scholarly journals Stretch magnitude and frequency-dependent actin cytoskeleton remodeling in alveolar epithelia

2010 ◽  
Vol 299 (2) ◽  
pp. C345-C353 ◽  
Author(s):  
Brian C. DiPaolo ◽  
Guillaume Lenormand ◽  
Jeffrey J. Fredberg ◽  
Susan S. Margulies
Keyword(s):  
Plasma Membrane ◽  
Actin Cytoskeleton ◽  
Alveolar Epithelial Cells ◽  
Actin Binding ◽  
Specific Response ◽  
Spontaneous Movement ◽  
Alveolar Epithelial ◽  
Membrane Surfaces ◽  
Cytoskeleton Remodeling ◽  
A Cell

Alveolar epithelial cells (AEC) maintain integrity of the blood-gas barrier with gasket-like intercellular tight junctions (TJ) that are anchored internally to the actin cytoskeleton. We hypothesize that stretch rapidly reorganizes actin (<10 min) into a perijunctional actin ring (PJAR) in a manner that is dependent on magnitude and frequency of the stretch, accompanied by spontaneous movement of actin-anchored receptors at the plasma membrane. Primary AEC monolayers were stretched biaxially to create a change in surface area (ΔSA) of 12%, 25%, or 37% in a cyclic manner at 0.25 Hz for up to 60 min, or held tonic at 25% ΔSA for up to 60 min, or left unstretched. By 10 min of stretch PJARs were evident in 25% and 37% ΔSA at 0.25 Hz, but not for 12% ΔSA at 0.25 Hz, or at tonic 25% ΔSA, or with no stretch. Treatment with 1 μM jasplakinolide abolished stretch-induced PJAR formation, however. As a rough index of remodeling rate, we measured spontaneous motions of 5-μm microbeads bound to actin focal adhesion complexes on the apical membrane surfaces; within 1 min of exposure to ΔSA of 25% and 37%, these motions increased substantially, increased with increasing stretch frequency, and were consistent with our mechanistic hypothesis. With a tonic stretch, however, the spontaneous motion of microbeads attenuated back to unstretched levels, whereas PJAR remained unchanged. Stretch did not increase spontaneous microbead motion in human alveolar epithelial adenocarcinoma A549 monolayers, confirming that this actin remodeling response to stretch was a cell-type specific response. In summary, stretch of primary rat AEC monolayers forms PJARs and rapidly reorganized actin binding sites at the plasma membrane in a manner dependent on stretch magnitude and frequency.

scholarly journals Electron Microscopic Study of the Phagocytosis Process in Lung

1960 ◽  
Vol 7 (2) ◽  
pp. 357-366 ◽  
Author(s):  
H. E. Karrer
Keyword(s):  
Plasma Membrane ◽  
Alveolar Macrophages ◽  
Alveolar Epithelium ◽  
Alveolar Epithelial Cells ◽  
Electron Microscopic ◽  
Double Line ◽  
Alveolar Epithelial ◽  
Culture Cells ◽  
India Ink ◽  
Intracellular Vesicles

Diluted India ink was instilled into the nasal cavity of mice and the lungs of some animals were fixed with osmium tetroxide at various intervals after one instillation. The lungs of other animals were fixed after 4, 7, 9, 16, or 18 daily instillations. The India ink was found to be phagocytized almost exclusively by the free alveolar macrophages. A few particles are occasionally seen within thin portions of alveolar epithelium, within the "small" alveolar epithelial cells, or within occasional leukocytes in the lumina of alveoli. The particles are ingested by an invagination process of the plasma membrane resulting in the formation of intracellular vesicles and vacuoles. Ultimately large amounts of India ink accumulate in the cell, occupying substantial portions of the cytoplasm. The surfaces of phagocytizing macrophages show signs of intense motility. Their cytoplasm contains numerous particles, resembling Palade particles, and a large amount of rough surfaced endoplasmic reticulum. These structures are interpreted as indicative of protein synthesis. At the level of resolution achieved in this study the membranes of this reticulum appear as single dense "lines." On the other hand, the plasma membrane and the limiting membranes of vesicles and of vacuoles often exhibit the double-line structure typical of unit membranes (Robertson, 37). The inclusion bodies appear to be the product of phagocytosis. It is believed that some of them derive from the vacuoles mentioned above, and that they correspond to similar structures seen in phase contrast cinemicrographs of culture cells. Their matrix represents phagocytized material. Certain structures within this matrix are considered as secondary and some of these structures possess an ordered form probably indicative of the presence of lipid. The possible origin and the fate of alveolar macrophages are briefly discussed.

scholarly journals Ultrastructure of the yeast actin cytoskeleton and its association with the plasma membrane.

1994 ◽  
Vol 125 (2) ◽  
pp. 381-391 ◽  
Author(s):  
J Mulholland ◽  
D Preuss ◽  
A Moon ◽  
A Wong ◽  
D Drubin ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Actin Cytoskeleton ◽  
Binding Proteins ◽  
Ultrastructural Level ◽  
Actin Binding ◽  
Cortical Actin ◽  
Actin Binding Proteins ◽  
Double Labeling ◽  
Wall Growth ◽  
Cortical Cytoskeleton

We characterized the yeast actin cytoskeleton at the ultrastructural level using immunoelectron microscopy. Anti-actin antibodies primarily labeled dense, patchlike cortical structures and cytoplasmic cables. This localization recapitulates results obtained with immunofluorescence light microscopy, but at much higher resolution. Immuno-EM double-labeling experiments were conducted with antibodies to actin together with antibodies to the actin binding proteins Abp1p and cofilin. As expected from immunofluorescence experiments, Abp1p, cofilin, and actin colocalized in immuno-EM to the dense patchlike structures but not to the cables. In this way, we can unambiguously identify the patches as the cortical actin cytoskeleton. The cortical actin patches were observed to be associated with the cell surface via an invagination of plasma membrane. This novel cortical cytoskeleton-plasma membrane interface appears to consist of a fingerlike invagination of plasma membrane around which actin filaments and actin binding proteins are organized. We propose a possible role for this unique cortical structure in wall growth and osmotic regulation.

scholarly journals Molecular basis for coupling the plasma membrane to the actin cytoskeleton during clathrin-mediated endocytosis

2012 ◽  
Vol 109 (38) ◽  
pp. E2533-E2542 ◽  
Author(s):  
Michal Skruzny ◽  
Thorsten Brach ◽  
Rodolfo Ciuffa ◽  
Sofia Rybina ◽  
Malte Wachsmuth ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Actin Cytoskeleton ◽  
Actin Filaments ◽  
Lipid Binding ◽  
Actin Binding ◽  
Dependent Manner ◽  
Vesicle Budding ◽  
Cooperative Action ◽  
Binding Domains ◽  
Membrane Invagination

Dynamic actin filaments are a crucial component of clathrin-mediated endocytosis when endocytic proteins cannot supply enough energy for vesicle budding. Actin cytoskeleton is thought to provide force for membrane invagination or vesicle scission, but how this force is transmitted to the plasma membrane is not understood. Here we describe the molecular mechanism of plasma membrane–actin cytoskeleton coupling mediated by cooperative action of epsin Ent1 and the HIP1R homolog Sla2 in yeast Saccharomyces cerevisiae. Sla2 anchors Ent1 to a stable endocytic coat by an unforeseen interaction between Sla2’s ANTH and Ent1’s ENTH lipid-binding domains. The ANTH and ENTH domains bind each other in a ligand-dependent manner to provide critical anchoring of both proteins to the membrane. The C-terminal parts of Ent1 and Sla2 bind redundantly to actin filaments via a previously unknown phospho-regulated actin-binding domain in Ent1 and the THATCH domain in Sla2. By the synergistic binding to the membrane and redundant interaction with actin, Ent1 and Sla2 form an essential molecular linker that transmits the force generated by the actin cytoskeleton to the plasma membrane, leading to membrane invagination and vesicle budding.

Deformation-induced lipid trafficking in alveolar epithelial cells

2001 ◽  
Vol 280 (5) ◽  
pp. L938-L946 ◽  
Author(s):  
Nicholas E. Vlahakis ◽  
Mark A. Schroeder ◽  
Richard E. Pagano ◽  
Rolf D. Hubmayr
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Membrane Trafficking ◽  
Wound Repair ◽  
Alveolar Epithelial Cells ◽  
Fluorescent Properties ◽  
Lipid Trafficking ◽  
Alveolar Epithelial ◽  
Injury And Repair

Mechanical ventilation with a high tidal volume results in lung injury that is characterized by blebbing and breaks both between and through alveolar epithelial cells. We developed an in vitro model to simulate ventilator-induced deformation of the alveolar basement membrane and to investigate, in a direct manner, epithelial cell responses to deforming forces. Taking advantage of the novel fluorescent properties of BODIPY lipids and the fluorescent dye FM1-43, we have shown that mechanical deformation of alveolar epithelial cells results in lipid transport to the plasma membrane. Deformation-induced lipid trafficking (DILT) was a vesicular process, rapid in onset, and was associated with a large increase in cell surface area. DILT could be demonstrated in all cells; however, only a small percentage of cells developed plasma membrane breaks that were reversible and nonlethal. Therefore, DILT was not only involved in site-directed wound repair but might also have served as a cytoprotective mechanism against plasma membrane stress failure. This study suggests that DILT is a regulatory mechanism for membrane trafficking in alveolar epithelia and provides a novel biological framework within which to consider alveolar deformation injury and repair.

Mechanical stretching of alveolar epithelial cells increases Na+-K+-ATPase activity

1999 ◽  
Vol 87 (2) ◽  
pp. 715-721 ◽  
Author(s):  
Christopher M. Waters ◽  
Karen M. Ridge ◽  
G. Sunio ◽  
K. Venetsanou ◽  
Jacob Iasha Sznajder
Keyword(s):  
Epithelial Cells ◽  
Atpase Activity ◽  
Basolateral Membrane ◽  
Alveolar Epithelial Cells ◽  
Lung Epithelial Cells ◽  
Cyclic Stretch ◽  
Lung Edema ◽  
Alveolar Epithelial ◽  
A Cell

Alveolar epithelial cells effect edema clearance by transporting Na+ and liquid out of the air spaces. Active Na+ transport by the basolaterally located Na+-K+-ATPase is an important contributor to lung edema clearance. Because alveoli undergo cyclic stretch in vivo, we investigated the role of cyclic stretch in the regulation of Na+-K+-ATPase activity in alveolar epithelial cells. Using the Flexercell Strain Unit, we exposed a cell line of murine lung epithelial cells (MLE-12) to cyclic stretch (30 cycles/min). After 15 min of stretch (10% mean strain), there was no change in Na+-K+-ATPase activity, as assessed by86Rb+uptake. By 30 min and after 60 min, Na+-K+-ATPase activity was significantly increased. When cells were treated with amiloride to block amiloride-sensitive Na+ entry into cells or when cells were treated with gadolinium to block stretch-activated, nonselective cation channels, there was no stimulation of Na+-K+-ATPase activity by cyclic stretch. Conversely, cells exposed to Nystatin, which increases Na+ entry into cells, demonstrated increased Na+-K+-ATPase activity. The changes in Na+-K+-ATPase activity were paralleled by increased Na+-K+-ATPase protein in the basolateral membrane of MLE-12 cells. Thus, in MLE-12 cells, short-term cyclic stretch stimulates Na+-K+-ATPase activity, most likely by increasing intracellular Na+ and by recruitment of Na+-K+-ATPase subunits from intracellular pools to the basolateral membrane.

scholarly journals Tobacco WLIM1 Is a Novel F-Actin Binding Protein Involved in Actin Cytoskeleton Remodeling

2006 ◽  
Vol 18 (9) ◽  
pp. 2194-2206 ◽  
Author(s):  
Clément Thomas ◽  
Céline Hoffmann ◽  
Monika Dieterle ◽  
Marleen Van Troys ◽  
Christophe Ampe ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Binding Protein ◽  
Actin Binding ◽  
Actin Binding Protein ◽  
Cytoskeleton Remodeling

ICAM-1 facilitates alveolar macrophage phagocytic activity through effects on migration over the AEC surface

2002 ◽  
Vol 283 (1) ◽  
pp. L180-L187 ◽  
Author(s):  
Robert Paine ◽  
Susan B. Morris ◽  
Hong Jin ◽  
Carlos E. O. Baleeiro ◽  
Steven E. Wilcoxen
Keyword(s):  
Actin Cytoskeleton ◽  
Phagocytic Activity ◽  
Cytochalasin B ◽  
Alveolar Epithelial Cells ◽  
Intercellular Adhesion Molecule ◽  
Type I ◽  
Wild Type ◽  
Intercellular Adhesion Molecule 1 ◽  
Alveolar Epithelial ◽  
Deficient Mice

We postulate that intercellular adhesion molecule-1 (ICAM-1) on type I alveolar epithelial cells (AEC) facilitates phagocytic activity of alveolar macrophages (AM) in the alveolus. When wild-type and ICAM-1-deficient mice were inoculated intratracheally with FITC-labeled microspheres, AM phagocytosis of beads (after 1 and 4 h) was significantly reduced in ICAM-1−/− mice compared with controls. To focus on ICAM-1-mediated interactions specifically involving AM and AEC, rat AM were placed in culture with rat AEC treated with neutralizing anti-ICAM-1 F(ab′)2fragments. Blocking ICAM-1 significantly decreased the AM phagocytosis of beads. Planar chemotaxis of AM over the surface of AEC was also significantly impaired by neutralization of AEC ICAM-1. ICAM-1 in rat AEC is associated with the actin cytoskeleton. Planar chemotaxis of AM was also significantly reduced by pretreatment of the AEC monolayer with cytochalasin B to disrupt the actin cytoskeleton. These studies indicate that ICAM-1 on the AEC surface promotes mobility of AM in the alveolus and is critically important for the efficient phagocytosis of particulates by AM.

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