the cross-linker that gaps the microtubule doublet and adjacent ciliary membrane. R, apical IS ridge. Bar,100 nm. (F) Electron micrographs of a low-power (inset) and high-power images of the rat retina, at the junction between the rod OS and the RPE. MV, RPE microvillar processes enwrapped the distal OS. A white arrow points to a group of saccules from the tip of OS curls and upwards. White arrows in inset point to two distal OS fragments that are engulfed by RPE. Bar, 500 nm. Inset modified from Chuang et al. (2010) with permission from Mol. Biol. Cell.
Mentions: Phototransduction. Phototransduction occurs in the outer segments (OS) of photoreceptors. Light initiates the isomerization of the 11-cis retinal, a chromophore covalently conjugated to rhodopsin embedded within the disc membranes. Photoactivated rhodopsin activates the heterotrimeric G protein transducin by catalyzing the exchange of GDP for GTP. The dissociated α-subunit of transducin then activates cGMP-phosphodiesterase, which rapidly hydrolyzes cytoplasmic cGMP. The decrease in cGMP concentration causes closure of cGMP-gated cation channels on the plasma membrane (Fig. 2 D). As a result, the cells are hyperpolarized and release less glutamate transmitters to their connected bipolar cells.

Bottom Line: Humans possess the remarkable ability to perceive color, shape, and motion, and to differentiate between light intensities varied by over nine orders of magnitude.Phototransduction--the process in which absorbed photons are converted into electrical responses--is the first stage of visual processing, and occurs in the outer segment, the light-sensing organelle of the photoreceptor cell.Studies of genes linked to human inherited blindness have been crucial to understanding the biogenesis of the outer segment and membrane-trafficking of photoreceptors.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065, USA. chsung@med.cornell.edu

ABSTRACT
Humans possess the remarkable ability to perceive color, shape, and motion, and to differentiate between light intensities varied by over nine orders of magnitude. Phototransduction--the process in which absorbed photons are converted into electrical responses--is the first stage of visual processing, and occurs in the outer segment, the light-sensing organelle of the photoreceptor cell. Studies of genes linked to human inherited blindness have been crucial to understanding the biogenesis of the outer segment and membrane-trafficking of photoreceptors.

Show MeSH
Related in: MedlinePlus