Analysis of mitochondria, endoplasmic reticulum and actin filaments after PDT with AlPcS 4

2004 ◽  
Vol 18 (4) ◽  
pp. 207-212 ◽  
Author(s):  
A. C. Tedesco ◽  
G. Sousa ◽  
R. A. Z�ngaro ◽  
N. S. Silva ◽  
M. T. T. Pacheco ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Actin Filaments

scholarly journals Myosin Motors and Not Actin Comets Are Mediators of the Actin-based Golgi-to-Endoplasmic Reticulum Protein Transport

2003 ◽  
Vol 14 (2) ◽  
pp. 445-459 ◽  
Author(s):  
Juan M. Durán ◽  
Ferran Valderrama ◽  
Susana Castel ◽  
Juana Magdalena ◽  
Mónica Tomás ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Light Chain ◽  
Shiga Toxin ◽  
Actin Filaments ◽  
Protein Transport ◽  
Myosin Ii ◽  
Nonmuscle Myosin ◽  
Nonmuscle Myosin Ii ◽  
Myosin Motors

We have previously reported that actin filaments are involved in protein transport from the Golgi complex to the endoplasmic reticulum. Herein, we examined whether myosin motors or actin comets mediate this transport. To address this issue we have used, on one hand, a combination of specific inhibitors such as 2,3-butanedione monoxime (BDM) and 1-[5-isoquinoline sulfonyl]-2-methyl piperazine (ML7), which inhibit myosin and the phosphorylation of myosin II by the myosin light chain kinase, respectively; and a mutant of the nonmuscle myosin II regulatory light chain, which cannot be phosphorylated (MRLC2AA). On the other hand, actin comet tails were induced by the overexpression of phosphatidylinositol phosphate 5-kinase. Cells treated with BDM/ML7 or those that express the MRLC2AA mutant revealed a significant reduction in the brefeldin A (BFA)-induced fusion of Golgi enzymes with the endoplasmic reticulum (ER). This delay was not caused by an alteration in the formation of the BFA-induced tubules from the Golgi complex. In addition, the Shiga toxin fragment B transport from the Golgi complex to the ER was also altered. This impairment in the retrograde protein transport was not due to depletion of intracellular calcium stores or to the activation of Rho kinase. Neither the reassembly of the Golgi complex after BFA removal nor VSV-G transport from ER to the Golgi was altered in cells treated with BDM/ML7 or expressing MRLC2AA. Finally, transport carriers containing Shiga toxin did not move into the cytosol at the tips of comet tails of polymerizing actin. Collectively, the results indicate that 1) myosin motors move to transport carriers from the Golgi complex to the ER along actin filaments; 2) nonmuscle myosin II mediates in this process; and 3) actin comets are not involved in retrograde transport.

scholarly journals Receptor-mediated Drp1 oligomerization on endoplasmic reticulum

2017 ◽  
Vol 216 (12) ◽  
pp. 4123-4139 ◽  
Author(s):  
Wei-Ke Ji ◽  
Rajarshi Chakrabarti ◽  
Xintao Fan ◽  
Lori Schoenfeld ◽  
Stefan Strack ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Actin Filaments ◽  
Mammalian Cells ◽  
Actin Polymerization ◽  
Mitochondrial Division ◽  
Multiple Factors ◽  
Guanosine Triphosphatase

Drp1 is a dynamin guanosine triphosphatase important for mitochondrial and peroxisomal division. Drp1 oligomerization and mitochondrial recruitment are regulated by multiple factors, including interaction with mitochondrial receptors such as Mff, MiD49, MiD51, and Fis. In addition, both endoplasmic reticulum (ER) and actin filaments play positive roles in mitochondrial division, but mechanisms for their roles are poorly defined. Here, we find that a population of Drp1 oligomers is associated with ER in mammalian cells and is distinct from mitochondrial or peroxisomal Drp1 populations. Subpopulations of Mff and Fis1, which are tail-anchored proteins, also localize to ER. Drp1 oligomers assemble on ER, from which they can transfer to mitochondria. Suppression of Mff or inhibition of actin polymerization through the formin INF2 significantly reduces all Drp1 oligomer populations (mitochondrial, peroxisomal, and ER bound) and mitochondrial division, whereas Mff targeting to ER has a stimulatory effect on division. Our results suggest that ER can function as a platform for Drp1 oligomerization, and that ER-associated Drp1 contributes to mitochondrial division.

Particles Seen in Fefeze-Fracture Preparattoks

1969 ◽  
Vol 27 ◽  
pp. 206-207
Author(s):  
Stanley Bullivant
Keyword(s):  
Endoplasmic Reticulum ◽  
Cardiac Muscle ◽  
Nuclear Membrane ◽  
Actin Filaments ◽  
Carbon Coating ◽  
Freeze Fracture ◽  
Animal Tissues ◽  
Outer Nuclear Membrane ◽  
First Category ◽  
Electron Microscopical

A variety of animal tissues were examined by the simple freeze-fracture technique. An apparatus was used in which the Pt shadowing and carbon coating was carried out through aligned tunnels or apertures. Tn this way the previously fractured cold specimen is protected from contamination.Some particles seen in freeze-fracture replicas can be correlated with structures seen by other electron microscopical techniques. Into this first category fall the broken-off ends of myosin and actin filaments, (Figure 1), the broken-off ends of nucleohistone fibrils the particles seen between membranes in the close junction in cardiac muscle (Figure 2) and quantasomes in chloroplasts. The second group of particles are those found on membranes. An example of these is provided by the membrane faces seen in a fracture through the endoplasmic reticulum (Figure 3). The topology of the situation can be worked out using the outer nuclear membrane as a reference and counting off alternate cytoplasmic and cisternal spaces.

Gelsolin — evidence for a role in turnover of junction-related actin filaments in Sertoli cells

2002 ◽  
Vol 115 (3) ◽  
pp. 499-505 ◽  
Author(s):  
Julian A. Guttman ◽  
Paul Janmey ◽  
A. Wayne Vogl
Keyword(s):  
Endoplasmic Reticulum ◽  
Phospholipase C ◽  
Sertoli Cells ◽  
Actin Filaments ◽  
Synthetic Peptide ◽  
Inositol Triphosphate ◽  
Binding Region ◽  
Phosphoinositide Pathway ◽  
Hydrolysis Of ◽  
Adhesion Complex

The gelsolin-phosphoinositide pathway may be part of the normal mechanism by which Sertoli cells regulate sperm release and turnover of the blood-testis barrier. The intercellular adhesion complexes (ectoplasmic specializations)involved with these two processes are tripartite structures consisting of the plasma membrane, a layer of actin filaments and a cistern of endoplasmic reticulum. Gelsolin is concentrated in these adhesion complexes. In addition,phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) and phosphoinositide-specific phospholipase C are found in the structures. Treatment of isolated spermatid/junction complexes with exogenous phosphoinositide-specific phospholipase C, or with a synthetic peptide consisting of the PtdIns(4,5)P2 binding region of gelsolin, results in the release of gelsolin and loss of actin from the adhesion complexes. We present a model for the disassembly of the actin layer of the adhesion complex that involves the hydrolysis of PtdIns(4,5)P2 resulting in the release of gelsolin within the plaque. Further, we speculate that the hydrolysis of PtdIns(4,5)P2 may result in a local Ca2+ surge via the action of inositol triphosphate on junctional endoplasmic reticulum. This Ca2+ surge would facilitate the actin severing function of gelsolin within the adhesion complex.

scholarly journals The mechanism of cytoplasmic streaming in characean algal cells: sliding of endoplasmic reticulum along actin filaments.

1988 ◽  
Vol 106 (5) ◽  
pp. 1545-1552 ◽  
Author(s):  
B Kachar ◽  
T S Reese
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Actin Filaments ◽  
Cytoplasmic Streaming ◽  
Giant Cells ◽  
Cortical Actin ◽  
Shear Forces ◽  
Actin Cables ◽  
Fast Freezing ◽  
Characean Algae

Electron microscopy of directly frozen giant cells of characean algae shows a continuous, tridimensional network of anastomosing tubes and cisternae of rough endoplasmic reticulum which pervade the streaming region of their cytoplasm. Portions of this endoplasmic reticulum contact the parallel bundles of actin filaments at the interface with the stationary cortical cytoplasm. Mitochondria, glycosomes, and other small cytoplasmic organelles enmeshed in the endoplasmic reticulum network display Brownian motion while streaming. The binding and sliding of endoplasmic reticulum membranes along actin cables can also be directly visualized after the cytoplasm of these cells is dissociated in a buffer containing ATP. The shear forces produced at the interface with the dissociated actin cables move large aggregates of endoplasmic reticulum and other organelles. The combination of fast-freezing electron microscopy and video microscopy of living cells and dissociated cytoplasm demonstrates that the cytoplasmic streaming depends on endoplasmic reticulum membranes sliding along the stationary actin cables. Thus, the continuous network of endoplasmic reticulum provides a means of exerting motive forces on cytoplasm deep inside the cell distant from the cortical actin cables where the motive force is generated.

scholarly journals ER–mitochondria contacts: Actin dynamics at the ER control mitochondrial fission via calcium release

2017 ◽  
Vol 217 (1) ◽  
pp. 15-17 ◽  
Author(s):  
Janos Steffen ◽  
Carla M. Koehler
Keyword(s):  
Endoplasmic Reticulum ◽  
Actin Filaments ◽  
Actin Polymerization ◽  
Calcium Uptake ◽  
Calcium Release ◽  
Mitochondrial Fission ◽  
Actin Dynamics ◽  
Mitochondrial Division ◽  
Cell Biol ◽  
Important Player

The formin-like protein INF2 is an important player in the polymerization of actin filaments. In this issue, Chakrabarti et al. (2018. J. Cell Biol. https://doi.org/10.1083/jcb.201709111) demonstrate that INF2 mediates actin polymerization at the endoplasmic reticulum (ER), resulting in increased ER–mitochondria contacts, calcium uptake by mitochondria, and mitochondrial division.

Endoplasmic reticulum distribution during bovine oocyte activation is regulated by protein kinase C via actin filaments

2020 ◽  
Vol 235 (7-8) ◽  
pp. 5823-5834
Author(s):  
Weber Beringui Feitosa ◽  
Everton Lopes ◽  
Jose Antonio Visintin ◽  
Mayra Elena Ortiz D'Avila Assumpção
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Actin Filaments ◽  
Oocyte Activation ◽  
Bovine Oocyte ◽  
Kinase C
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