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1
Inside the Brain: Unraveling the Mystery of Alzheimer
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::2010/07/29::
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2
Microtubules in Arabidopsis Root Hair --- TIRF microscopy
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::2011/08/31::
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3
Microtubule dynamics in the clasp-1 mutant
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Chemokine Signaling Regulates Tau Pathology
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::2011/03/30::
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Wierd dots in cells (best viewed in full-screen)
Wierd dots in cells (best viewed in full-screen)
::2011/03/30::
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7
Rotating nuclei - part1 (best viewed in full-screen)
Rotating nuclei - part1 (best viewed in full-screen)
::2011/03/30::
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8
VisiTech VT-Hawk Confocal Images of RGB Minispindles
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::2010/12/10::
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Kinesin-1-Mediated Transport of AMPARs Contributes to Synaptic Strength
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::2013/12/18::
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10
Three color live imaging cells
Three color live imaging cells
::2010/03/10::
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11
LLC PK1 mEm H2B mRuby EB3 60x Run 01 15 fps
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::2009/08/03::
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12
The Kinesin Linear Motor
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::2010/03/11::
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13
EB1 and Microtubules
EB1 and Microtubules
::2012/01/10::
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14
Microtubule
Microtubule 'Worms Crawling'
::2014/04/07::
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15
fantastic vesicle traffic
fantastic vesicle traffic
::2009/04/11::
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16
The Ciliopathy-associated Protein Homologs RPGRIP1
The Ciliopathy-associated Protein Homologs RPGRIP1
::2011/08/29::
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17
Microtubules in distress
Microtubules in distress
::2011/05/02::
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18
biosights: October 28, 2013 - A framework for understanding muscle microtubules
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::2013/10/28::
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19
TEDx Brussels 2010 - Stuart Hameroff - Do we have a quantum Soul?
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::2011/01/18::
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20
Protein Modification (Golgi)
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::2008/04/07::
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21
biosights: September 2, 2013 - Shrinking microtubules pull the centrosome into place
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::2013/09/03::
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22
Localization of telomeres and telomere-associated proteins in telomerase-negative Saccharomyces cer
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::2010/12/02::
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23
Cellulose microtubule
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::2012/10/12::
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24
Mitosis: Splitting Up is Complicated - Crash Course Biology #12
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::2012/04/16::
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25
EB1
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::2012/01/10::
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26
Clarifying the Tubulin bit/qubit - Defending the Penrose-Hameroff Orch OR Model (Quantum Biology)
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::2010/10/28::
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27
Kinesin Transport Protein
Kinesin Transport Protein
::2007/10/05::
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28
The Inner Life of the Cell
The Inner Life of the Cell
::2011/07/11::
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29
Joubert syndrome disease protein trapped in cilia
Joubert syndrome disease protein trapped in cilia
::2013/12/09::
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30
Protein Trafficking
Protein Trafficking
::2008/03/03::
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31
Cilia and Flagella
Cilia and Flagella
::2012/11/12::
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32
How Microtubules are arranged in sperm tails to generate motion.
How Microtubules are arranged in sperm tails to generate motion.
::2010/11/23::
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33
Actin filament assembly
Actin filament assembly
::2012/11/25::
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34
A microtubule-based, dynein-dependent force induces local cell protrusions: Implications for neurit
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::2010/12/02::
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35
Motor proteins
Motor proteins
::2012/10/28::
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36
Mitochondrial transport along microtubules
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::2011/01/12::
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37
Proteins of Cell Membrane
Proteins of Cell Membrane
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38
Mitotic catastrophe triggered in human cancer cells by the viral protein apoptin - movie A
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Sorting It All Out: Signal-mediated Protein Trafficking in the Endosomal-Lysosomal System
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::2010/11/15::
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40
The Plasma Membrane
The Plasma Membrane
::2010/02/09::
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41
Tubulin GFP
Tubulin GFP
::2012/01/10::
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42
A Neuron-Specific Protein found in Skeletal Muscle by Raffaele Pilla - Dissertation.com
A Neuron-Specific Protein found in Skeletal Muscle by Raffaele Pilla - Dissertation.com
::2012/05/14::
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43
ELASTIN AND FIBRILLIN - ASSOCIATED DISEASES
ELASTIN AND FIBRILLIN - ASSOCIATED DISEASES
::2012/05/11::
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44
4D Imaging of Protein Aggregation in Live Cells
4D Imaging of Protein Aggregation in Live Cells
::2014/02/27::
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45
EB1 Microtubule trajectories on Crossbow shaped micropattern
EB1 Microtubule trajectories on Crossbow shaped micropattern
::2011/01/14::
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46
Tubulin and Histone GFP
Tubulin and Histone GFP
::2012/01/10::
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47
Simply Science Episode 30: The Proteins Behind Alzheimer
Simply Science Episode 30: The Proteins Behind Alzheimer's
::2010/12/14::
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48
The Motor Protein Melody
The Motor Protein Melody
::2013/01/29::
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49
GDF11 Is a Circulating Factor that Reverses Age-Related Cardiac Hypertrophy
GDF11 Is a Circulating Factor that Reverses Age-Related Cardiac Hypertrophy
::2013/04/24::
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50
Motor Protein (moderate load)
Motor Protein (moderate load)
::2011/05/16::
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RESULTS [51 .. 101]
From Wikipedia, the free encyclopedia
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In cell biology, microtubule-associated proteins (MAPs) are proteins that interact with the microtubules of the cellular cytoskeleton.

Function[edit]

MAPs bind to the tubulin subunits that make up microtubules to regulate their stability. A large variety of MAPs have been identified in many different cell types, and they have been found to carry out a wide range of functions. These include both stabilizing and destabilizing microtubules, guiding microtubules towards specific cellular locations, cross-linking microtubules and mediating the interactions of microtubules with other proteins in the cell [1].

Within the cell, MAPs bind directly to the tubulin dimers of microtubules. This binding can occur with either polymerized or depolymerized tubulin, and in most cases leads to the stabilization of microtubule structure, further encouraging polymerization. Usually, it is the C-terminal domain of the MAP that interacts with tubulin, while the N-terminal domain can bind with cellular vesicles, intermediate filaments or other microtubules. MAP-microtubule binding is regulated through MAP phosphorylation. This is accomplished through the function of the microtubule-affinity-regulating-kinase (MARK) protein. Phosphorylation of the MAP by the MARK causes the MAP to detach from any bound microtubules [2]. This detachment is usually associated with a destabilization of the microtubule causing it to fall apart. In this way the stabilization of microtubules by MAPs is regulated within the cell through phosphorylation.

Types[edit]

The numerous identified MAPs have been largely divided into two categories: Type I including MAP1 proteins and type II including MAP2, MAP4 and tau proteins.

Type I: MAP1[edit]

MAP1a (MAP1A) and MAP1b (MAP1B), which make up the MAP1 family, bind to microtubules differently from other MAPs, utilizing charged interactions [3]. While the C-terminals of these MAPs bind the microtubules, the N-terminals bind other parts of the cytoskeleton or the plasma membrane to control spacing of the microtubule within the cell. Members of the MAP1 family are found in the axons and dendrites of nerve cells [4].

Type II: MAP2, MAP4 and tau[edit]

Also found exclusively in nerve cells are the most well studied MAPs—MAP2 and tau (MAPT)—which participate in determining the structure of different parts of nerve cells, with MAP2 being found mostly in dendrites and tau in the axon. These proteins have a conserved C-terminal microtubule-binding domain and variable N-terminal domains projecting outwards, probably interacting with other proteins. MAP2 and tau stabilize microtubules, and thus shift the reaction kinetics in favor of addition of new subunits, accelerating microtubule growth. Both MAP2 and tau have been shown to stabilize microtubules by binding to the outer surface of the microtubule protofilaments.[5][6] A single study has suggested that MAP2 and tau bind on the inner microtubule surface on the same site in tubulin monomers as the drug Taxol, which is used in treating cancer,[7] but this study has not been confirmed. MAP2 binds in a cooperative manner, with many MAP2 proteins binding a single microtubule to promote stabilization. Tau has the additional function of facilitating bundling of microtubules within the nerve cell.[8]

The function of tau has been linked to the neurological condition Alzheimer's disease. In the nervous tissue of Alzheimer's patients, tau forms abnormal aggregates. This aggregated tau is often severely modified, most commonly through hyperphosphorylation. As described above, phosphorylation of MAPs causes them to detach from microtubules. Thus, the hyperphosphorylation of tau leads to massive detachment, which in turn greatly reduces the stability of microtubules in nerve cells.[9] This increase in microtubule instability may be one of the main causes of the symptoms of Alzheimer's disease.

In contrast to the MAPs described above, MAP4 (MAP4) is not confined to just nerve cells, but rather can be found in nearly all types of cells. Like MAP2 and tau, MAP4 is responsible for stabilization of microtubules.[10] MAP4 has also been linked to the process of cell division.[11]

Other MAPs, and naming issues[edit]

Besides the classic MAP groups, novel MAPs have been identified that bind the length of the microtubules. These include STOP (also known as MAP6), and ensconsin (also known as MAP7).

In addition, plus end tracking proteins, which bind to the very tip of growing microtubules, have also been identified. These include EB1, EB2, EB3, p150Glued, Dynamitin, Lis1, CLIP170, CLIP115, CLASP1, and CLASP2.

Another MAP whose function has been investigated during cell division is known as XMAP215 (the "X" stands for Xenopus). XMAP215 has generally been linked to microtubule stabilization. During mitosis the dynamic instability of microtubules has been observed to rise approximately tenfold. This is partly due to phosphorylation of XMAP215, which makes catastrophes (rapid depolymerization of microtubules) more likely [12]. In this way the phosphorylation of MAPs plays a role in mitosis.

There are many other proteins which affect microtubule behavior, such as catastrophin, which destabilizes microtubules, katanin, which severs them, and a number of motor proteins that transport vesicles along them. Certain motor proteins were originally designated as MAPs before it was found that they utilized ATP hydrolysis to transport cargo. In general, all these proteins are not considered "MAPs" because they do not bind directly to tubulin monomers, a defining characteristic of MAPs [13]. MAPs bind directly to microtubules to stabilize or destabilize them and link them to various cellular components including other microtubules.

See also[edit]

References[edit]

External links[edit]

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