Cytoskeleton-secretory vesicle interactions during the docking of secretory vesicles at the cell membrane in Paramecium tetraurelia cells.

International Review of Cytology

Kissmehl

2003

Results achieved in tile molecular biology of Paramecium have shed new light on its elaborate membrane trafficking system. Paramecium disposes not only of the standard routes (endoplasmic reticulum ---+ Golgi ---+ Iysosomes or secretory vesicles; endo-and phagosomes ---+ Iysosomes/digesting vacuoles), but also of some unique features, e.g. and elaborate phagocytic route with the cytoproct and membrane recycling to the cytopharynx, as well as the osmoregulatory system with multiple membrane fusion sites. Exocytosis sites for trichocysts (dense-core secretory vesicles), parasomal sacs (coated pits), and terminal cisternae (early endosomes) display additional regularly arranged predetermined fusion/fission sites, which now can be discussed on a molecular basis. Considering the regular, repetitive arrangements of membrane components, availability of mutants for complementation studies, sensitivity to gene silencing, and so on, Paramecium continues to be a valuable model system for analyzing membrane interactions. This review intends to set a new baseline for ongoing work along these lines.

Section: Microtubules As Long-range Signals For Vesicle Traffickingmentioning

confidence: 80%

Section: Ill Standard Route: Endoplasmic Reticulum To Golgi Complex mentioning

confidence: 99%

Section: Microtubules As Long-range Signals For Vesicle Traffickingmentioning

confidence: 99%

See 1 more Smart Citation

Molecular Aspects of Membrane Trafficking in Paramecium

International Review of Cytology

Kissmehl

2003

“…FM1-43 labeled detached trichocysts are redocked in a saltatory manner, just like "virgin" trichocysts (Aufderheide, 1977), via microtubules emanating from ciliary basal bodies (Plattner, Westphal & Tiggemann, 1982;Glas-Albrecht et al, 1991). In the Results we tried to estimate the time scale of maturation of newly assembled trichocyst docking/fusion sites.…”

Section: Redocking Of Trichocysts and Maturation Of Docking/fusion Sitesmentioning

confidence: 99%

``Frustrated Exocytosis'' — A Novel Phenomenon: Membrane Fusion without Contents Release, Followed by Detachment and Reattachment of Dense Core Vesicles in Paramecium Cells

Klauke

2000

J. Membrane Biol.

Abstract. The lipophilic fluorescent dye, FM1-43, as now frequently used to stain cell membranes and to monitor exo-endocytosis and membrane recycling, induces a cortical [Ca 2+ ] i transient and exocytosis of dense core vesicles ("trichocysts") , for reasons to be elucidated, they are tubular, though both types are endocytosed and lose their FM1-43 stain. In contrast, in presence of [Mg 2+ ] o ‫ס‬ 3 mM (which inhibits contents release), the exocytotic openings reseal and intact trichocysts with labeled membranes and with still condensed contents are detached from the cell surface ("frustrated exocytosis") within ∼15 min. They undergo cytoplasmic streaming and saltatory redocking, with a half-time of ∼35 min. During this time, the population of redocked trichocysts amenable to exocytosis upon a second stimulus increases with a half-time of ∼35 min. Therefore, acquirement of competence for exocytotic membrane fusion may occur with only a small delay after docking, and this maturation process may last only a short time. A similar number of trichocysts can be detached by merely increasing [Mg 2+ ] o to 3 mM, or by application of the anti-calmodulin drug, R21547 (calmidazolium). Essentially we show (i) requirement of calmodulin and appropriate [Me 2+ ] to maintain docking sites in a functional state, (ii) requirement of Ca o 2+ or of some other Me o 2+ to drive membrane resealing during exo-endocytosis, (iii) requirement of an "empty" signal to go to the regular endocytotic pathway (with fading fluorescence), and (iv) occurrence of a "filled" signal for trichocysts to undergo detachment and redocking (with fluorescence) after "frustrated exocytosis".

“…A typical long-range signal is the docking of trichocysts (Aufderheide 1978) along microtubules which emanate from ciliary basal bodies and, thus, serve as transport rails (Plattner et al 1982). This has to be complemented by short-range signals.…”

Section: Long-and Short-range Signalsmentioning

confidence: 99%

Principles of Intracellular Signaling in Ciliated Protozoa—A Brief Outline

Biocommunication of Ciliates

2016

Ciliates have available most of the intracellular signaling mechanisms known from metazoans. Long-range signals are represented by firmly installed microtubules serving as gliding rails aiming at specific targets. Many components are distinctly arranged to guarantee locally restricted effects. Short-range signals include Ca 2+ , provided from different sources, and proteins for membrane recognition and fusion, such as SNAREs, GTPases and high affinity Ca 2+ -binding proteins (still to be defined). A battery of ion conductances serves for electric coupling from the outside medium to specific responses, notably ciliary activity, which also underlies gravitaxis responses. Eventually cyclic nucleotides are involved, e.g. in ciliary signaling. Furthermore, an elaborate system of protein kinases and phosphatases exerts signaling mechanisms in widely different processes.