WordNet

of or belonging to neither the right nor the left politically or intellectually
a building dedicated to a particular activity; "they were raising money to build a new center for research" (同)centre
(American football) the position of the player on the line of scrimmage who puts the ball in play; "it is a centers responsibility to get the football to the quarterback"
a position on a basketball team of the player who participates in the jump that starts the game
the position on a hockey team of the player who participates in the face off at the beginning of the game
a place where some particular activity is concentrated; "they received messages from several centers" (同)centre
the sweet central portion of a piece of candy that is enclosed in chocolate or some other covering (同)centre
the object upon which interest and attention focuses; "his stories made him the center of the party" (同)centre, center of attention, centre of attention
an area that is approximately central within some larger region; "it is in the center of town"; "they ran forward into the heart of the struggle"; "they were in the eye of the storm" (同)centre, middle, heart, eye
a point equidistant from the ends of a line or the extremities of a figure (同)centre, midpoint
a cluster of nerve cells governing a specific bodily process; "in most people the speech center is in the left hemisphere" (同)centre, nerve_center, nerve centre
(football) the person who plays center on the line of scrimmage and snaps the ball to the quarterback; "the center fumbled the handoff" (同)snapper
(basketball) the person who plays center on a basketball team
(ice hockey) the person who plays center on a hockey team
politically moderate persons; centrists
the middle of a military or naval formation; "they had to reinforce the center"
move into the center; "That vase in the picture is not centered" (同)centre
equally distant from the extremes (同)halfway, middle, midway
a fractional monetary unit of several countries
(American football) putting the ball in play by passing it (between the legs) to a back; "the quarterback fumbled the snap" (同)snap
being or placed in the center
a microscopically small tubule

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/11/23 17:09:41」(JST)

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The microtubule-organizing center (MTOC) is a structure found in eukaryotic cells from which microtubules emerge. MTOCs have two main functions: the organization of eukaryotic flagella and cilia and the organization of the mitotic and meiotic spindle apparatus, which separate the chromosomes during cell division. The MTOC is a major site of microtubule nucleation and can be visualized in cells by immunohistochemical detection of γ-tubulin. The morphological characteristics of MTOCs vary between the different phylas and kingdoms.^[1] In animals, the two most important types of MTOCs are the basal bodies associated with cilia and the centrosome associated with spindle formation.

Organization of MTOC in cells

Microtubule-organizing centers function as the site where microtubule formation begin, as well as a location where free-ends of microtubules attract to.^[2] Within the cells, microtubule-organizing centers can take on many different forms. An array of microtubules can arrange themselves in a pinwheel structure to form the basal bodies, which can lead to the formation of microtubule arrays in the cytoplasm or the 9+2 axoneme. Other arrangements range from fungi spindle pole bodies to the eukaryotic chromosal kinetochores (flat, laminated plaques). MTOCs can be freely dispersed throughout the cytoplasm or centrally localized as foci. The most notable MTOCs are the centrosome at interphase and the mitotic spindle poles.

Centrioles can act as markers for MTOCs in the cell.^[3] If they are freely distributed in the cytoplasm, centrioles can gather during differentiation to become MTOCs. They can also be focused around a centrosome as a single MTOC, though centrosomes can work as an MTOC absent of centrioles.

Interphase MTOC

Most animal cells have one MTOC during interphase, usually located near the nucleus, and generally associated closely with the Golgi apparatus. The MTOC is made up of a pair of centrioles at its center, and is surrounded by pericentriolar material (PCM) that is important for microtubule nucleation. Microtubules are anchored at the MTOC by their minus ends, while their plus ends continue to grow into the cell periphery. The polarity of the microtubules is important for cellular transport, as the motor proteins kinesin and dynein typically move preferentially in either the "plus" or "minus" direction, respectively, along a microtubule, allowing vesicles to be directed to or from the endoplasmic reticulum and Golgi apparatus. Particularly for the Golgi apparatus, structures associated with the apparatus travel towards the minus end of a microtubule and aid in the overall structure and site of the Golgi in the cell.^[4]

Centrosomes

Main article: Centrosomes

Movements of the microtubules are based on the actions of the centrosome.^[5] Each daughter cell after the cessation of mitosis contains one primary MTOC.^[6] Before cell division begins, the interphase MTOC replicates to form two distinct MTOCs (now typically referred to as centrosomes). During cell division, these centrosomes move to opposite ends of the cell and nucleate microtubules to help form the mitotic/meiotic spindle. If the MTOC does not replicate, the spindle cannot form, and mitosis ceases prematurely.^[7] Refer to centrosome for more detailed information.

y-tubulin is a protein located at the centrosome that nucleates the microtubules by interacting with the tubulin monomer subunit in the microtubule at the minus end.^[8] Organization of the microtubules at the MTOC, or centrosome in this case, is determined by the polarity of the microtubules defined by y-tubulin.^[9]

Basal body

Main article: Basal body

In epithelial cells, MTOCs also anchor and organize the microtubules that make up cilia. As with the centrosome, these MTOCs stabilize and give direction to the microtubules, in this case to allow unidirectional movement of the cilium itself, rather than vesicles moving along it.

Spindle pole body

Main article: Spindle pole body

In yeasts and some algae, the MTOC is embedded into the nuclear envelope as a spindle pole body. Centrioles do not exist in the MTOCs of yeast and fungi.^[10] In these organisms, the nuclear envelope does not break down during mitosis and the spindle pole body serves to connect cytoplasmic with nuclear microtubules. The disc-shaped spindle pole body is organized into three layers: the central plaque, inner plaque, and outer plaque. The central plaque is embedded in the membrane, while the inner plaque is an amorphous intranuclear layer, and the outer plaque is the layer located in the cytoplasm.^[11]

Plant MTOCs

Plant cells lack centrioles or spindle pole bodies. Instead, the nuclear envelope itself appears to function as the main MTOC for microtubule nucleation and spindle organization during plant cell mitosis.

Signal Tranduction

The MTOC reorients itself during signal transduction, primarily during wound repair or immune responses.^[12] The MTOC is relocalized to a position between the edge of the cell and the nucleus in cells like macrophages, fibroblasts, and endothelial cells. Organelles, such as the Golgi apparatus, aid in the reorientation of the MTOC and can occur rapidly. Transduction signals cause microtubules to grow or contract, as well as the centrosome to become motile. The MTOC is located in a perinuclear position and contains the negative ends of microtubules while the positive ends grow rapidly towards the edge of the cell. The Golgi apparatus reorients along with the MTOC, and together cause the cell to seemingly send a polarized signal.^[13]

In immune responses, upon interaction with a target cell in response to antigen-specific loaded antigen-presenting cells, immune cells, such as the T-Cells, Natural Killer Cells, and cytotoxic t-lymphocytes, localize their MTOCs near the contact zone between the immune cell and the target cell. For T-Cells, the T-Cell receptor signaling response causes the reorientation of the MTOC by microtubules shortening to bring the MTOC to the site of interaction of the T-Cell receptor.^[14]

References

^ Francis, Susan; Trisha Davis (1999). "The spindle pole body of Saccharomyces cerevisiae: Architecture and assembly of the core components". Current Topics in Developmental Biology (Elsevier) 49: 105–132. http://www.sciencedirect.com./science/article/pii/S0070215399490064. Retrieved 04/29/2012.
^ Brinkley, B.R. (1985). "Microtubule Organizing Centers". Annual Reviews: Cell Biology 1: 145–172.
^ Brinkley, B.R. (1985). "Microtubule Organizing Centers". Annual Reviews: Cell Biology 1: 145–172.
^ Kreis, Thomas (1990). "Role of Microtubules in the Organisation of the Golgi Apparatus". Cell Motility and Cytoskeleton 15: 67–70. http://onlinelibrary.wiley.com/doi/10.1002/cm.970150202/pdf. Retrieved 05/02/2012.
^ Francis, Susan; Trisha Davis (1999). "The spindle pole body of Saccharomyces cerevisiae: Architecture and assembly of the core components". Current Topics in Developmental Biology (Elsevier) 49: 105–132. http://www.sciencedirect.com./science/article/pii/S0070215399490064. Retrieved 04/29/2012.
^ Brinkley, B.R. (1985). "Microtubule Organizing Centers". Annual Reviews: Cell Biology 1: 145–172.
^ Francis, Susan; Trisha Davis (1999). "The spindle pole body of Saccharomyces cerevisiae: Architecture and assembly of the core components". Current Topics in Developmental Biology (Elsevier) 49: 105–132. http://www.sciencedirect.com./science/article/pii/S0070215399490064. Retrieved 04/29/2012.
^ Francis, Susan; Trisha Davis (1999). "The spindle pole body of Saccharomyces cerevisiae: Architecture and assembly of the core components". Current Topics in Developmental Biology (Elsevier) 49: 105–132. http://www.sciencedirect.com./science/article/pii/S0070215399490064. Retrieved 04/29/2012.
^ Francis, Susan; Trisha Davis (1999). "The spindle pole body of Saccharomyces cerevisiae: Architecture and assembly of the core components". Current Topics in Developmental Biology (Elsevier) 49: 105–132. http://www.sciencedirect.com./science/article/pii/S0070215399490064. Retrieved 04/29/2012.
^ Francis, Susan; Trisha Davis (1999). "The spindle pole body of Saccharomyces cerevisiae: Architecture and assembly of the core components". Current Topics in Developmental Biology (Elsevier) 49: 105–132. http://www.sciencedirect.com./science/article/pii/S0070215399490064. Retrieved 04/29/2012.
^ Francis, Susan; Trisha Davis (1999). "The spindle pole body of Saccharomyces cerevisiae: Architecture and assembly of the core components". Current Topics in Developmental Biology (Elsevier) 49: 105–132. http://www.sciencedirect.com./science/article/pii/S0070215399490064. Retrieved 04/29/2012.
^ Sancho, David; Miguel Vicente-Manzanares, Maria Mittelbrunn, Maria Montoya, Monica Gordon-Alonso, Juan Serrador, Francisco Sanchez-Madrid (11). "Regulation of Microtubule Organizing Center Orientation and Actomyosin Cytoskeleton Rearrangement During Immune Interactions". Immunological Reviews (Wiley Online Library) 189 (1): 84–97. http://onlinelibrary.wiley.com/doi/10.1034/j.1600-065X.2002.18908.x/full.
^ Sancho, David; Miguel Vicente-Manzanares, Maria Mittelbrunn, Maria Montoya, Monica Gordon-Alonso, Juan Serrador, Francisco Sanchez-Madrid (11). "Regulation of Microtubule Organizing Center Orientation and Actomyosin Cytoskeleton Rearrangement During Immune Interactions". Immunological Reviews (Wiley Online Library) 189 (1): 84–97. http://onlinelibrary.wiley.com/doi/10.1034/j.1600-065X.2002.18908.x/full.
^ Sancho, David; Miguel Vicente-Manzanares, Maria Mittelbrunn, Maria Montoya, Monica Gordon-Alonso, Juan Serrador, Francisco Sanchez-Madrid (11). "Regulation of Microtubule Organizing Center Orientation and Actomyosin Cytoskeleton Rearrangement During Immune Interactions". Immunological Reviews (Wiley Online Library) 189 (1): 84–97. http://onlinelibrary.wiley.com/doi/10.1034/j.1600-065X.2002.18908.x/full.

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MeSH A11.284.195.190.750.585

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English Journal

Nezha/CAMSAP3 and CAMSAP2 cooperate in epithelial-specific organization of noncentrosomal microtubules.

Tanaka N, Meng W, Nagae S, Takeichi M.SourceRIKEN Center for Developmental Biology, Kobe 650-0047, Japan.
Proceedings of the National Academy of Sciences of the United States of America.Proc Natl Acad Sci U S A.2012 Nov 19. [Epub ahead of print]
Major microtubules in epithelial cells are not anchored to the centrosome, in contrast to the centrosomal radiation of microtubules in other cell types. It remains to be discovered how these epithelial microtubules are generated and stabilized at noncentrosomal sites. Here, we found that Nezha [also
PMID 23169647

Microtubule dynamics alter the interphase nucleus.

Gerlitz G, Reiner O, Bustin M.SourceProtein Section, Laboratory of Metabolism, National Cancer Institute, US National Institutes of Health, Bethesda, MD, 20892, USA, gabi.gerlitz@gmail.com.
Cellular and molecular life sciences : CMLS.Cell Mol Life Sci.2012 Nov 2. [Epub ahead of print]
Microtubules are known to drive chromosome movements and to induce nuclear envelope breakdown during mitosis and meiosis. Here we show that microtubules can enforce nuclear envelope folding and alter the levels of nuclear envelope-associated heterochromatin during interphase, when the nuclear envelo
PMID 23117601

Japanese Journal

Dynamic Change of Cellular Localization of Microtubule-Organizing Center During Conjugation of Ciliate Tetrahymena thermophila

Kushida Yasuharu,Takaine Masak,Nakano Kentaro [他]
Zoological science 32(1), 25-32, 2015-01
NAID 40020363740

Functional implications of the Golgi and microtubular network in gonadotropes.

渡部剛,暮地本宙己,Koga Daisuke,Hosaka Masahiro,牛木辰男
Molecular and Cellular Endocrinology 385(1-2), 88-96, 2014-03
… At the center of the spherical Golgi, a pair of centrioles is situated as a microtubule-organizing center from which radiating microtubules isotropically extend toward the cell periphery. …
NAID 120005496543

YB-1 Functions as a Porter To Lead Influenza Virus Ribonucleoprotein Complexes to Microtubules

Kawaguchi Atsushi,Matsumoto Ken,Nagata Kyosuke
Journal of virology 86(20), 11086-11095, 2012-10
… After nuclear export, using YB-1 knockdown cells and in vitro reconstituted systems, YB-1 was shown to be required for the interaction of vRNP exported from the nucleus with microtubules around the microtubule-organizing center (MTOC), where Rab11a-positive recycling endosomes were located. …
NAID 120005399279