scholarly journals Overexpression of tau in a nonneuronal cell induces long cellular processes.

1991 ◽  
Vol 114 (4) ◽  
pp. 725-733 ◽  
Author(s):  
J Knops ◽  
K S Kosik ◽  
G Lee ◽  
J D Pardee ◽  
L Cohen-Gould ◽  
...  
Keyword(s):  
Cell Shape ◽  
Single Gene ◽  
Sf9 Cells ◽  
Cdna Insert ◽  
Microscopic Appearance ◽  
Microtubule Associated Proteins ◽  
Microtubule Stabilization ◽  
Cellular Processes ◽  
Associated Proteins ◽  
Axonal Compartment

The ways in which the various microtubule-associated proteins (MAPs) contribute to cellular function are unknown beyond the ability of these proteins to modify microtubule dynamics. One member of the MAP family, tau protein, is restricted in its distribution to the axonal compartment of neurons, and has therefore prompted studies that attempt to relate tau function to the generation or maintenance of this structure. Sf9 cells from a moth ovary, when infected with a baculovirus containing a tau cDNA insert, elaborate very long processes. This single gene product expressed in a foreign host cell grossly alters the normal rounded morphology of these cells. The slender, relatively nonbranched appearance of these processes as well as their uniform caliber resembles the light-microscopic appearance of axons observed in several neuronal culture systems. Immunolabeling of the tau-expressing Sf9 cells demonstrated tau reactivity in the induced processes, and EM that microtubule bundles were present in the processes. Microtubule stabilization alone was insufficient to generate processes, since taxol treatment did not alter the overall cell shape, despite the induction of microtubule bundling within the cell body.

scholarly journals Septins: New Microtubule Interacting Partners

2008 ◽  
Vol 8 ◽  
pp. 611-620 ◽  
Author(s):  
Rosalind Silverman-Gavrila ◽  
Lorelei Silverman-Gavrila
Keyword(s):  
Neurodegenerative Diseases ◽  
Cell Shape ◽  
Therapeutic Strategies ◽  
Microtubule Dynamics ◽  
Microtubule Cytoskeleton ◽  
Microtubule Associated Proteins ◽  
Cellular Processes ◽  
Microtubule Stability ◽  
Associated Proteins ◽  
Dependent Processes

Originally characterized as regulators of cytokinesis, septins were later implicated in other cellular processes. Recent studies show that septins have a broader role in microtubule-dependent processes, such as karyokinesis, exocytosis, and maintenance of cell shape. Many members of the septin family have been shown to colocalize or interact with the microtubule cytoskeleton, suggesting that these might be general properties of septins. Septins could play an important role in regulating microtubule dynamics by interacting with microtubule-associated proteins (MAPs) that modulate microtubule stability. Being able to associate with both microtubules and actin, septins can play an important role as adaptors between the two cytoskeletons and as regulators of processes in which both actin and microtubules are involved. As septins are associated with various neurodegenerative diseases and cancer, a better understanding of the biology of septins and their interactions with microtubules is important in order to develop possible therapeutic strategies for these diseases.

scholarly journals Intracellular Proadrenomedullin-Derived Peptides Decorate the Microtubules and Contribute to Cytoskeleton Function

Endocrinology ◽  
2008 ◽  
Vol 149 (6) ◽  
pp. 2888-2898 ◽  
Author(s):  
Dan L. Sackett ◽  
Laurent Ozbun ◽  
Enrique Zudaire ◽  
Lisa Wessner ◽  
John M. Chirgwin ◽  
...  
Keyword(s):  
Posttranslational Modifications ◽  
Morphological Changes ◽  
Microtubule Associated Proteins ◽  
Microtubule Stabilization ◽  
Gene Coding ◽  
Intracellular Compartments ◽  
Associated Proteins ◽  
G2 Phase ◽  
Interfering Rna

Adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP) are secretory hormones, but it is not unusual to find them in intracellular compartments. Using yeast-2 hybrid technology, we found interactions between AM and several microtubule-associated proteins (MAPs), and between PAMP and tubulin. Expression of fluorescent-tagged AM and PAMP as well as immunofluorescence for the native peptides showed a complete decoration of the microtubules and colocalization with other MAPs. PAMP, but not AM, bound to tubulin in vitro and destabilized tubulin polymerization. Down-regulation of the gene coding for both AM and PAMP through small interfering RNA technology resulted in morphological changes, microtubule stabilization, increase in posttranslational modifications of tubulin such as acetylation and detyrosination, reduction in cell motility, and partial arrest at the G2 phase of the cell cycle, when compared with cells transfected with the same vector carrying a scrambled sequence. These results show that PAMP is a novel MAP, whereas AM may be exerting more subtle effects in regulating cytoskeleton function.

scholarly journals Polarity orientation and assembly process of microtubule bundles in nocodazole-treated, MAP2c-transfected COS cells.

1995 ◽  
Vol 6 (8) ◽  
pp. 981-996 ◽  
Author(s):  
R Takemura ◽  
S Okabe ◽  
T Umeyama ◽  
N Hirokawa
Keyword(s):  
Electron Microscope ◽  
Model System ◽  
Sf9 Cells ◽  
Assembly Process ◽  
Microtubule Associated Proteins ◽  
Cos Cells ◽  
Microtubule Polarity ◽  
Neuronal Processes ◽  
Associated Proteins ◽  
Peripheral Cytoplasm

Microtubule bundles reminiscent of those found in neuronal processes are formed in fibroblasts and Sf9 cells that are transfected with the microtubule-associated proteins tau, MAP2, or MAP2c. To analyze the assembly process of these bundles and its relation to the microtubule polarity, we depolymerized the bundles formed in MAP2c-transfected COS cells using nocodazole, and observed the process of assembly of microtubule bundles after removal of the drug in cells microinjected with rhodamine-labeled tubulin. Within minutes of its removal, numerous short microtubule fragments were observed throughout the cytoplasm. These short fragments were randomly oriented and were already bundled. Somewhat longer, but still short bundles, were then found in the peripheral cytoplasm. These bundles became the primordium of the larger bundles, and gradually grew in length and width. The polarity orientation of microtubules in the reformed bundle as determined by "hook" procedure using electron microscope was uniform with the plus end distal to the cell nucleus. The results suggest that some mechanism(s) exists to orient the polarity of microtubules, which are not in direct continuity with the centrosome, during the formation of large bundles. The observed process presents a useful model system for studying the organization of microtubules that are not directly associated with the centrosomes, such as those observed in axons.

scholarly journals Stabilization and bundling of subtilisin-treated microtubules induced by microtubule associated proteins

1995 ◽  
Vol 108 (1) ◽  
pp. 357-367 ◽  
Author(s):  
Y. Saoudi ◽  
I. Paintrand ◽  
L. Multigner ◽  
D. Job
Keyword(s):  
Tau Proteins ◽  
Beta Tubulin ◽  
Alpha Tubulin ◽  
Microtubule Associated Proteins ◽  
Microtubule Stabilization ◽  
Microtubule Stability ◽  
Associated Proteins ◽  
Carboxy Terminal ◽  
Normal Sensitivity ◽  
Marked Resistance

The acidic carboxy-terminal regions of alpha- and beta-tubulin subunits are currently thought to be centrally involved in microtubule stability and in microtubule association with a variety of proteins (MAPs) such as MAP2 and tau proteins. Here, pure tubulin microtubules were exposed to subtilisin to produce polymers composed of cleaved tubulin subunits lacking carboxy termini. Polymer exposure to subtilisin was achieved in buffer conditions compatible with further tests of microtubule stability. Microtubules composed of normal alpha-tubulin and cleaved beta-tubulin were indistinguishable from control microtubules with regard to resistance to dilution-induced disassembly, to cold temperature-induced disassembly and to Ca(2+)-induced disassembly. Microtubules composed of cleaved alpha- and beta-tubulins showed normal sensitivity to dilution-induced disassembly and to low temperature-induced disassembly, but marked resistance to Ca(2+)-induced disassembly. Polymers composed of normal alpha-tubulin and cleaved beta-tubulin or of cleaved alpha- and beta-tubulins were stabilized in the presence of added MAP2, myelin basic protein and histone H1. Cleavage of tubulin carboxy termini greatly potentiated microtubule stabilization by tau proteins. We show that this potentiation of polymer stabilization can be ascribed to tau-induced microtubule bundling. In our working conditions, such bundling upon association with tau proteins occurred only in the case of microtubules composed of cleaved alpha- and beta-tubulins and triggered apparent microtubule cross-stabilization among the bundled polymers. These results, as well as immunofluorescence analysis, which directly showed interactions between subtilisin-treated microtubules and MAPs, suggest that the carboxy termini of alpha- and beta-tubulins are not primarily involved in the binding of MAPs onto microtubules. However, interactions between tubulin carboxy termini and MAPs remain possible and might be involved in the regulation of MAP-induced microtubule bundling.

scholarly journals The yeast homologue of the microtubule-associated protein Lis1 interacts with the sumoylation machinery and a SUMO-targeted ubiquitin ligase

2012 ◽  
Vol 23 (23) ◽  
pp. 4552-4566 ◽  
Author(s):  
Annabel Alonso ◽  
Sonia D'Silva ◽  
Maliha Rahman ◽  
Pam B. Meluh ◽  
Jacob Keeling ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Ubiquitin Ligases ◽  
Microtubule Associated Proteins ◽  
Sumo Protease ◽  
Cellular Processes ◽  
Associated Proteins ◽  
Novel Model ◽  
Intracellular Motility

Microtubules and microtubule-associated proteins are fundamental for multiple cellular processes, including mitosis and intracellular motility, but the factors that control microtubule-associated proteins (MAPs) are poorly understood. Here we show that two MAPs—the CLIP-170 homologue Bik1p and the Lis1 homologue Pac1p—interact with several proteins in the sumoylation pathway. Bik1p and Pac1p interact with Smt3p, the yeast SUMO; Ubc9p, an E2; and Nfi1p, an E3. Bik1p interacts directly with SUMO in vitro, and overexpression of Smt3p and Bik1p results in its in vivo sumoylation. Modified Pac1p is observed when the SUMO protease Ulp1p is inactivated. Both ubiquitin and Smt3p copurify with Pac1p. In contrast to ubiquitination, sumoylation does not directly tag the substrate for degradation. However, SUMO-targeted ubiquitin ligases (STUbLs) can recognize a sumoylated substrate and promote its degradation via ubiquitination and the proteasome. Both Pac1p and Bik1p interact with the STUbL Nis1p-Ris1p and the protease Wss1p. Strains deleted for RIS1 or WSS1 accumulate Pac1p conjugates. This suggests a novel model in which the abundance of these MAPs may be regulated via STUbLs. Pac1p modification is also altered by Kar9p and the dynein regulator She1p. This work has implications for the regulation of dynein's interaction with various cargoes, including its off-loading to the cortex.

Synthesis of putative microtubule-associated proteins by mouse blastocysts during early outgrowth in vitro

1984 ◽  
Vol 62 (9) ◽  
pp. 885-893 ◽  
Author(s):  
William R. Bates ◽  
Gerald M. Kidder
Keyword(s):  
Cell Shape ◽  
Polyacrylamide Gel Electrophoresis ◽  
Blastocyst Stage ◽  
Cytoskeletal Proteins ◽  
Biochemical Basis ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
Two Stages

The outgrowth of mouse trophoblast in culture provides a simplified model system analogous in certain ways to blastocyst implantation in vivo. Day-four blastocysts cultured for 3 days in vitro undergo extensive changes in cell shape and motility which are likely to involve the complex cytoskeletal system of the trophoblast cells. To explore the biochemical basis of these changes, one set of cytoskeletal proteins, the microtubule-associated proteins (MAPs), was studied. Day 4 blastocysts were labeled with [35S]methionine and blastocyst outgrowths, after 3 days in culture from the blastocyst stage, were labeled with [3H] methionine. Labeled embryos were disrupted and the soluble supernatants were pooled, and newly synthesized proteins from the two stages were coassembled with taxol-stabilized brain microtubule polymer enriched for MAP-binding sites. Double-labeled coassembly proteins (putative MAPS) were then released from the microtubule polymer by treatment with 0.35 M NaCl and analyzed by one-dimensional polyacrylamide gel electrophoresis. 3H/35S dpm ratios were determined for individual protein bands to compare the relative synthesis rates for day 4 blastocyst and day 3 outgrowth MAPs. In spite of the extensive changes in cell shape and motility associated with blastocyst outgrowth, a common set of putative MAPs characterizes the two stages investigated, including several in the size range of tau factors. No synthesis of high molecular weight MAPs comparable with MAP 1 or MAP 2 from brain was detected. The synthesis rates of individual MAPs relative to each other remain constant over this period and are likely coordinated with total protein and tubulin synthesis.

scholarly journals Human CLASP2 specifically regulates microtubule catastrophe and rescue

2018 ◽  
Vol 29 (10) ◽  
pp. 1168-1177 ◽  
Author(s):  
Elizabeth J. Lawrence ◽  
Göker Arpag˘ ◽  
Stephen R. Norris ◽  
Marija Zanic
Keyword(s):  
Growth Rates ◽  
Molecular Mechanisms ◽  
Direct Interaction ◽  
Microtubule Dynamics ◽  
Microtubule Associated Proteins ◽  
Cellular Processes ◽  
Associated Proteins ◽  
Microtubule Growth ◽  
Protein Components

Cytoplasmic linker-associated proteins (CLASPs) are microtubule-associated proteins essential for microtubule regulation in many cellular processes. However, the molecular mechanisms underlying CLASP activity are not understood. Here, we use purified protein components and total internal reflection fluorescence microscopy to investigate the effects of human CLASP2 on microtubule dynamics in vitro. We demonstrate that CLASP2 suppresses microtubule catastrophe and promotes rescue without affecting the rates of microtubule growth or shrinkage. Strikingly, when CLASP2 is combined with EB1, a known binding partner, the effects on microtubule dynamics are strongly enhanced. We show that synergy between CLASP2 and EB1 is dependent on a direct interaction, since a truncated EB1 protein that lacks the CLASP2-binding domain does not enhance CLASP2 activity. Further, we find that EB1 targets CLASP2 to microtubules and increases the dwell time of CLASP2 at microtubule tips. Although the temporally averaged microtubule growth rates are unaffected by CLASP2, we find that microtubules grown with CLASP2 display greater variability in growth rates. Our results provide insight into the regulation of microtubule dynamics by CLASP proteins and highlight the importance of the functional interplay between regulatory proteins at dynamic microtubule ends.

scholarly journals Distinct α- and β-tubulin isotypes are required for the positioning, differentiation and survival of neurons: new support for the ‘multi-tubulin’ hypothesis

2010 ◽  
Vol 30 (5) ◽  
pp. 319-330 ◽  
Author(s):  
Max A. Tischfield ◽  
Elizabeth C. Engle
Keyword(s):  
Nervous System ◽  
System Development ◽  
Nervous System Development ◽  
Cellular Functions ◽  
Microtubule Associated Proteins ◽  
Tubulin Isotypes ◽  
Cellular Processes ◽  
Associated Proteins ◽  
The Many ◽  
Β Tubulin

The many functions of the microtubule cytoskeleton are essential for shaping the development and maintaining the operation of the nervous system. With the recent discovery of congenital neurological disorders that result from mutations in genes that encode different α- and β-tubulin isotypes (TUBA1A, TUBB2B, TUBA8 and TUBB3), scientists have a novel paradigm to assess how select perturbations in microtubule function affect a range of cellular processes in humans. Moreover, important phenotypic distinctions found among the syndromes suggest that different tubulin isotypes can be utilized for distinct cellular functions during nervous system development. In the present review, we discuss: (i) the spectrum of congenital nervous system diseases that result from mutations in tubulin and MAPs (microtubule-associated proteins); (ii) the known or putative roles of these proteins during nervous system development; (iii) how the findings collectively support the ‘multi-tubulin’ hypothesis, which postulates that different tubulin isotypes may be required for specialized microtubule functions.

Dis1/TOG universal microtubule adaptors - one MAP for all?

2001 ◽  
Vol 114 (21) ◽  
pp. 3805-3812 ◽  
Author(s):  
Hiroyuki Ohkura ◽  
Miguel A. Garcia ◽  
Takashi Toda
Keyword(s):  
Molecular Mechanisms ◽  
Binding Activity ◽  
Mitotic Spindles ◽  
Microtubule Associated Proteins ◽  
Cellular Processes ◽  
Microtubule Motors ◽  
Associated Proteins ◽  
On Line ◽  
And Function ◽  
Centrosomal Proteins

Microtubules play central roles in various cellular processes in eukaryotes. The dynamics and organisation of interphase microtubules and mitotic spindles are dramatically altered during the cell cycle and development. However, the molecular mechanisms underlying this dynamic behaviour remain to be understood. In recent years, a novel family of microtubule-associated proteins (MAPs), the Dis1/TOG family, has emerged as a versatile regulator of microtubule function. These MAPs are highly conserved in eukaryotes from yeasts and plants to humans. The localisation and function of these MAPs are not determined simply by their intrinsic microtubule-binding activity. Instead this family executes its diverse roles by interacting with other regulatory molecules, including microtubule motors and centrosomal proteins. The modular structure of these MAPs may allow them to interact with multiple proteins and thereby be involved in a wide variety of microtubule and spindle functions. Movies available on-line

Sign in / Sign up

Export Citation Format

Share Document