scholarly journals A molecular mechanism for salt stress-induced microtubule array formation in Arabidopsis

2018 ◽  
Author(s):  
Christopher Kesten ◽  
Arndt Wallmann ◽  
René Schneider ◽  
Heather E. McFarlane ◽  
Anne Diehl ◽  
...  
Keyword(s):  
Salt Stress ◽  
Molecular Mechanism ◽  
Plant Cells ◽  
Binding Motif ◽  
Related Protein ◽  
Microtubule Associated Proteins ◽  
Protein Tau ◽  
Intrinsically Disordered ◽  
Associated Proteins ◽  
Hydrophobic Binding

AbstractMicrotubules are filamentous structures necessary for cell division, motility and morphology, with dynamics critically regulated by microtubule-associated proteins (MAPs). We outline the molecular mechanism by which the MAP, COMPANION OF CELLULOSE SYNTHASE1 (CC1), controls microtubule bundling and dynamics to sustain plant growth under salt stress. CC1 contains an intrinsically disordered N-terminus that links microtubules at evenly distributed distances through four conserved hydrophobic regions. NMR analyses revealed that two neighboring residues in the first hydrophobic binding motif are crucial for the microtubule interaction, which we confirmed through live cell analyses. The microtubule-binding mechanism of CC1 is remarkably similar to that of the prominent neuropathology-related protein Tau, indicating evolutionary convergence of MAP functions across animal and plant cells.

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 A novel microtubule-binding motif identified in a high molecular weight microtubule-associated protein from Trypanosoma brucei

1992 ◽  
Vol 117 (1) ◽  
pp. 95-103 ◽  
Author(s):  
A Hemphill ◽  
M Affolter ◽  
T Seebeck
Keyword(s):  
Molecular Weight ◽  
Amino Acid ◽  
Trypanosoma Brucei ◽  
Binding Motif ◽  
Amino Acid Repeat ◽  
Microtubule Binding ◽  
Microtubule Associated Proteins ◽  
Repeat Units ◽  
Associated Proteins

The major component of the cytoskeleton of the parasitic hemoflagellate Trypanosoma brucei is a membrane skeleton which consists of a single layer of tightly spaced microtubules. This array encloses the entire cell body, and it is apposed to, and connected with, the overlying cell membrane. The microtubules of this array contain numerous microtubule-associated proteins. Prominent among those is a family of high molecular weight, repetitive proteins which consist to a large extent of tandemly arranged 38-amino acid repeat units. The binding of one of these proteins, MARP-1, to microtubules has now been characterized in vitro and in vivo. MARP-1 binds to microtubules via tubulin domains other than the COOH-termini used by microtubule-associated proteins from mammalian brain, e.g., MAP2 or Tau. In vitro binding assays using recombinant protein, as well as transfection of mammalian cell lines, have established that the repetitive 38-amino acid repeat units represent a novel microtubule-binding motif. This motif is very similar in length to those of the mammalian microtubule-associated proteins Tau, MAP2, and MAP-U, but both its sequence and charge are different. The observation that the microtubule-binding motifs both of the neural and the trypanosomal proteins are of similar length may reflect the fact that both mediate binding to the same repetitive surface, the microtubule, while their sequence and charge differences are in agreement with the observation that they interact with different domains of the tubulins.

WIPI2b and Atg16L1: setting the stage for autophagosome formation

2014 ◽  
Vol 42 (5) ◽  
pp. 1327-1334 ◽  
Author(s):  
Michael I. Wilson ◽  
Hannah C. Dooley ◽  
Sharon A. Tooze
Keyword(s):  
Endoplasmic Reticulum ◽  
Regulatory Network ◽  
Recent Progress ◽  
Direct Interaction ◽  
Related Protein ◽  
Autophagosome Formation ◽  
Microtubule Associated Proteins ◽  
Cellular Energy ◽  
Associated Proteins ◽  
Cellular Components

The double-membraned autophagosome organelle is an integral part of autophagy, a process that recycles cellular components by non-selectively engulfing and delivering them to lysosomes where they are digested. Release of metabolites from this process is involved in cellular energy homoeostasis under basal conditions and during nutrient starvation. Selective engulfment of protein aggregates and dysfunctional organelles by autophagosomes also prevents disruption of cellular metabolism. Autophagosome formation in animals is crucially dependent on the unique conjugation of a group of ubiquitin-like proteins in the microtubule-associated proteins 1A/1B light chain 3 (LC3) family to the headgroup of phosphatidylethanolamine (PE) lipids. LC3 lipidation requires a cascade of ubiquitin-like ligase and conjugation enzymes. The present review describes recent progress and discovery of the direct interaction between the PtdIns3P effector WIPI2b and autophagy-related protein 16-like 1 (Atg16L1), a component of the LC3-conjugation complex. This interaction makes the link between endoplasmic reticulum (ER)-localized production of PtdIns3P, triggered by the autophagy regulatory network, and recruitment of the LC3-conjugation complex crucial for autophagosome formation.

scholarly journals The Reduced Longitudinal Growth Induced by Overexpression of pPLAIIIγ Is Regulated by Genes Encoding Microtubule-Associated Proteins

Plants ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 2615
Author(s):  
Jin Hoon Jang ◽  
Hae Seong Seo ◽  
Ok Ran Lee
Keyword(s):  
Cell Expansion ◽  
Plant Cells ◽  
Ethylene Biosynthesis ◽  
Growth Patterns ◽  
Microtubule Associated Proteins ◽  
Radial Cell ◽  
Genes Encoding ◽  
Associated Proteins ◽  
Transcriptional Modulation ◽  
Radial Cell Expansion

There are three subfamilies of patatin-related phospholipase A (pPLA) group of genes: pPLAI, pPLAII, and pPLAIII. Among the four members of pPLAIIIs (α, β, γ, δ), the overexpression of three isoforms (α, β, and δ) displayed distinct morphological growth patterns, in which the anisotropic cell expansion was disrupted. Here, the least studied pPLAIIIγ was characterized, and it was found that the overexpression of pPLAIIIγ in Arabidopsis resulted in longitudinally reduced cell expansion patterns, which are consistent with the general phenotype induced by pPLAIIIs overexpression. The microtubule-associated protein MAP18 was found to be enriched in a pPLAIIIδ overexpressing line in a previous study. This indicates that factors, such as microtubules and ethylene biosynthesis, are involved in determining the radial cell expansion patterns. Microtubules have long been recognized to possess functional key roles in the processes of plant cells, including cell division, growth, and development, whereas ethylene treatment was reported to induce the reorientation of microtubules. Thus, the possible links between the altered anisotropic cell expansion and microtubules were studied. Our analysis revealed changes in the transcriptional levels of microtubule-associated genes, as well as phospholipase D (PLD) genes, upon the overexpression of pPLAIIIγ. Overall, our results suggest that the longitudinally reduced cell expansion observed in pPLAIIIγ overexpression is driven by microtubules via transcriptional modulation of the PLD and MAP genes. The altered transcripts of the genes involved in ethylene-biosynthesis in pPLAIIIγOE further support the conclusion that the typical phenotype is derived from the link with microtubules.

scholarly journals Structure and Functions of Microtubule Associated Proteins Tau and MAP2c: Similarities and Differences

Biomolecules ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 105 ◽  
Author(s):  
Kateřina Melková ◽  
Vojtěch Zapletal ◽  
Subhash Narasimhan ◽  
Séverine Jansen ◽  
Jozef Hritz ◽  
...  
Keyword(s):  
Function Analysis ◽  
Biological Activities ◽  
Structural Features ◽  
Sequence Motifs ◽  
Filamentous Actin ◽  
Structural Motifs ◽  
Microtubule Associated Proteins ◽  
Intrinsically Disordered ◽  
Associated Proteins ◽  
The Stability

The stability and dynamics of cytoskeleton in brain nerve cells are regulated by microtubule associated proteins (MAPs), tau and MAP2. Both proteins are intrinsically disordered and involved in multiple molecular interactions important for normal physiology and pathology of chronic neurodegenerative diseases. Nuclear magnetic resonance and cryo-electron microscopy recently revealed propensities of MAPs to form transient local structures and long-range contacts in the free state, and conformations adopted in complexes with microtubules and filamentous actin, as well as in pathological aggregates. In this paper, we compare the longest, 441-residue brain isoform of tau (tau40), and a 467-residue isoform of MAP2, known as MAP2c. For both molecules, we present transient structural motifs revealed by conformational analysis of experimental data obtained for free soluble forms of the proteins. We show that many of the short sequence motifs that exhibit transient structural features are linked to functional properties, manifested by specific interactions. The transient structural motifs can be therefore classified as molecular recognition elements of tau40 and MAP2c. Their interactions are further regulated by post-translational modifications, in particular phosphorylation. The structure-function analysis also explains differences between biological activities of tau40 and MAP2c.

Looking for novel functions of tau

2012 ◽  
Vol 40 (4) ◽  
pp. 653-655 ◽  
Author(s):  
Jesus Avila ◽  
Elena Gomez de Barreda ◽  
Almudena Fuster-Matanzo ◽  
Diana Simón ◽  
María Llorens-Martín ◽  
...  
Keyword(s):  
Cell Death ◽  
Neurodegenerative Disorders ◽  
Extracellular Space ◽  
Neuronal Cell Death ◽  
Neuronal Cell ◽  
Tau Pathology ◽  
Microtubule Associated Proteins ◽  
Protein Tau ◽  
Adult Mice ◽  
Associated Proteins

The lack or excess of the protein tau can be deleterious for neurons. The absence of tau can result in retarded neurogenesis and neuronal differentiation, although adult mice deficient in tau are viable, probably because of the compensation of the loss of tau by other MAPs (microtubule-associated proteins). On the contrary, the overexpression of tau can be toxic for the cell. One way to reduce intracellular tau levels can be achieved by its secretion through microvesicles to the extracellular space. Furthermore, tau can be found in the extracellular space because of the neuronal cell death occurring in neurodegenerative disorders such as Alzheimer's disease. The presence of toxic extracellular tau could be the mechanism for the spreading of tau pathology in these neurodegenerative disorders.

scholarly journals Tau stabilizes microtubules by binding at the interface between tubulin heterodimers

2015 ◽  
Vol 112 (24) ◽  
pp. 7501-7506 ◽  
Author(s):  
Harindranath Kadavath ◽  
Romina V. Hofele ◽  
Jacek Biernat ◽  
Satish Kumar ◽  
Katharina Tepper ◽  
...  
Keyword(s):  
Small Groups ◽  
Cell Morphology ◽  
Binding Sites ◽  
Spatial Organization ◽  
Dynamic Nature ◽  
Conserved Residues ◽  
Microtubule Associated Proteins ◽  
Protein Tau ◽  
Microtubule Polymerization ◽  
Associated Proteins

The structure, dynamic behavior, and spatial organization of microtubules are regulated by microtubule-associated proteins. An important microtubule-associated protein is the protein Tau, because its microtubule interaction is impaired in the course of Alzheimer’s disease and several other neurodegenerative diseases. Here, we show that Tau binds to microtubules by using small groups of evolutionary conserved residues. The binding sites are formed by residues that are essential for the pathological aggregation of Tau, suggesting competition between physiological interaction and pathogenic misfolding. Tau residues in between the microtubule-binding sites remain flexible when Tau is bound to microtubules in agreement with a highly dynamic nature of the Tau–microtubule interaction. By binding at the interface between tubulin heterodimers, Tau uses a conserved mechanism of microtubule polymerization and, thus, regulation of axonal stability and cell morphology.

Characterization of microtubules by dark-field STEM and replication

1991 ◽  
Vol 49 ◽  
pp. 152-153
Author(s):  
S.B. Andrews ◽  
R.D. Leapman ◽  
P.E. Gallant ◽  
T.S. Reese
Keyword(s):  
Protein Interactions ◽  
Low Dose ◽  
Unit Length ◽  
Dark Field ◽  
Carbon Films ◽  
Microtubule Associated Proteins ◽  
Molecular Weights ◽  
Freeze Dried ◽  
Protein Motors ◽  
Associated Proteins

As part of a study on protein interactions involved in microtubule (MT)-based transport, we used the VG HB501 field-emission STEM to obtain low-dose dark-field mass maps of isolated, taxol-stabilized MTs and correlated these micrographs with detailed stereo images from replicas of the same MTs. This approach promises to be useful for determining how protein motors interact with MTs. MTs prepared from bovine and squid brain tubulin were purified and free from microtubule-associated proteins (MAPs). These MTs (0.1-1 mg/ml tubulin) were adsorbed to 3-nm evaporated carbon films supported over Formvar nets on 600-m copper grids. Following adsorption, the grids were washed twice in buffer and then in either distilled water or in isotonic or hypotonic ammonium acetate, blotted, and plunge-frozen in ethane/propane cryogen (ca. -185 C). After cryotransfer into the STEM, specimens were freeze-dried and recooled to ca.-160 C for low-dose (<3000 e/nm2) dark-field mapping. The molecular weights per unit length of MT were determined relative to tobacco mosaic virus standards from elastic scattering intensities. Parallel grids were freeze-dried and rotary shadowed with Pt/C at 14°.

Filaments and membranes in the mitotic apparatus

1983 ◽  
Vol 41 ◽  
pp. 544-547
Author(s):  
Kent McDonald
Keyword(s):  
Intermediate Filaments ◽  
Mitotic Spindle ◽  
Mitotic Apparatus ◽  
Light Microscope Level ◽  
Microtubule Associated Proteins ◽  
Recent Developments ◽  
Associated Proteins ◽  
Force Generator ◽  
Spindle Function ◽  
Antibody Technology

At the light microscope level the recent developments and interest in antibody technology have permitted the localization of certain non-microtubule proteins within the mitotic spindle, e.g., calmodulin, actin, intermediate filaments, protein kinases and various microtubule associated proteins. Also, the use of fluorescent probes like chlorotetracycline suggest the presence of membranes in the spindle. Localization of non-microtubule structures in the spindle at the EM level has been less rewarding. Some mitosis researchers, e.g., Rarer, have maintained that actin is involved in mitosis movements though the bulk of evidence argues against this interpretation. Others suggest that a microtrabecular network such as found in chromatophore granule movement might be a possible force generator but there is little evidence for or against this view. At the level of regulation of spindle function, Harris and more recently Hepler have argued for the importance of studying spindle membranes. Hepler also believes that membranes might play a structural or mechanical role in moving chromosomes.

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