scholarly journals Collagen remodeling by phagocytosis is determined by collagen substrate topology and calcium-dependent interactions of gelsolin with nonmuscle myosin IIA in cell adhesions

2013 ◽  
Vol 24 (6) ◽  
pp. 734-747 ◽  
Author(s):  
P. D. Arora ◽  
Y. Wang ◽  
A. Bresnick ◽  
J. Dawson ◽  
P. A. Janmey ◽  
...  
Keyword(s):  
Focal Adhesions ◽  
Collagen Degradation ◽  
Ion Concentration ◽  
Nonmuscle Myosin ◽  
Collagen Substrate ◽  
Calcium Dependent ◽  
Intracellular Calcium Ion ◽  
Myosin Iia ◽  
Collagen Phagocytosis ◽  
Intracellular Collagen

We examine how collagen substrate topography, free intracellular calcium ion concentration ([Ca2+]i, and the association of gelsolin with nonmuscle myosin IIA (NMMIIA) at collagen adhesions are regulated to enable collagen phagocytosis. Fibroblasts plated on planar, collagen-coated substrates show minimal increase of [Ca2+]i, minimal colocalization of gelsolin and NMMIIA in focal adhesions, and minimal intracellular collagen degradation. In fibroblasts plated on collagen-coated latex beads there are large increases of [Ca2+]i, time- and Ca2+-dependent enrichment of NMMIIA and gelsolin at collagen adhesions, and abundant intracellular collagen degradation. NMMIIA knockdown retards gelsolin recruitment to adhesions and blocks collagen phagocytosis. Gelsolin exhibits tight, Ca2+-dependent binding to full-length NMMIIA. Gelsolin domains G4–G6 selectively require Ca2+ to interact with NMMIIA, which is restricted to residues 1339–1899 of NMMIIA. We conclude that cell adhesion to collagen presented on beads activates Ca2+ entry and promotes the formation of phagosomes enriched with NMMIIA and gelsolin. The Ca2+ -dependent interaction of gelsolin and NMMIIA in turn enables actin remodeling and enhances collagen degradation by phagocytosis.

The influence of methylmercury on the nitric oxide production of alveolar macrophages

2008 ◽  
Vol 24 (8) ◽  
pp. 531-538 ◽  
Author(s):  
TC Kuo
Keyword(s):  
Nitric Oxide ◽  
Adenylate Cyclase ◽  
Alveolar Macrophages ◽  
Ion Concentration ◽  
Nitric Oxide Production ◽  
Calcium Dependent ◽  
Oxide Production ◽  
Extracellular Signal ◽  
Intracellular Calcium Ion ◽  
Living Organisms

Mercury is a global pollutant considered to be a persistent bioaccumulative and toxic chemical. Humans may be exposed to organic forms of mercury by either inhalation, oral, or dermal routes. Methylmercury is more toxic to living organisms than the inorganic forms. In this study, we attempted to elucidate the altered functions of alveolar macrophage including nitric oxide production after methylmercury exposure. Treatment of 7 μM methylmercury for 24 h inhibited lipopolysaccharide-induced nitric oxide and nitric oxide synthase production of alveolar macrophages. The addition of H-89 (PKA inhibitor) significantly decreased the methylmercury inhibition of lipopolysaccharide-mediated nitric oxide production. We found the cell had a calcium-dependent adenylate cyclase, and MeHg could inhibit the phosphorylation of extracellular-signal regulated kinase (ERK). Because methylmercury could increase the intracellular calcium ion concentration, it might activate the adenylate cyclase by increasing [Ca2+]i. Though the interaction of methylmercury with the immune system has been studied by several investigators, the actual mechanisms underlying these interactions are still poorly understood. We discovered that methylmercury could activate protein kinase A, which in turn would inhibit the activation of Raf-1-ERK and so inhibit the release of nitric oxide.

Methylmercury Induces Alveolar Macrophages Apoptosis

2008 ◽  
Vol 27 (3) ◽  
pp. 257-263 ◽  
Author(s):  
Tsun-Cheng Kuo
Keyword(s):  
Calcium Ions ◽  
Alveolar Macrophages ◽  
Inhibitory Effect ◽  
Ion Concentration ◽  
Dna Ladder ◽  
Calcium Dependent ◽  
Ph Values ◽  
Similar Inhibitory Effect ◽  
Intracellular Calcium Ion ◽  
Calcium Ion Concentration

Through the use of a scanning electronic microscope, it was found that alveolar macrophages treated with 10 μM of methylmercury for 24 h showed a decrease of surface microvilli, and those treated with 15 μM of methylmercury underwent deformity and subsequent cell death. To investigate their death patterns, DNA was aspirated from alveolar macrophages and analyzed by electrophoresis. It was discovered that the DNA ladder phenomenon became more obvious as the methylmercury increased in concentration. When 5 mM EGTA was used to eliminate calcium ions, a decrease of the ladder phenomenon was observed. Zinc at 1 mM had a similar inhibitory effect. Moreover, an apoptosis peak was observed on flow cytometry analysis of DNA stained with propidium iodide. Alveolar macrophages stained with Hoechst 33342 demonstrated apoptotic bodies induced by methylmercury. The above data indicate that methylmercury can induce a typical apoptosis in alveolar macrophages. Continuing onto the study of the mechanism of apoptosis as induced by methylmercury in alveolar macrophages, it was discovered that methylmercury could increase the intracellular calcium ion concentration and decrease the pH in alveolar macrophages. To find out which endonuclease was responsible for the methylmercury-induced DNA fragmentation of alveolar macrophages, the nuclear proteins of alveolar macrophages was aspirated and tested under different pH values and in conditions with or without calcium ions, and it was discovered that the endonuclease was calcium dependent without relations to pH values.

Correlation of dysfunction of nonmuscle myosin IIA with increased induction of Cyp1a1 in Hepa-1 cells

2011 ◽  
Vol 1809 (3) ◽  
pp. 176-183 ◽  
Author(s):  
Masayuki Ebina ◽  
Masahiko Shibazaki ◽  
Kyoko Kudo ◽  
Shuya Kasai ◽  
Hideaki Kikuchi
Keyword(s):  
Nonmuscle Myosin ◽  
Myosin Iia

Cloning and developmental expression of nonmuscle myosin IIA (Myh9) in the mammalian inner ear

2004 ◽  
Vol 76 (3) ◽  
pp. 296-305 ◽  
Author(s):  
Anand N. Mhatre ◽  
Jiang Li ◽  
Yuil Kim ◽  
Donald E. Coling ◽  
Anil K. Lalwani
Keyword(s):  
Inner Ear ◽  
Developmental Expression ◽  
Nonmuscle Myosin ◽  
Myosin Iia

Influence of the Membrane Potential on the Intracellular Light Induced Ca2+ -Concentration Change of the Limulus Ventral Photoreceptor Monitored by Arsenazo III under Voltage Clamp Conditions

1984 ◽  
Vol 39 (9-10) ◽  
pp. 986-992 ◽  
Author(s):  
I. Ivens ◽  
H. Stieve
Keyword(s):  
Voltage Clamp ◽  
Light Flash ◽  
Membrane Voltage ◽  
Ion Concentration ◽  
Arsenazo Iii ◽  
Substantial Part ◽  
Voltage Range ◽  
Intracellular Ca ◽  
Intracellular Calcium Ion ◽  
Pass Through

Abstract The light induced transmission change (Arsenazo signal) of an Arsenazo III injected ventral photoreceptor cell of Limulus polyphemus was studied under voltage clamp. The transmission change which represents a change of free intracellular calcium ion concentration, [Ca2+]i, was investigated for its dependence upon membrane voltage. The peak amplitude of the Arsenazo signal decreases in a linear fashion with the clamp voltage in the examined voltage range (from -80 to + 40 mV). In low Ca2+ saline ([Ca2+]e = 250 μᴍ) this decrease in the amplitude of the Arsenazo signal was more pronounced, while in saline with increased Ca2+ ([Ca2+]e = 40, 50 and 100 mᴍ), there is almost no change of the Arsenazo signal with varied membrane voltage. The recovery of the Arsenazo signal (i.e. recovery of the transmission back to the value before the light flash) is faster during hyperpolarization, this recovery being slowed down when the cell is depolarized. From these experiments it is concluded that a substantial part of the Arsenazo signal is due to a light induced influx of Ca2+ from the extracellular space across the cell membrane into the cytoplasma. Conceivably the Ca2+ could pass through light activated Na+ channels. Subsequently the increased intracellular Ca2+ is lowered to the preillumination level, by a membrane voltage dependent mechanism possibly an Na+-Ca2+ exchange. The data do not exclude the possibility that a part of the Ca2+ responsible for the Arsenazo signal is released from intracellular stores.

Stimulus-Dependent Alterations in Quantal Neurotransmitter Release

2006 ◽  
Vol 96 (6) ◽  
pp. 3082-3087 ◽  
Author(s):  
Chad P. Grabner ◽  
Aaron P. Fox
Keyword(s):  
Neurotransmitter Release ◽  
Chromaffin Cells ◽  
Time Course ◽  
Ion Concentration ◽  
Fusion Pore ◽  
Release Process ◽  
Large Dense Core Vesicles ◽  
Intracellular Calcium Ion ◽  
Individual Vesicle ◽  
Digitonin Permeabilization

Neurotransmitter release is a steep function of the intracellular calcium ion concentration ([Ca2+]i) at the release sites. Both the Ca2+ amplitude and the time course appear to be important for specifying neurotransmitter release. Ca2+ influx regulates the number of vesicles exocytosed as well as the amount of neurotransmitter each individual vesicle releases. In our study we stimulated mouse chromaffin cells in two different ways to alter Ca2+ presentation at the release sites. One method, digitonin permeabilization followed by exposure to Ca2+, allows for a large uniform global elevation of [Ca2+]i, whereas the second method, application of nicotine, depolarizes chromaffin cells and activates voltage-dependent Ca2+ channels, thereby producing more phasic and localized changes in [Ca2+]i. Using amperometry to monitor catecholamine release, we show that both kinds of stimuli elicit the exocytosis of similar quantities of neurotransmitter per large dense core vesicles (LDCVs) released. Even so, the release process was quite different for each stimulus; nicotine-elicited events were small and slow, whereas digitonin events were, in comparison, large and fast. In addition, the transient opening of the fusion pore, called the “foot,” was essentially absent in digitonin-stimulated cells, but was quite common in nicotine-stimulated cells. Thus even though both strong stimuli used in this study elicited the release of many vesicles it appears that the differences in the Ca2+ levels at the release sites were key determinants for the fusion and release of individual vesicles.

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