scholarly journals Effect of Ouabain and Other Drugs on Calcium-Binding Activity of Isolated Cardiac Endoplasmic Reticulum

1972 ◽  
Vol 22 ◽  
pp. 27
Author(s):  
Setsuharu Fujita ◽  
Osamu Kamata
Keyword(s):  
Endoplasmic Reticulum ◽  
Calcium Binding ◽  
Binding Activity

Identification of a set of calcium-binding proteins in reticuloplasm, the luminal content of the endoplasmic reticulum

1988 ◽  
Vol 91 (1) ◽  
pp. 61-70 ◽  
Author(s):  
D.R. Macer ◽  
G.L. Koch
Keyword(s):  
Endoplasmic Reticulum ◽  
Calcium Binding ◽  
Binding Proteins ◽  
Binding Capacity ◽  
Equilibrium Dialysis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Calcium Ionophore ◽  
Binding Activity ◽  
Calcium Binding Proteins ◽  
Molecular Weights

A procedure was developed for the isolation of reticuloplasm, the luminal material of the endoplasmic reticulum (ER). A reticuloplasm-rich extract was prepared from a murine plasmacytoma cell line that contains large amounts of ER, by first extracting the cytoplasmic contents using hypotonic lysis to yield ER-rich ‘shells’ followed by mechanical lysis to release the ER contents. The extract contains five major proteins with apparent molecular weights of 100, 75, 60, 58 and 55 (X 10(3] Mr by SDS-polyacrylamide gel electrophoresis. The 100, 75 and 58 (X 10(3] Mr species were identified as the known ER proteins endoplasmin, BiP and PD1, respectively. The ER association of the 60 and 55 (X 10(3] Mr proteins was confirmed by confocal fluorescence microscopy with affinity-purified antibodies. Equilibrium dialysis with isolated reticuloplasm gave a calcium-binding capacity of 300 nmoles calcium per mg protein with half-maximal binding at 3 mM-Ca2+. Purified endoplasmin bound 280 nmoles calcium per mg protein at a calcium concentration of 5 mM-Ca2+. A calcium overlay test revealed that, in addition to endoplasmin, reticuloplasm contained at least three other calcium-binding proteins: i.e. BiP, PDI and the 55 X 10(3) Mr protein, respectively, with endoplasmin and the 55 X 10(3) Mr protein (CRP55) accounting for the major proportion of the calcium-binding activity. Treatment of cells with calcium ionophore led to the specific over-expression of the major calcium-binding reticuloplasmins endoplasmin, BiP and CRP55. These studies show that the lumen of the ER contains a family of proteins with the capacity to bind significant amounts of calcium in the millimolar range and thereby to confer upon the ER the ability to perform a calcium storage function analogous to that of the sarcoplasmic reticulum in muscle cells.

scholarly journals Nonstructural 5A Protein of Hepatitis C Virus Regulates Soluble Resistance-Related Calcium-Binding Protein Activity for Viral Propagation

2015 ◽  
Vol 90 (6) ◽  
pp. 2794-2805 ◽  
Author(s):  
Giao V. Q. Tran ◽  
Trang T. D. Luong ◽  
Eun-Mee Park ◽  
Jong-Wook Kim ◽  
Jae-Woong Choi ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Protein Interaction ◽  
Calcium Binding ◽  
Crucial Role ◽  
Binding Protein ◽  
Binding Activity ◽  
Calcium Binding Protein ◽  
Virus Propagation ◽  
Ns5a Protein

ABSTRACTHepatitis C virus (HCV) is a major cause of chronic liver disease and is highly dependent on cellular proteins for virus propagation. To identify the cellular factors involved in HCV propagation, we recently performed protein microarray assays using the HCV nonstructural 5A (NS5A) protein as a probe. Of 90 cellular protein candidates, we selected the soluble resistance-related calcium-binding protein (sorcin) for further characterization. Sorcin is a calcium-binding protein and is highly expressed in certain cancer cells. We verified that NS5A interacted with sorcin through domain I of NS5A, and phosphorylation of the threonine residue 155 of sorcin played a crucial role in protein interaction. Small interfering RNA (siRNA)-mediated knockdown of sorcin impaired HCV propagation. Silencing of sorcin expression resulted in a decrease of HCV assembly without affecting HCV RNA and protein levels. We further demonstrated that polo-like kinase 1 (PLK1)-mediated phosphorylation of sorcin was increased by NS5A. We showed that both phosphorylation and calcium-binding activity of sorcin were required for HCV propagation. These data indicate that HCV modulates sorcin activity via NS5A protein for its own propagation.IMPORTANCESorcin is a calcium-binding protein and regulates intracellular calcium homeostasis. HCV NS5A interacts with sorcin, and phosphorylation of sorcin is required for protein interaction. Gene silencing of sorcin impaired HCV propagation at the assembly step of the HCV life cycle. Sorcin is phosphorylated by PLK1 via protein interaction. We showed that sorcin interacted with both NS5A and PLK1, and PLK1-mediated phosphorylation of sorcin was increased by NS5A. Moreover, calcium-binding activity of sorcin played a crucial role in HCV propagation. These data provide evidence that HCV regulates host calcium metabolism for virus propagation, and thus manipulation of sorcin activity may represent a novel therapeutic target for HCV.

scholarly journals The Heparin-Binding Activity of Secreted Modular Calcium-Binding Protein 1 (SMOC-1) Modulates Its Cell Adhesion Properties

PLoS ONE ◽  
2013 ◽  
Vol 8 (2) ◽  
pp. e56839 ◽  
Author(s):  
Marina Klemenčič ◽  
Marko Novinec ◽  
Silke Maier ◽  
Ursula Hartmann ◽  
Brigita Lenarčič
Keyword(s):  
Cell Adhesion ◽  
Calcium Binding ◽  
Binding Protein ◽  
Binding Activity ◽  
Calcium Binding Protein ◽  
Heparin Binding ◽  
Adhesion Properties

scholarly journals Involvement of the stress protein HSP47 in procollagen processing in the endoplasmic reticulum

1992 ◽  
Vol 117 (4) ◽  
pp. 903-914 ◽  
Author(s):  
A Nakai ◽  
M Satoh ◽  
K Hirayoshi ◽  
K Nagata
Keyword(s):  
Endoplasmic Reticulum ◽  
Stress Protein ◽  
Normal Growth ◽  
Growth Conditions ◽  
Binding Activity ◽  
Pulse Label ◽  
Intact Cells ◽  
Collagen Binding ◽  
Chase Period ◽  
Helix Formation

The 47,000-D collagen-binding glycoprotein, heat shock protein 47 (HSP47), is a stress-inducible protein localized in the ER of collagen-secreting cells. The location and collagen-binding activity of this protein led to speculation that HSP47 might participate in collagen processing. Chemical crosslinking studies were used to test this hypothesis both before and after the perturbation of procollagen processing. The association of procollagen with HSP47 was demonstrated using cleavable bifunctional crosslinking reagents. HSP47 and procollagen were shown to be coprecipitated by the treatment of intact cells with anti-HSP47 or with anticollagen antibodies. Furthermore, several proteins residing in the ER were noted to be crosslinked to and coprecipitated with HSP47, suggesting that these ER-resident proteins may form a large complex in the ER. When cells were heat shocked, or when stable triple-helix formation was inhibited by treatment with alpha,alpha'-dipyridyl, coprecipitation of procollagen with HSP47 was increased. This increase was due to the inhibition of procollagen secretion and to the accumulation of procollagen in the ER. Pulse label and chase experiments revealed that coprecipitated procollagen was detectable as long as procollagen was present in the endoplasmic reticulum of alpha,alpha'-dipyridyl-treated cells. Under normal growth conditions, coprecipitated procollagen was observed to decrease after a chase period of 10-15 min, whereas total procollagen decreased only after 20-25 min. In addition, the intracellular association between HSP47 and procollagen was shown to be disrupted by a change in physiological pH, suggesting that the dissociation of procollagen from HSP47 is pH dependent. These findings support a specific role for HSP47 in the intracellular processing of procollagen, and provide evidence of a new category of "molecular chaperones" in terms of its substrate specificity and the dissociation mechanism.

Radioimmunoassay Studies of Intestinal Calcium-binding Protein in the Pig. II. The Distribution of Intestinal CaBP in Pig Tissues

1975 ◽  
Vol 53 (6) ◽  
pp. 1135-1140 ◽  
Author(s):  
B. M. Arnold ◽  
M. Kuttner ◽  
D. M. Willis ◽  
A. J. W. Hitchman ◽  
J. E. Harrison ◽  
...  
Keyword(s):  
Small Intestine ◽  
Calcium Binding ◽  
Binding Protein ◽  
Gel Filtration ◽  
Protein S ◽  
Binding Activity ◽  
Calcium Binding Protein ◽  
Distal Small Intestine ◽  
Specific Radioimmunoassay ◽  
Kidney Liver

Using a specific radioimmunoassay for porcine intestinal calcium-binding protein (CaBP), we have measured the concentration of CaBP in the various tissues and organs of normal pigs. Intestinal CaBP was present in highest concentration in the upper small intestine, with lower concentrations in the distal small intestine. Intestinal CaBP was also found, in lower concentrations, in kidney, liver, thyroid, pancreas, and blood. In all other tissues, including parathyroid, bone, skeletal muscle, and brain, CaBP immunoreactivity was undetectable or less than in blood. The elution profile of calcium-binding activity and immunoreactivity from gel filtration analysis of kidney and parathyroid extracts suggest that the calcium-binding protein in the parathyroid gland, and the major calcium-binding protein(s) in the kidney, are chemically and immunochemically different from intestinal CaBP.

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