Microtubular cytoskeleton-based cell outgrowths: from pseudopodia to axons and dendrites

We have recently reported that disruption of the actin cytoskeleton enhanced N-formylmethionyl-leucyl-phenylalanine (fMLP)-stimulated granule exocytosis in human neutrophils but decreased plasma membrane expression of complement receptor 1 (CR1), a marker of secretory vesicles. The present study was initiated to determine if reduced CR1 expression was due to fMLP-stimulated endocytosis, to determine the mechanism of this endocytosis, and to examine its impact on neutrophil functional responses. Stimulation of neutrophils with fMLP or ionomycin in the presence of latrunculin A resulted in the uptake of Alexa fluor 488-labeled albumin and transferrin and reduced plasma membrane expression of CR1. These effects were prevented by preincubation of the cells with sucrose, chlorpromazine, or monodansylcadaverine (MDC), inhibitors of clathrin-mediated endocytosis. Sucrose, chlorpromazine, and MDC also significantly inhibited fMLP- and ionomycin-stimulated specific and azurophil granule exocytosis. Disruption of microtubules with nocodazole inhibited endocytosis and azurophil granule exocytosis stimulated by fMLP in the presence of latrunculin A. Pharmacological inhibition of phosphatidylinositol 3-kinase, ERK1/2, and PKC significantly reduced fMLP-stimulated transferrin uptake in the presence of latrunculin A. Blockade of clathrin-mediated endocytosis had no significant effect on fMLP-stimulated phosphorylation of ERK1/2 in neutrophils pretreated with latrunculin A. From these data, we conclude that the actin cytoskeleton functions to limit microtubule-dependent, clathrin-mediated endocytosis in stimulated human neutrophils. The limitation of clathrin-mediated endocytosis by actin regulates the extent of both specific and azurophilic granule exocytosis.

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The microtubular cytoskeleton and chromosomes of unfertilized human oocytes aged in vitro

Human Genetics ◽

10.1007/bf01790094 ◽

1988 ◽

Vol 80 (3) ◽

pp. 259-264 ◽

Cited By ~ 63

Author(s):

U. Eichenlaub-Ritter ◽

A. Stahl ◽

J. M. Luciani

Keyword(s):

Human Oocytes ◽

Microtubular Cytoskeleton

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Signal-induced reorganization of the microtubular cytoskeleton in the ciliated protozoon Euplotes octocarinatus

Journal of Cell Science ◽

10.1242/jcs.87.4.555 ◽

1987 ◽

Vol 87 (4) ◽

pp. 555-564

Author(s):

MARIA JERKA-DZIADOSZ ◽

CHRISTINE DOSCHE ◽

HANS-WERNER KUHLMANN ◽

KLAUS HECKMANN

Keyword(s):

General Pattern ◽

Dorsal Surface ◽

Cell Cortex ◽

Circular Form ◽

Transmission Electron ◽

Microtubular Cytoskeleton ◽

Subcortical Regions ◽

Cell Changes ◽

Euplotes Octocarinatus ◽

Triton X

A predator-released substance induces the freshwater ciliate Euplotes octocarinatus to undergo, within a few hours, a drastic change in cell form that makes engulfment by the predator more difficult or even impossible. During this transformation, the outline of the cell changes from ovoid to circular and the size increases considerably. The cells cease dividing while they transform, but later continue divisional morphogenesis and maintain the circular form for many cell generations if the concentration of the predator factor is maintained. The microtubular cytoskeleton of Euplotes was studied by transmission electron microscopy of cells from which the cytoplasm had been extracted by mild treatment with Triton X-100. This procedure increased the visibility of microtubules, especially single microtubules located in the endoplasm. In transformed cells, a considerable increase in number of microtubular triads on the dorsal and ventral surfaces and the appearance of extra single microtubules between the dorsal triads was observed. However, certain interconnected groupings of microtubules located on the dorsal surface were greatly diminished after transformation. Intracytoplasmic microtubules were also more abundant in the enlarged cells than in the untreated ovoid ones. The spacing and general pattern of microtubules, however, appears to be the same in untreated and treated cells. We conclude from these observations that the transformation of Euplotes cells from their typical ovoid form into the enlarged circular form is accompanied by the mobilization and utilization of microtubules already present in subcortical regions and an assembly of new microtubules needed for support of the expanding cell cortex.

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Cloning and sequencing of the cyclin-related cdc13+ gene and a cytological study of its role in fission yeast mitosis

Journal of Cell Science ◽

10.1242/jcs.91.4.587 ◽

1988 ◽

Vol 91 (4) ◽

pp. 587-595 ◽

Cited By ~ 5

Author(s):

I. Hagan ◽

J. Hayles ◽

P. Nurse

Keyword(s):

Amino Acids ◽

Protein Kinase ◽

Fission Yeast ◽

Gene Function ◽

Mammalian Cells ◽

Major Part ◽

Cytological Study ◽

Partial Loss ◽

Cloning And Sequencing ◽

Microtubular Cytoskeleton

We have cloned and sequenced the cdc13+ gene from fission yeast. When a major part of the cdc13+ gene is deleted from the chromosome, cells arrest in interphase, but partial loss of gene activity leads to cells containing condensed chromosomes, aberrant septa and a microtubular cytoskeleton with characteristics of both G2 and M. Expression of this phenotype is influenced by the nutritional status of the cell. Our results suggest that the cdc13+ gene function is required for the control of the G2 to M transition. It appears to play a role in regulating the separate pathways of events involved in the physical process of mitosis, for example in the reorganization of the cytoskeleton on transition from G2 to mitosis. The cdc13+ gene function interacts closely with both the yeast and human homologues of cdc2+, suggesting that mammalian cells may contain a cdc13+ homologue. The gene encodes a putative polypeptide of 482 amino acids, and a central region of 176 amino acids of this polypeptide is 50% identical with sea urchin cyclin. Therefore, the cdc13+ protein is cyclin related and could act as a regulator or substrate of the p34cdc2 protein kinase, which initiates mitosis.

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