Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/06/03 11:01:59」(JST)

wiki en

Neuron A (transmitting) to neuron B (receiving)
1. Mitochondrion
2. Synaptic vesicle with neurotransmitters
3. Autoreceptor
4. Synapse with neurotransmitter released (serotonin)
5. Postsynaptic receptors activated by neurotransmitter (induction of a postsynaptic potential)
6. Calcium channel
7. Exocytosis of a vesicle

8. Recaptured neurotransmitter

Exocytosis (/ˌɛksoʊsaɪˈtoʊsᵻs/^[1]^[2]) is a form of active transport in which a cell transports molecules (such as proteins) out of the cell (exo- + cytosis) by expelling them in an energy-using process. Exocytosis and its counterpart, endocytosis, are used by all cells because most chemical substances important to them are large polar molecules that cannot pass through the hydrophobic portion of the cell membrane by passive means.

In exocytosis, membrane-bound secretory vesicles are carried to the cell membrane, and their contents (water-soluble molecules such as proteins) are secreted into the extracellular environment. This secretion is possible because the vesicle transiently fuses with the outer cell membrane.

Exocytosis is also a mechanism by which cells are able to insert membrane proteins (such as ion channels and cell surface receptors), lipids, and other components into the cell membrane. Vesicles containing these membrane components fully fuse with and become part of the outer cell membrane.

Types

In multicellular organisms there are two types of exocytosis: 1) Ca²⁺ triggered non-constitutive (i.e., regulated exocytosis) and 2) non-Ca²⁺ triggered constitutive. Exocytosis in neuronal chemical synapses is Ca²⁺ triggered and serves interneuronal signalling. Constitutive exocytosis is performed by all cells and serves the release of components of the extracellular matrix, or just delivery of newly synthesized membrane proteins that are incorporated in the plasma membrane after the fusion of the transport vesicle. Regulated exocytosis, on the other hand, requires an external signal, a specific sorting signal on the vesicles, a clathrin coat, as well as an increase in intracellular calcium. Exocytosis is the opposite of endocytosis. 3) Vesicular exocytosis in prokaryote gram negative microbes is the latest finding in exocytosis. Herein, periplasm of gram negative microbes is pinched off as bacterial outer membrane vesicles (OMVs) for translocating microbial biochemical signals into eukaryotic host cells^[3] or other microbes located nearby,^[4] accomplishing control of the secreting microbe on its environment - including invasion of host, endotoxemia, competing with other microbes for nutrition, etc. This finding of membrane vesicle trafficking occurring at the host-pathogen interface, also breaks the myth that exo-cytosis is purely a eukaryotic cell phenomenon.^[5]

Steps

Five steps are involved in exocytosis:

Vesicle trafficking

Certain vesicle-trafficking steps require the transportation of a vesicle over a moderately small distance. For example, vesicles that transport proteins from the Golgi apparatus to the cell surface area, will be likely to use motor proteins and a cytoskeletal track to get closer to their target. Before tethering would have been appropriate, many of the proteins used for the active transport would have been instead set for passive transport, because the Golgi apparatus does not require ATP to transport proteins. Both the actin- and the microtubule-base are implicated in these processes, along with several motor proteins. Once the vesicles reach their targets, they come into contact with tethering factors that can restrain them.

Vesicle tethering

It is useful to distinguish between the initial, loose tethering of vesicles to their objective from the more stable, packing interactions. Tethering involves links over distances of more than about half the diameter of a vesicle from a given membrane surface (>25 nm). Tethering interactions are likely to be involved in concentrating synaptic vesicles at the synapse.

Tethered vesicles are also involved in regular cell's transcription processes.

Vesicle docking

Secretory vesicles transiently dock at the cell plasma membrane, preceding the formation of a tight t-/v-SNARE complex, leading to priming and the establishment of continuity between the opposing bilayers.

Vesicle priming

In neuronal exocytosis, the term priming has been used to include all of the molecular rearrangements and ATP-dependent protein and lipid modifications that take place after initial docking of a synaptic vesicle but before exocytosis, such that the influx of calcium ions is all that is needed to trigger nearly instantaneous neurotransmitter release. In other cell types, whose secretion is constitutive (i.e. continuous, calcium ion independent, non-triggered) there is no priming.

Vesicle fusion

Transient vesicle fusion is driven by SNARE proteins, resulting in release of vesicle contents into the extracellular space (or in case of neurons in the synaptic cleft).

The merging of the donor and the acceptor membranes accomplishes three tasks:

The surface of the plasma membrane increases (by the surface of the fused vesicle). This is important for the regulation of cell size, e.g., during cell growth.
The substances within the vesicle are released into the exterior. These might be waste products or toxins, or signaling molecules like hormones or neurotransmitters during synaptic transmission.
Proteins embedded in the vesicle membrane are now part of the plasma membrane. The side of the protein that was facing the inside of the vesicle now faces the outside of the cell. This mechanism is important for the regulation of transmembrane and transporters.

Vesicle Retrieval

Retrieval of synaptic vesicles occurs by endocytosis. Some synaptic vesicles are recycled without a full fusion into the membrane (kiss-and-run fusion), while others require a complete reformation of synaptic vesicles from the membrane by a specialized complex of proteins (clathrin). Non-constitutive exocytosis and subsequent endocytosis are highly energy expending processes, and thus, are dependent on mitochondria.^[6]

Examination of cells following secretion using electron microscopy demonstrate increased presence of partially empty vesicles following secretion. This suggested that during the secretory process, only a portion of the vesicular content is able to exit the cell. This could only be possible if the vesicle were to temporarily establish continuity with the cell plasma membrane, expel a portion of its contents, then detach, reseal, and withdraw into the cytosol (endocytose). In this way, the secretory vesicle could be reused for subsequent rounds of exo-endocytosis, until completely empty of its contents.^[7]

References

^ "Exocytosis". Oxford Dictionaries. Oxford University Press. Retrieved 2016-01-21.
^ "Exocytosis". Merriam-Webster Dictionary. Retrieved 2016-01-21.
^ YashRoy R C (1993) Eelectron microscope studies of surface pili and vesicles of Salmonella 3,10:r:- organisms. Indian Journal of Animal Sciences, vol. 63, pp. 99-102.https://www.researchgate.net/publication/230817087_Electron_microscope_studies_of_surface_pilli_and_vesicles_of_Salmonella_310r-_organisms?ev=prf_pub
^ Kadurugamuwa, J L; Beveridge, T J (1996). "Bacteriolytic effect of membrane vesicles from Pseudomonas aeruginosa on other bacterial including pathogens: conceptually new antibiotics". Journal of Bacteriology 178 (10): 2767–2774. PMC 178010. PMID 8631663.
^ YashRoy, R.C. (1998). "Discovery of vesicular exocytosis in procaryotes and its role in Salmonella invasion" (PDF). Current Science 75 (10): 1062–1066.
^ Ivannikov, M.; et al. (2013). "Synaptic vesicle exocytosis in hippocampal synaptosomes correlates directly with total mitochondrial volume". J. Mol. Neurosci. 49 (1): 223–230. doi:10.1007/s12031-012-9848-8. PMID 22772899.
^ Boron, WF & Boulpaep, EL (2012), Medical Physiology. A Cellular and Molecular Approach 2, Philadelphia: Elsevier

External links

Exocytosis at the US National Library of Medicine Medical Subject Headings (MeSH)

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 皮膚の異型リンパ球浸潤と診断された患者に対するアプローチ approach to the patient with a diagnosis of atypical lymphocytic infiltrate of the skin
2. 乳汁分泌の生理学 physiology of lactation
3. 色素性紫斑（毛細血管炎） pigmented purpuric dermatoses capillaritis
4. 多形紅斑の病因、臨床的特徴、および診断 pathogenesis clinical features and diagnosis of erythema multiforme
5. 胎盤の発達および生理学 placental development and physiology

English Journal

Endosomal trafficking of open Major Histocompatibility Class I conformers--implications for presentation of endocytosed antigens.

Mahmutefendić H, Zagorac GB, Tomaš MI, Groettrup M, Momburg F, Lučin P.SourceUniversity of Rijeka, Faculty of Medicine, Department of Physiology and Immunology, Rijeka, Croatia.
Molecular immunology.Mol Immunol.2013 Sep;55(2):149-52. doi: 10.1016/j.molimm.2012.10.008. Epub 2012 Nov 27.
Major Histocompatibility Class I (MHC-I) molecules are present at the cell surface either as fully conformed trimolecular complexes composed of heavy chain, beta-2-microglobulin (β2m) and antigenic peptide or as various open forms, devoid of the peptide and/or β2m. While the role of fully conforme
PMID 23200229

The effect of hydrophilic and hydrophobic structure of amphiphilic polymeric micelles on their transport in epithelial MDCK cells.

Yu C, He B, Xiong MH, Zhang H, Yuan L, Ma L, Dai WB, Wang J, Wang XL, Wang XQ, Zhang Q.SourceThe State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China.
Biomaterials.Biomaterials.2013 Aug;34(26):6284-98. doi: 10.1016/j.biomaterials.2013.05.006. Epub 2013 May 25.
The interaction of nanocarriers with cells including their transcellular behavior is vital not only for a drug delivery system, but also for the safety of nanomaterials. In an attempt to clarify how the structures of polymers impact the transport mechanisms of their nanocarriers in epithelial cells,
PMID 23714243

The transport mechanisms of polymer nanoparticles in Caco-2 epithelial cells.

He B, Lin P, Jia Z, Du W, Qu W, Yuan L, Dai W, Zhang H, Wang X, Wang J, Zhang X, Zhang Q.SourceState Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China.
Biomaterials.Biomaterials.2013 Aug;34(25):6082-98. doi: 10.1016/j.biomaterials.2013.04.053. Epub 2013 May 18.
As the primary physiological barrier, intestinal epithelial cells regulate the transportation of oral therapeutic agents including nanomedicines which significantly improves the bioavailability of many drugs. However, currently there seems in the lack of comprehensive understanding on nanoparticle t
PMID 23694903

Japanese Journal

高頻度シナプス伝達を支えるシナプス小胞エンドサイトーシス制御機構

江口工学,高橋智幸
生物物理 54(1), 015-018, 2014
… During synaptic transmission, exocytosis and endocytosis of synaptic vesicles must be balanced for maintaining the number of releasable vesicles. … We found that protein kinase G (PKG) plays this balancing role at the calyx of Held presynaptic terminals when glutamate is massively released by exocytosis. …
NAID 130003391394

Resveratrol Improves the Mitochondrial Function and Fertilization Outcome of Bovine Oocytes

TAKEO Shun,SATO Daichi,KIMURA Koji,MONJI Yasunori,KUWAYAMA Takehito,KAWAHARA-MIKI Ryoka,IWATA Hisataka
Journal of Reproduction and Development 60(2), 92-99, 2014
… In Exp 4, Res-induced zona hardening improved the distribution and exocytosis of cortical granules after in vitro fertilization. …
NAID 130003381865

細胞質顆粒の放出機序

堀内久徳
臨床免疫・アレルギー科 60(2), 228-232, 2013-08
NAID 40019789531

Related Pictures

★リンクテーブル★

リンク元	「開口放出」「exocytic」「emiocytosis」「exocytotic」「エキソシトシス」

「開口放出」

　　[★]

英: exocytosis
同: 開口分泌、エクソサイトーシス
関

[show details]

エクソサイトーシス : 約 1,290 件
開口分泌 : 約 3,320 件
開口放出 : 約 5,700 件

細胞外への分泌形態の一つ

様式

1. 分泌顆粒は細胞内線維群の働きによって細胞質内を移動し、細胞膜へと接近
2. 分泌顆粒膜外層が細胞膜内層と、分泌顆粒膜内層が細胞膜外層と融合
3. 分泌顆粒内腔が細胞外界と連絡し、顆粒内容物は細胞外へと遊出
4. 細胞膜と融合した顆粒膜は、そのまま新たな細胞膜となるか、細胞内へ再び戻る

参考

-exocytosis

-エクソサイトーシス

「exocytic」

　　[★]

開口放出の、開口分泌の、細胞外への

関: emiocytosis、exocytosis、exocytotic、extracellular、extracellularly

「emiocytosis」

　　[★]

吐出作用、開口放出、エミオサイトーシス

関: exocytic、exocytosis、exocytotic

「exocytotic」

　　[★]

開口分泌の、開口放出の

関: emiocytosis、exocytic、exocytosis

「エキソシトシス」

　　[★]

英: exocytosis
関: エキソサイトーシス、開口分泌、開口放出

[1] "Exocytosis". Oxford Dictionaries. Oxford University Press. Retrieved 2016-01-21.

[2] "Exocytosis". Merriam-Webster Dictionary. Retrieved 2016-01-21.

[3] YashRoy R C (1993) Eelectron microscope studies of surface pili and vesicles of Salmonella 3,10:r:- organisms. Indian Journal of Animal Sciences, vol. 63, pp. 99-102.https://www.researchgate.net/publication/230817087_Electron_microscope_studies_of_surface_pilli_and_vesicles_of_Salmonella_310r-_organisms?ev=prf_pub

[4] Kadurugamuwa, J L; Beveridge, T J (1996). "Bacteriolytic effect of membrane vesicles from Pseudomonas aeruginosa on other bacterial including pathogens: conceptually new antibiotics". Journal of Bacteriology 178 (10): 2767–2774. PMC 178010. PMID 8631663.

[5] YashRoy, R.C. (1998). "Discovery of vesicular exocytosis in procaryotes and its role in Salmonella invasion" (PDF). Current Science 75 (10): 1062–1066.

[6] Ivannikov, M.; et al. (2013). "Synaptic vesicle exocytosis in hippocampal synaptosomes correlates directly with total mitochondrial volume". J. Mol. Neurosci. 49 (1): 223–230. doi:10.1007/s12031-012-9848-8. PMID 22772899.

[7] Boron, WF & Boulpaep, EL (2012), Medical Physiology. A Cellular and Molecular Approach 2, Philadelphia: Elsevier

匿名

検索

案内

案内

exocytosis