scholarly journals A Combinatorial MAP Code Dictates Polarized Microtubule Transport

2019 ◽  
Author(s):  
Brigette Y. Monroy ◽  
Tracy C. Tan ◽  
Janah May Oclaman ◽  
Jisoo S. Han ◽  
Sergi Simo ◽  
...  
Keyword(s):  
Molecular Motors ◽  
Cytoplasmic Dynein ◽  
Directed Movement ◽  
Microtubule Associated Proteins ◽  
In Vitro Reconstitution ◽  
Microtubule Transport ◽  
Associated Proteins ◽  
Transient Interactions ◽  
Intracellular Sorting

ABSTRACTMany eukaryotic cells distribute their intracellular components through asymmetrically regulated active transport driven by molecular motors along microtubule tracks. While intrinsic and extrinsic regulation of motor activity exists, what governs the overall distribution of activated motor-cargo complexes within cells remains unclear. Here, we utilize in vitro reconstitution of purified motor proteins and non-enzymatic microtubule-associated proteins (MAPs) to demonstrate that these MAPs exhibit distinct influences on the motility of the three main classes of transport motors: kinesin-1, kinesin-3, and cytoplasmic dynein. Further, we dissect how combinations of MAPs affect motors, and reveal how transient interactions between MAPs and motors may promote these effects. From these data, we propose a general “MAP code” that has the capacity to strongly bias directed movement along microtubules and helps elucidate the intricate intracellular sorting observed in highly polarized cells such as neurons.

scholarly journals Functionally distinct isoforms of dynactin are expressed in human neurons.

1996 ◽  
Vol 7 (8) ◽  
pp. 1167-1180 ◽  
Author(s):  
M K Tokito ◽  
D S Howland ◽  
V M Lee ◽  
E L Holzbaur
Keyword(s):  
Cytoplasmic Dynein ◽  
Binding Motif ◽  
Binding Assays ◽  
Microtubule Binding ◽  
Microtubule Associated Proteins ◽  
Human Neurons ◽  
Alternative Mrna Splicing ◽  
Associated Proteins ◽  
Dynactin Complex

P150Glued is the largest subunit of dynactin, which binds to cytoplasmic dynein and activates vesicle transport along microtubules. We have isolated human cDNAs encoding p150Glued as well as a 135-kDa isoform; these isoforms are expressed in human brain by alternative mRNA splicing of the human DCTN1 gene. The p135 isoform lacks the consensus microtubule-binding motif shared by members of the p150Glued/Glued/CLIP-170/BIK1 family of microtubule-associated proteins and, therefore, is predicted not to bind directly to microtubules. We used transient transfection assays and in vitro microtubule-binding assays to demonstrate that the p150 isoform binds to microtubules, but the p135 isoform does not. However, both isoforms bind to cytoplasmic dynein, and both partition similarly into cytosolic and membrane cellular fractions. Sequential immunoprecipitations with an isoform-specific antibody for p150 followed by a pan-isoform antibody revealed that, in brain, these polypeptides assemble to form distinct complexes, each of which sediments at approximately 20 S. On the basis of these observations, we hypothesize that there is a conserved neuronal function for a distinct form of the dynactin complex that cannot bind directly to cellular microtubules.

scholarly journals Mapmodulin, Cytoplasmic Dynein, and Microtubules Enhance the Transport of Mannose 6-Phosphate Receptors from Endosomes to theTrans-Golgi Network

1999 ◽  
Vol 10 (7) ◽  
pp. 2191-2197 ◽  
Author(s):  
Christian Itin ◽  
Nirit Ulitzur ◽  
Bettina Mühlbauer ◽  
Suzanne R. Pfeffer
Keyword(s):  
Mammalian Cells ◽  
Chinese Hamster Ovary Cells ◽  
Cytoplasmic Dynein ◽  
Vesicle Transport ◽  
Microtubule Associated Proteins ◽  
Late Endosomes ◽  
Associated Proteins ◽  
Mannose 6 Phosphate ◽  
Golgi Network

Late endosomes and the Golgi complex maintain their cellular localizations by virtue of interactions with the microtubule-based cytoskeleton. We study the transport of mannose 6-phosphate receptors from late endosomes to the trans-Golgi network in vitro. We show here that this process is facilitated by microtubules and the microtubule-based motor cytoplasmic dynein; transport is inhibited by excess recombinant dynamitin or purified microtubule-associated proteins. Mapmodulin, a protein that interacts with the microtubule-associated proteins MAP2, MAP4, and tau, stimulates the microtubule- and dynein-dependent localization of Golgi complexes in semi-intact Chinese hamster ovary cells. The present study shows that mapmodulin also stimulates the initial rate with which mannose 6-phosphate receptors are transported from late endosomes to thetrans-Golgi network in vitro. These findings represent the first indication that mapmodulin can stimulate a vesicle transport process, and they support a model in which the microtubule-based cytoskeleton enhances the efficiency of vesicle transport between membrane-bound compartments in mammalian cells.

scholarly journals Regulation of cytoplasmic dynein function in vivo by the Drosophila Glued complex.

1995 ◽  
Vol 131 (2) ◽  
pp. 411-425 ◽  
Author(s):  
M McGrail ◽  
J Gepner ◽  
A Silvanovich ◽  
S Ludmann ◽  
M Serr ◽  
...  
Keyword(s):  
Temporal Distribution ◽  
Cytoplasmic Dynein ◽  
Chain Gene ◽  
Gene Products ◽  
Wild Type ◽  
Microtubule Associated Proteins ◽  
Dynein Motor ◽  
Associated Proteins

The Drosophila Glued gene product shares sequence homology with the p150 component of vertebrate dynactin. Dynactin is a multiprotein complex that stimulates cytoplasmic dynein-mediated vesicle motility in vitro. In this report, we present biochemical, cytological, and genetic evidence that demonstrates a functional similarity between the Drosophila Glued complex and vertebrate dynactin. We show that, similar to the vertebrate homologues in dynactin, the Glued polypeptides are components of a 20S complex. Our biochemical studies further reveal differential expression of the Glued polypeptides, all of which copurify as microtubule-associated proteins. In our analysis of the Glued polypeptides encoded by the dominant mutation, Glued, we identify a truncated polypeptide that fails to assemble into the wild-type 20S complex, but retains the ability to copurify with microtubules. The spatial and temporal distribution of the Glued complex during oogenesis is shown by immunocytochemistry methods to be identical to the pattern previously described for cytoplasmic dynein. Significantly, the pattern of Glued distribution in oogenesis is dependent on dynein function, as well as several other gene products known to be required for proper dynein localization. In genetic complementation studies, we find that certain mutations in the cytoplasmic dynein heavy chain gene Dhc64C act as dominant suppressors or enhancers of the rough eye phenotype of the dominant Glued mutation. Furthermore, we show that a mutation that was previously isolated as a suppressor of the Glued mutation is an allele of Dhc64C. Together with the observed dependency of Glued localization on dynein function, these genetic interactions demonstrate a functional association between the Drosophila dynein motor and Glued complexes.

scholarly journals Competition between microtubule-associated proteins directs motor transport

2017 ◽  
Author(s):  
Brigette Y. Monroy ◽  
Danielle L. Sawyer ◽  
Bryce E. Ackermann ◽  
Melissa M. Borden ◽  
Tracy C. Tan ◽  
...  
Keyword(s):  
Molecular Motor ◽  
Cytoplasmic Dynein ◽  
Inhibitory Effect ◽  
Microtubule Associated Proteins ◽  
Motor Transport ◽  
Branch Formation ◽  
Microtubule Motor ◽  
Associated Proteins

Within cells, numerous motor and non-motor microtubule-associated proteins (MAPs) simultaneously converge on the microtubule lattice. How the binding activities of non-motor MAPs are coordinated and how they contribute to the balance and distribution of microtubule motor transport is unknown. Here, we examine the relationship between MAP7 and tau due to their antagonistic effects on neuronal branch formation and kinesin motility in vivo1–8. We find that MAP7 and tau compete for binding to microtubules, and determine a mechanism by which MAP7 displaces tau from the lattice. In striking contrast to the inhibitory effect of tau, MAP7 promotes kinesin-based transport in vivo and strongly enhances kinesin-1 binding to the microtubule in vitro, providing evidence for direct enhancement of motor motility by a MAP. In contrast, both MAP7 and tau strongly inhibit kinesin-3 and have no effect on cytoplasmic dynein, demonstrating that MAPs exhibit differential control over distinct classes of motors. Overall, these results reveal a general principle for how MAP competition dictates access to the microtubule to determine the correct distribution and balance of molecular motor activity.

Analysis of the Mechanism of Microtubule Dynamic Instability Using a UV Microbeam to Sever Elongating Microtubules

1988 ◽  
Vol 46 ◽  
pp. 122-123
Author(s):  
R.A Walker ◽  
S. Inoue ◽  
E.D. Salmon
Keyword(s):  
Dynamic Instability ◽  
Microtubule Dynamic ◽  
Gtp Hydrolysis ◽  
Abrupt Transition ◽  
Microtubule Associated Proteins ◽  
Asymmetrical Structure ◽  
Associated Proteins

Microtubules polymerized in vitro from tubulin purified free of microtubule-associated proteins exhibit dynamic instability (1,2,3). Free microtubule ends exist in persistent phases of elongation or rapid shortening with infrequent, but, abrupt transitions between these phases. The abrupt transition from elongation to rapid shortening is termed catastrophe and the abrupt transition from rapid shortening to elongation is termed rescue. A microtubule is an asymmetrical structure. The plus end grows faster than the minus end. The frequency of catastrophe of the plus end is somewhat greater than the minus end, while the frequency of rescue of the plus end in much lower than for the minus end (4).The mechanism of catastrophe is controversial, but for both the plus and minus microtubule ends, catastrophe is thought to be dependent on GTP hydrolysis. Microtubule elongation occurs by the association of tubulin-GTP subunits to the growing end. Sometime after incorporation into an elongating microtubule end, the GTP is hydrolyzed to GDP, yielding a core of tubulin-GDP capped by tubulin-GTP (“GTP-cap”).

Molecular architecture and functions of the neuronal cytoskeleton

1990 ◽  
Vol 48 (3) ◽  
pp. 2-3
Author(s):  
Nobutaka Hirokawa
Keyword(s):  
Major Elements ◽  
Molecular Structures ◽  
Organelle Transport ◽  
Molecular Architecture ◽  
Neuronal Morphogenesis ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
And Function ◽  
Small Clusters

In this symposium I will present our studies about the molecular architecture and function of the cytomatrix of the nerve cells. The nerve cell is a highly polarized cell composed of highly branched dendrites, cell body, and a single long axon along the direction of the impulse propagation. Each part of the neuron takes characteristic shapes for which the cytoskeleton provides the framework. The neuronal cytoskeletons play important roles on neuronal morphogenesis, organelle transport and the synaptic transmission. In the axon neurofilaments (NF) form dense arrays, while microtubules (MT) are arranged as small clusters among the NFs. On the other hand, MTs are distributed uniformly, whereas NFs tend to run solitarily or form small fascicles in the dendrites Quick freeze deep etch electron microscopy revealed various kinds of strands among MTs, NFs and membranous organelles (MO). These structures form major elements of the cytomatrix in the neuron. To investigate molecular nature and function of these filaments first we studied molecular structures of microtubule associated proteins (MAP1A, MAP1B, MAP2, MAP2C and tau), and microtubules reconstituted from MAPs and tubulin in vitro. These MAPs were all fibrous molecules with different length and formed arm like projections from the microtubule surface.

Microtubule motors and other maps

1990 ◽  
Vol 48 (3) ◽  
pp. 1-1
Author(s):  
Richard B. Vallee
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Cytoplasmic Dynein ◽  
Organelle Transport ◽  
Structural Components ◽  
Microtubule Associated Proteins ◽  
Microtubule Motors ◽  
Associated Proteins ◽  
The Subject ◽  
Intracellular Motility

Microtubules are involved in a number of forms of intracellular motility, including mitosis and bidirectional organelle transport. Purified microtubules from brain and other sources contain tubulin and a diversity of microtubule associated proteins (MAPs). Some of the high molecular weight MAPs - MAP 1A, 1B, 2A, and 2B - are long, fibrous molecules that serve as structural components of the cytamatrix. Three MAPs have recently been identified that show microtubule activated ATPase activity and produce force in association with microtubules. These proteins - kinesin, cytoplasmic dynein, and dynamin - are referred to as cytoplasmic motors. The latter two will be the subject of this talk.Cytoplasmic dynein was first identified as one of the high molecular weight brain MAPs, MAP 1C. It was determined to be structurally equivalent to ciliary and flagellar dynein, and to produce force toward the minus ends of microtubules, opposite to kinesin.

scholarly journals Stu2p binds tubulin and undergoes an open-to-closed conformational change

2006 ◽  
Vol 172 (7) ◽  
pp. 1009-1022 ◽  
Author(s):  
Jawdat Al-Bassam ◽  
Mark van Breugel ◽  
Stephen C. Harrison ◽  
Anthony Hyman
Keyword(s):  
Conformational Change ◽  
Conformational Transition ◽  
Budding Yeast ◽  
Microtubule Dynamics ◽  
Open Structure ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
The Common

Stu2p from budding yeast belongs to the conserved Dis1/XMAP215 family of microtubule-associated proteins (MAPs). The common feature of proteins in this family is the presence of HEAT repeat–containing TOG domains near the NH2 terminus. We have investigated the functions of the two TOG domains of Stu2p in vivo and in vitro. Our data suggest that Stu2p regulates microtubule dynamics through two separate activities. First, Stu2p binds to a single free tubulin heterodimer through its first TOG domain. A large conformational transition in homodimeric Stu2p from an open structure to a closed one accompanies the capture of a single free tubulin heterodimer. Second, Stu2p has the capacity to associate directly with microtubule ends, at least in part, through its second TOG domain. These two properties lead to the stabilization of microtubules in vivo, perhaps by the loading of tubulin dimers at microtubule ends. We suggest that this mechanism of microtubule regulation is a conserved feature of the Dis1/XMAP215 family of MAPs.

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