Progressive and spatially differentiated stability of microtubules in developing neuronal cells.

Lim, Soo-Siang; Sammak, Paul J.; Borisy, Gary G.

doi:10.1083/jcb.109.1.253

Cited by 165 publications

(115 citation statements)

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“…First, the polymer with the highest content of tau is located in the distal part of the axon and in the growth cone. This polymer is also among the most dynamic of the entire axon as measured by its turnover behavior (Lim et al, 1989;Edson et al, 1993;Li and Black, 1996), its relative content of tyrosinated cr-tubulin (Brown et al, 1992), and its sensitivity to MT depolymerizing drugs . Second, the distribution of tubulin between monomer and polymer is similar in the proximal and distal parts of the axon, in spite of the severalfold difference in the amount of total tau relative to total tubulin and in the tau content of the MT polymer in these regions.…”

Section: Discussionmentioning

confidence: 99%

“…Specifically, the polymer located distally near the growth cone turns over more rapidly and is more sensitive to treatments with MT depolymerizing drugs than the polymer situated elsewhere in the axon (Lim et al, 1989;Brown et al, 1992;Ahmad et al, 1993;Baas et al, 1993;Edson et al, 1993;Li and Black, 1996). This naturally occurring spatial variation in the stability properties of MTs in growing axons must reflect a corresponding variation in the factors that promote MT stability.…”

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Tau Is Enriched on Dynamic Microtubules in the Distal Region of Growing Axons

et al. 1996

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It is widely held that tau determines the stability of microtubules in growing axons, although direct evidence supporting this hypothesis is lacking. Previous studies have shown that the microtubule polymer in the distal axon and growth cone is the most dynamic of growing axons; it turns over more rapidly and is more sensitive to microtubule depolymerizing drugs than the polymer situated proximally. We reasoned that if the stability of axonal microtubules is directly related to their content of tau, then the polymer in the distal axon should have less tau than the polymer in the proximal axon. We tested this proposition by measuring the relative tau content of microtubules along growing axons of cultured sympathetic neurons immunostained for tau and tubulin. Our results show that the tau content of microtubules varies along the axon, but in the opposite way predicted. Specifically, the relative tau content of microtubules increases progressively along the axon to reach a peak near the growth cone that is severalfold greater than that observed proximally. Thus, tau is most enriched on the most dynamic polymer of the axon. We also show that the gradient in tau content of microtubules does not generate corresponding gradients in the extent of tubulin assembly or in the sensitivity of axonal microtubules to nocodazole. On the basis of these findings, we propose that tau in growing axons has functions other than promoting microtubule assembly and stability and that key sites for these functions are the distal axon and growth cone.Key words: microtubule-associated proteins; cytoskeleton; axon growth; quantitative digital image analysis; cultured sympathetic neurons Tau is a developmentally regulated microtubule-associated protein (MAP). Tau is encoded by a single gene, but because of alternative splicing and phosphorylation, it shows multiple isoforms (for review, see Wiche et al., 1991). During neuronal differentiation tau undergoes a transition from immature to mature forms that involves a dramatic increase in the number of isoforms (for review, see Schoenfeld and Obar, 1994). A role for tau in axon growth was initially suggested by studies that demonstrated a temporal correlation between the expression of tau, microtubule (MT) assembly, and axon extension (Drubin et al., 1985). More recently, studies that have altered tau expression either upward or downward have reinforced the view that tau participates in axon growth. Specifically, suppressing tau expression can prevent axon growth, whereas overexpressing tau can promote the elaboration of neurite-like processes that contain arrays of parallel MTs in cells that normally do not elaborate such processes (for review, see Hirokawa, 1994).Although the importance of tau in axon growth is well established, its specific functions are unknown. Because tau binds MTs, its functions presumably involve, at least in part, binding to MTs. On the basis of its ability to promote MT assembly and stability in vitro, tau has been proposed to promote MT assembly and stabilization in ...

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Section: Discussionmentioning

confidence: 99%

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Tau Is Enriched on Dynamic Microtubules in the Distal Region of Growing Axons

et al. 1996

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“…In contrast, tubulin is deacetylated in the leading edge of migrating fibroblasts and neuronal growth cones. 13,14 Hyperacetylated microtubules decreased microtubule dynamics, increased microtubule stability and decreased cell migration. 15 Therefore, tubulin acetylation/deacetylation is implicated in the control of microtubule function and, therefore, the regulatory mechanism of tubulin acetylation/deacetylation by acetylase/deacetylase has attracted much attention.…”

Section: Sirt2 and Endothelial Microtubule Reorganization A Hashimotomentioning

confidence: 99%

Angiotensin II induces microtubule reorganization mediated by a deacetylase SIRT2 in endothelial cells

et al. 2011

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Angiotensin II has been implicated in vascular remodeling. Microtubule composed of tubulins regulates cell shape, migration and survival. Tubulin acetylation has an important role in the control of microtubule structure and microtubule-based cellular functions. In this study, angiotensin II induced disassembly and deacetylation of a-tubulin, which were blocked by pretreatment with an angiotensin II type 1 receptor blocker losartan and a sirtuin class deacetylase inhibitor sirtinol, and by depletion of a deacetylase SIRT2 using RNA interference. We investigated the involvement of SIRT2 in angiotensin II-induced endothelial cell migration using the Boyden chamber method. Angiotensin II caused a significant increase in cell migration, which was blocked by pretreatment with sirtinol and SIRT2 depletion. It has been reported that angiotensin II is involved in cytoskeletal reorganization stimulated by mechanical stretch in endothelial cells. We also demonstrated that endothelial cells subjected to a 10% uniaxial stretch showed vertical alignment to the direction of tension and tubulin deacetylation in the peripheral side of cells, in comparison with control static cells. The mechanical stretch-induced changes of microtubules were blocked by pretreatment with sirtinol and SIRT2 depletion. Immunofluorescence microscopy showed that acetylated tubulin was decreased in platelet-endothelial cell adhesion molecule-1-positive cells in the intima of the aortic walls in mice loaded with angiotensin II, in comparison with mice loaded with control vehicle. These data show that angiotensin II and mechanical stretch stimulate microtubule redistribution and deacetylation via SIRT2 in endothelial cells, suggesting the emerging role of SIRT2 in hypertension-induced vascular remodeling.

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“…The continual rearrangement of MTs (or MT ends) that arises as a direct consequence of rapid turnover may be particularly useful in accommodating the cell-shape changes associated with morphogenesis and cell motility (Kirschner and Mitchison, 1986;Sammak and Borisy, 1988b). However, some individual MTs as well as some MT assemblies are extremely stable and turn over with half times of hours, not minutes (Webster et al, 1987b;Webster and Borisy, 1989;Lim et al, 1989). In addition, 1987).…”

Section: Introductionmentioning

confidence: 99%

Detyrosination of alpha tubulin does not stabilize microtubules in vivo [published erratum appears in J Cell Biol 1990 Sep;111(3):1325-6]

Webster

Wehland

Weber

et al. 1990

The Journal of Cell Biology

141

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Abstract.The relationship between alpha tubulin detyrosination and microtubule (MT) stability was examined directly in cultured fibroblasts by experimentally converting the predominantly tyrosinated MT array to a detyrosinated (Glu) array and then assaying MT stability. MTs in mouse Swiss 3T3 cells displayed an increase in Glu immunostaining fluorescence ~1 h after microinjecting antibodies to the tyrosinating enzyme, tubulin tyrosine ligase. Detyrosination progressed to virtual completion after 12 h and persisted for 30-35 h before tyrosinated subunits within MTs were again detected. The stability of these experimentally detyrosinated MTs was tested by first injecting either biotinylated or Xrhodamine-labeled tubulin and then measuring bulk turnover by hapten-mediated immunocytochemistry or fluorescence recovery after photobleaching, respectively. By both methods, turnover was found to be similarly rapid, possessing a half time of ,'~ 3 min. As a final test of MT stability, the level of acetylated tubulin staining in antibody-injected cells was compared with that observed in adjacent, uninjected cells and also with the staining observed in cells whose MTs had been stabilized with taxol. Although intense Glu staining was observed in both injected and taxol-treated cells, increased acetylated tubulin staining was observed only in the taxol-stabilized MTs, indicating that the MTs were not stabilized by detyrosination. Together, these results demonstrated clearly that detyrosination does not directly confer stability on MTs. Therefore, the stable MTs observed in these and other cell lines must have arisen by another mechanism, and may have become posttranslationally modified after their stabilization.

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Progressive and spatially differentiated stability of microtubules in developing neuronal cells.

Cited by 165 publications

References 60 publications

Tau Is Enriched on Dynamic Microtubules in the Distal Region of Growing Axons

Tau Is Enriched on Dynamic Microtubules in the Distal Region of Growing Axons

Angiotensin II induces microtubule reorganization mediated by a deacetylase SIRT2 in endothelial cells

Detyrosination of alpha tubulin does not stabilize microtubules in vivo [published erratum appears in J Cell Biol 1990 Sep;111(3):1325-6]

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