The roles of actin cytoskeleton and microtubules for membrane recycling of a food vacuole inTetrahymena thermophila

Exocytosis and membrane recycling at the cytoproct (cell anus) of Tetrahymena pyriformis were studied using thin-section electron microscopy. Single cells were fixed at specific times relative to the elimination of the vacuole's contents—before elimination, at elimination, 3–5 s and 10–15 s following elimination. The closed cytoproct is distinguished from other pellicular regions by a single membrane at the cell surface which is circumscribed by an electron-opaque flange that links or welds the plasma membrane to the underlying alveolar margins. Microtubules originating in the flange pass inward where they lie over, and possibly guide, the approaching food vacuoles to the cytoproct. Food facuoles near the cytoproct are also accompanied by coats of microfilaments. These microfilaments appear to be active in the channelling and endocytosis of food vacuole membrane. Upon cytoproct opening the plasma membrane and food vacuole membrane fuse. Elimination seems to be essentially passive and is accomplished by re-engulfment of the old food vacuole membrane which is constantly associated with microfilaments. Reengulfment of all the food vacuole membrane requires 10–15 s and results in a closed cytoproct. The membrane remnants embedded in microfilaments form a cluster under the closed cytoproct. At the periphery of this cluster remnants take the shape of 70–130-nm spherical vesicles or 0.2-micrometer-long flattened vesicles.

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Sustained Food Vacuole Formation by AxenicParamecium tetraureliaand the Inhibition of Membrane Recycling by Alcian Blue

The Journal of Protozoology ◽

10.1111/j.1550-7408.1992.tb04453.x ◽

1992 ◽

Vol 39 (6) ◽

pp. 713-718 ◽

Cited By ~ 2

Author(s):

EDNA S. KANESHIRO ◽

STEVEN F. REUTER ◽

FRANK J. QUATTRONE ◽

RANDAL E. MORRIS

Keyword(s):

Alcian Blue ◽

Food Vacuole ◽

Membrane Recycling ◽

Vacuole Formation

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EFA6, a sec7 domain-containing exchange factor for ARF6, coordinates membrane recycling and actin cytoskeleton organization

The EMBO Journal ◽

10.1093/emboj/18.6.1480 ◽

1999 ◽

Vol 18 (6) ◽

pp. 1480-1491 ◽

Cited By ~ 214

Author(s):

M. Franco

Keyword(s):

Actin Cytoskeleton ◽

Membrane Recycling ◽

Exchange Factor ◽

Cytoskeleton Organization ◽

Actin Cytoskeleton Organization ◽

Sec7 Domain

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Exocytosis, endocytosis and membrane recycling in Tetrahymena thermophila

Journal of Cell Science ◽

10.1242/jcs.89.4.515 ◽

1988 ◽

Vol 89 (4) ◽

pp. 515-520

Author(s):

ARNO TIEDTKE ◽

PETER HÜNSELER ◽

JORGE FLORIN-CHRISTENSEN ◽

MONICA FLORIN-CHRISTENSEN

Keyword(s):

Cell Lines ◽

Tetrahymena Thermophila ◽

Food Vacuole ◽

Secondary Effect ◽

Membrane Recycling ◽

Acid Hydrolase ◽

Wild Type ◽

Acid Hydrolases ◽

Vacuole Formation ◽

Food Vacuoles

Mutant and wild-type cell lines of Tetrahymena thermophila were used to investigate a possible connection between acid hydrolase secretion and the major processes through which membranes are recycled in this ciliated protozoon. These processes consist of food vacuole formation (endocytosis), and food vacuole egestion and mucocyst release (both exocytosis). We have found that a mutant (MS-1, see−) blocked in hydrolase secretion is not blocked in either food vacuole formation or egestion and that it has normal mucocyst exocytosis. Another line of experiments with wild-type cells showed also that hydrolase secretion and endocytosis are independent of each other. Thus, sucrose (0.1m) did not interfere with hydrolase secretion, but blocked food vacuole formation. Furthermore, release of acid hydrolases was selectively stimulated by dibucaine without any effect on food vacuole egestion. Finally, exocytosis of mucocysts could occur without simultaneous release of acid hydrolases, as when cells were exposed to (0.15M-NaCl, which evokes a massive secretory response of mucocysts. Our results demonstrate that formation and egestion of food vacuoles and exocytosis of mucocysts are unrelated to secretion of acid hydrolases. Furthermore, they suggest that secretion of acid hydrolases is not a secondary effect of membrane recycling through these processes.

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A role for the actin cytoskeleton in the hormonal and growth-factor-mediated activation of protein kinase B

Biochemical Journal ◽

10.1042/0264-6021:3530735v ◽

2001 ◽

Vol 353 (3) ◽

pp. 735

Author(s):

K. PEYROLLIER ◽

E. HAJDUCH ◽

A. GRAY ◽

G. J. LITHERLAND ◽

A. R. PRESCOTT ◽

...

Keyword(s):

Growth Factor ◽

Protein Kinase ◽

Actin Cytoskeleton ◽

Protein Kinase B

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Spatial control of actin-based motility through plasmalemmal PtdIns(4,5)P2-rich raft assemblies.

Biochemical Society Symposium ◽

10.1042/bss0720119 ◽

2005 ◽

Vol 72 ◽

pp. 119-127 ◽

Cited By ~ 19

Author(s):

Tamara Golub ◽

Caroni Pico

Keyword(s):

Protein Kinase ◽

Cell Surface ◽

Actin Cytoskeleton ◽

Lipid Rafts ◽

Patch Clustering ◽

Pkc Protein Kinase C ◽

Membrane Bound ◽

And Function ◽

Cytoskeleton Dynamics ◽

Syndrome Protein

The interactions of cells with their environment involve regulated actin-based motility at defined positions along the cell surface. Sphingolipid- and cholesterol-dependent microdomains (rafts) order proteins at biological membranes, and have been implicated in most signalling processes at the cell surface. Many membrane-bound components that regulate actin cytoskeleton dynamics and cell-surface motility associate with PtdIns(4,5)P2-rich lipid rafts. Although raft integrity is not required for substrate-directed cell spreading, or to initiate signalling for motility, it is a prerequisite for sustained and organized motility. Plasmalemmal rafts redistribute rapidly in response to signals, triggering motility. This process involves the removal of rafts from sites that are not interacting with the substrate, apparently through endocytosis, and a local accumulation at sites of integrin-mediated substrate interactions. PtdIns(4,5)P2-rich lipid rafts can assemble into patches in a process depending on PtdIns(4,5)P2, Cdc42 (cell-division control 42), N-WASP (neural Wiskott-Aldrich syndrome protein) and actin cytoskeleton dynamics. The raft patches are sites of signal-induced actin assembly, and their accumulation locally promotes sustained motility. The patches capture microtubules, which promote patch clustering through PKA (protein kinase A), to steer motility. Raft accumulation at the cell surface, and its coupling to motility are influenced greatly by the expression of intrinsic raft-associated components that associate with the cytosolic leaflet of lipid rafts. Among them, GAP43 (growth-associated protein 43)-like proteins interact with PtdIns(4,5)P2 in a Ca2+/calmodulin and PKC (protein kinase C)-regulated manner, and function as intrinsic determinants of motility and anatomical plasticity. Plasmalemmal PtdIns(4,5)P2-rich raft assemblies thus provide powerful organizational principles for tight spatial and temporal control of signalling in motility.

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