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

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.

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Design of a Calcium-Binding Protein with Desired Structure in a Cell Adhesion Molecule

Journal of the American Chemical Society ◽

10.1021/ja0431307 ◽

2005 ◽

Vol 127 (7) ◽

pp. 2085-2093 ◽

Cited By ~ 44

Author(s):

Wei Yang ◽

Anna L. Wilkins ◽

Yiming Ye ◽

Zhi-ren Liu ◽

Shun-yi Li ◽

...

Keyword(s):

Cell Adhesion ◽

Adhesion Molecule ◽

Calcium Binding ◽

Cell Adhesion Molecule ◽

Binding Protein ◽

Calcium Binding Protein ◽

A Cell

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

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y75-158 ◽

1975 ◽

Vol 53 (6) ◽

pp. 1135-1140 ◽

Cited By ~ 27

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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Calcium-ion-binding activity in human small-intestinal mucosal cytosol Purification of two proteins and interrelationship of calcium-binding fractions

Biochemical Journal ◽

10.1042/bj1970055 ◽

1981 ◽

Vol 197 (1) ◽

pp. 55-65 ◽

Cited By ~ 8

Author(s):

M Davie

Keyword(s):

Molecular Weight ◽

Calcium Binding ◽

Binding Proteins ◽

Binding Protein ◽

Mammalian Species ◽

Binding Activity ◽

Calcium Binding Proteins ◽

Calcium Binding Protein ◽

Small Intestinal Mucosa ◽

Small Intestinal

Ca2+-binding activity was investigated in human small-intestinal mucosal cytosol. Binding was detected in fractions with molecular weights of 28000 and about 900000, as determined by gel filtration. No binding was found at molecular weight 12000-13000 (the molecular weight of calcium-binding protein in lower mammalian species) until the cytosol had been subjected to a hollow-fibre-filtration step. The appearance of Ca2+-binding at molecular weight 12000-13000 was associated with a decline in the 28000-mol.wt. calcium-binding fraction. The 12000-13000-mol.wt. fraction contained two distinct calcium-binding proteins. One of these proteins had properties similar to those of pig calcium-binding protein. Antiserum to this protein reacted against the 28000-mol.wt calcium-binding fraction in cytosol from human small-intestinal mucosa and from human kidney. An immunoassay method for one of the calcium-binding proteins was established. In normal duodenal mucosa the concentration was 915 micrograms/g and in the ileum it was 443 micrograms/g of mucosa. A subject with hypercalcaemic sarcoidosis had 1200 micrograms/g of mucosa in the jejunum, and a subject with an undetectable concentration of plasma 25-hydroxycholecalciferol had concentrations of calcium-binding protein in the mucosa similar to those found in normal subjects.

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