Cell-cell recognition: specific binding of Microciona sponge aggregation factor to homotypic cells and the role of calcium ions

Biochemistry ◽  
1980 ◽  
Vol 19 (5) ◽  
pp. 1038-1042 ◽  
Author(s):  
James E. Jumblatt ◽  
Verena Schlup ◽  
Max M. Burger
Keyword(s):  
Calcium Ions ◽  
Specific Binding ◽  
Cell Recognition ◽  
Aggregation Factor ◽  
Cell Cell

A possible model for cell-cell recognition via surface macromolecules

1975 ◽  
Vol 271 (912) ◽  
pp. 379-393 ◽  
Keyword(s):  
Cell Sheet ◽  
Alternative Possibilities ◽  
Cell Recognition ◽  
Cell Distribution ◽  
Free System ◽  
Random Movement ◽  
Recognition Process ◽  
Aggregation Factor ◽  
Species Specific ◽  
Cell Cell

Alternative possibilities for the establishment of the proper cell distribution during embryogenesis are summarized at the beginning, followed by an assessment of the examples known so far where cell-cell recognition is known to be mediated via cell surface components. In the second part the species-specific recognition process which occurs during the sorting-out of dissociated sponge cells is analysed since it may serve as a possible model for cell-cell recognition in higher animals. Three possible mechanisms for the establishment of proper cell distribution are considered. These include, first, chemotaxis; secondly, guidance of cell or cell sheet movement by extracellular matrix or by surrounding cells and thirdly, random movement followed by recognition at the final point of destination. Recognition is necessary for both of the two latter processes, i.e. for cell guidance as well as for locking the cells into their final position after random movement. Two basically different recognition mechanisms should be distinguished from each other. On the one hand cells may recognize each other with the help of macromolecules situated in or just outside of the plasmamembrane which fit to each other like enzymes and substrates or antibodies and antigens. On the other hand, cells may exchange information by exchanging cytoplasmatic components via vesicles or gap junctions. The species-specific aggregation of dissociated sponge cells is considered to be a possible model for cell-cell recognition in higher animals. A proteoglycan-like intercellular macromolecule called aggregation factor seems to mediate recognition of a given species of cells in the reaggregation process of dissociated cells. The data available at the present time suggest that a monovalent surface macromolecule (baseplate) may mediate the recognition process probably by recognizing the carbohydrate side chains of the multivalent proteoglycan aggregation factor. A cell-free system was devised to mimic this aggregation process. Addition of aggregation factor to baseplate-coated sepharose beads of approximately the size of the original sponge cells has essentially the same characteristics as the cellular system. Macromolecule-coded surface information for the recognition between cells has not been established during the embryogenesis of higher animals and remains an interesting challenge.

Lanthanides as substitutes for calcium ions in the activation of plant α-type phospholipase D

2014 ◽  
Vol 395 (7-8) ◽  
pp. 791-799 ◽  
Author(s):  
Lars Dressler ◽  
Ralph Golbik ◽  
Renate Ulbrich-Hofmann
Keyword(s):  
Rare Earth ◽  
Phospholipase D ◽  
Calcium Ions ◽  
Specific Binding ◽  
Maximum Activity ◽  
Rare Earth Ions ◽  
White Cabbage ◽  
Displacement Experiments ◽  
Triton X

Abstract Most types of phospholipase D (PLD) from plants contain a C2 domain and are activated by Ca2+ ions. In this study, other metal ions such as Mg2+, La3+, Ce3+, Tb3+ and Y3+ were examined as effectors of recombinantly produced α-type PLD from white cabbage. All the rare earth ions were able to substitute for Ca2+. The activation curves and displacement experiments reflect a 10- to 50-fold higher affinity of PLD for these ions than for Ca2+; however, the maximum activity attained only 36% of that in the presence of Ca2+. Mg2+ displaced Ca2+ without being able to activate PLD. All ions were bound to the substrate micelles consisting of phosphatidyl-p-nitrophenol, Triton X-100 and SDS (1:8:1, by mole). The affinity of rare earth ions to the micelles was 100-fold higher than that of Ca2+ and Mg2+. A conformational change of the enzyme induced by the low affinity but specific binding of Ca2+ ions is concluded to be essential for maximal PLD activity. As demonstrated by the measurement of Tb3+ fluorescence, the substitution of Ca2+ by rare earth ions provides a new avenue for studying the enigmatic role of Ca2+ ions in the modulation of PLD activity in plants.

Mitochondrial matrix calcium ions regulate energy production in myocardium: A cytochemical study

1990 ◽  
Vol 48 (2) ◽  
pp. 166-167
Author(s):  
W.A. Jacob ◽  
R. Hertsens ◽  
A. Van Bogaert ◽  
M. De Smet
Keyword(s):  
Energy Metabolism ◽  
Calcium Ions ◽  
Energy Production ◽  
Regulation Of Respiration ◽  
Free Calcium ◽  
Mitochondrial Matrix ◽  
Cytochemical Study ◽  
Nmr Techniques

In the past most studies of the control of energy metabolism focus on the role of the phosphorylation potential ATP/ADP.Pi on the regulation of respiration. Studies using NMR techniques have demonstrated that the concentrations of these compounds for oxidation phosphorylation do not change appreciably throughout the cardiac cycle and during increases in cardiac work. Hence regulation of energy production by calcium ions, present in the mitochondrial matrix, has been the object of a number of recent studies.Three exclusively intramitochondnal dehydrogenases are key enzymes for the regulation of oxidative metabolism. They are activated by calcium ions in the low micromolar range. Since, however, earlier estimates of the intramitochondnal calcium, based on equilibrium thermodynamic considerations, were in the millimolar range, a physiological correlation was not evident. The introduction of calcium-sensitive probes fura-2 and indo-1 made monitoring of free calcium during changing energy metabolism possible. These studies were performed on isolated mitochondria and extrapolation to the in vivo situation is more or less speculative.

On the Role of Transferrin in 67Ga Uptake by Tumor Cells

1988 ◽  
Vol 27 (04) ◽  
pp. 151-153
Author(s):  
P. Thouvenot ◽  
F. Brunotte ◽  
J. Robert ◽  
L. J. Anghileri
Keyword(s):  
Specific Binding ◽  
Subcellular Fractionation ◽  
Animal Blood ◽  
Tumor Bearing ◽  
Cell Structures ◽  
The Difference ◽  
Sarcoma Cells ◽  
In Vitro Uptake

In vitro uptake of 67Ga-citrate and 59Fe-citrate by DS sarcoma cells in the presence of tumor-bearing animal blood plasma showed a dramatic inhibition of both 67Ga and 59Fe uptakes: about ii/io of 67Ga and 1/5o of the 59Fe are taken up by the cells. Subcellular fractionation appears to indicate no specific binding to cell structures, and the difference of binding seems to be related to the transferrin chelation and transmembrane transport differences

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