Isolation and characteristation of the main neutral protein from human submandibular saliva

Journey of cystatins from being mere thiol protease inhibitors to at heart of many pathological conditions

Cystatins are thiol proteinase inhibitors (TPI), present ubiquitously in animals, plants and micro-organisms. These are not merely inhibitors rather they are at heart of many pathological conditions ranging from diabetes to renal failure. These are essential for maintenance of protein balance of the cell; once this balance gets disturbed, it may lead to cell death. Thus, cystatins cannot be merely regarded as TPI's as these have been found to play a pivotal role in tumorigenesis and neurodegenerative diseases. Many studies have reported the variation in cystatin level in incidences of different types of cancer; highlighting an important role played by these inhibitors in cancer development and progression. Cystatin C is increasingly replacing creatinine as a biomarker of glomerular filtration rate (GFR) thereby highlighting the importance of this important inhibitor. Some recent studies have also reported the interaction pattern of various anti-cancer drugs with cystatins in a bid to find how these drugs affect this important inhibitors and whether these drugs have any side effect on cystatins. Thus, in this growing disease era it can be said that cystatins are no more just inhibitors blocking the activity of thiol proteases rather they play a pivotal role in variety of pathological conditions.

Cystatins in immune system

Cystatins comprise a large superfamily of related proteins with diverse biological activities. They were initially characterised as inhibitors of lysosomal cysteine proteases, however, in recent years some alternative functions for cystatins have been proposed. Cystatins possessing inhibitory function are members of three families, family I (stefins), family II (cystatins) and family III (kininogens). Stefin A is often linked to neoplastic changes in epithelium while another family I cystatin, stefin B is supposed to have a specific role in neuredegenerative diseases. Cystatin C, a typical type II cystatin, is expressed in a variety of human tissues and cells. On the other hand, expression of other type II cystatins is more specific. Cystatin F is an endo/lysosome targeted protease inhibitor, selectively expressed in immune cells, suggesting its role in processes related to immune response. Our recent work points on its role in regulation of dendritic cell maturation and in natural killer cells functional inactivation that may enhance tumor survival. Cystatin E/M expression is mainly restricted to the epithelia of the skin which emphasizes its prominent role in cutaneous biology. Here, we review the current knowledge on type I (stefins A and B) and type II cystatins (cystatins C, F and E/M) in pathologies, with particular emphasis on their suppressive vs. promotional function in the tumorigenesis and metastasis. We proposed that an imbalance between cathepsins and cystatins may attenuate immune cell functions and facilitate tumor cell invasion.

The effect of acquired salivary pellicle on the surface free energy and wettability of different denture base materials

OBJECTIVE

The objective of the present study was to evaluate the effect of salivary coating on the wettability and surface free energy of different denture base materials.

METHODS

Five acrylic resin and two metallic denture base materials were investigated. Ten specimens of each material (20 x 15x1.5mm) were fabricated and a standardized method was used for polishing the test specimens. Whole unstimulated saliva was collected from a single healthy donor. The wettability properties of the materials were tested before and after organic layer formation. The wetting forces were determined according to the Wilhelmy Plate Technique. Diiodomethane, ethylene glycol and formamide were used as probe liquids. The contact angles, Lifshitz-van der Waals surface energy components, Lewis acid-base surface energy components and total surface energies were calculated using the equations described in the paper. The significance of the differences in the experimentally determined surface energies of different denture materials are calculated by statistical methods.

CONCLUSIONS

Light-cured acrylic resin was the most wettable material with a significant basic character. Organic layers decreased the total surface free energies of all materials and at the same time imparted a more basic character. The coatings had a homogenizing effect in terms of the surface free energy components of the denture materials, nevertheless, their adhesive properties were still influenced by the substrate employed.

Effect of sympathectomy on isoproterenol-induced expression of the cysteine proteinase inhibitor gene, cystatin S, in rat submandibular glands

The autonomic nervous system regulates the secretory function of salivary glands. The volume, rate of secretion and composition of saliva are regulated by both sympathetic (alpha 1-, alpha 2 and beta 1-adrenergic) and parasympathetic (muscarinic and cholinergic) receptor systems. The rat cystatin S gene, a member of family 2 of the cysteine proteinase inhibitor superfamily, has a very defined pattern of expression during the postnatal development of the rat submandibular gland. Its expression is not detected in the fetus or in rats up to three weeks of age. After this time, the amount of cystatin S mRNA increases, reaching a conspicuously high concentration at 28 days, and then it declines to a barely detectable level at 32 days of age; cystatin S mRNA is not detectable in the glands of adult animals. However, the beta-adrenoreceptor agonist isoproterenol (IPR) induces high concentrations of cystatin S mRNA in the submandibular gland in vivo. This paper reports experiments analysing the participation of the sympathetic nervous system in the IPR-induced expression of the cystatin S gene. Sympathetic denervation (unilateral and bilateral) by removing the superior cervical ganglion 14 days before a single injection of IPR reduced the expression of the cystatin S gene. Chemical denervation by reserpine (a drug that depletes neurotransmitters in sympathetic nerve terminals) also reduced IPR-induced expression of the gene. Morphological analyses of sympathectomized and reserpine-treated glands showed that the structure of the gland was similar to that of glands of intact animals and to those not treated with reserpine. The hypertrophic response to IPR was less obvious in the sympathectomized glands, but was similar in reserpine treated animals. Collectively, these data suggest that even in the presence of a functional beta 1-adrenergic receptor pathway, factor(s) from the sympathetic nervous system may be required for IPR-induced expression of the cystatin S gene.

Cystatins in health and disease

Proteolytic enzymes have many physiological functions in plants, bacteria, viruses, protozoa and mammals. They play a role in processes such as food digestion, complement activation or blood coagulation. The action of proteolytic enzymes is biologically controlled by proteinase inhibitors and increasing attention is being paid to the physiological significance of these natural inhibitors in pathological processes. The reason for this growing interest is that uncontrolled proteolysis can lead to irreversible damage e.g. in chronic inflammation or tumor metastasis. This review focusses on the possible role of the cystatins, natural and specific inhibitors of the cysteine proteinases, in pathological processes.

Efficient production of biologically active human salivary cystatins in Escherichia coli

Different Escherichia coli expression systems were used for expression of cDNA clones encoding the human salivary cysteine proteinase (CysP) inhibitors, cystatins SN and S (CsnSN and CsnS). These included pOTSNco12 that expresses foreign sequences as authentic (nonfusion) proteins, and pGEX-2T that directs the synthesis of foreign polypeptides as fusion proteins with glutathione S-transferase (GST). The pOTS vector produced low levels of recombinant CsnSN (reCsnSN) that was localized in the soluble fraction, but not easily purified. The pGEX vector, on the other hand, produced much higher yields of the fusion protein, GST::CsnSN, that was localized almost entirely in the insoluble protein fraction. Solubilized and refolded GST::CsnSN inhibited the CysP, papain, more efficiently than chicken egg white Csn, indicating that the recombinant product was biologically active and that the GST carrier did not interfere with the biological activity. The pGEX-2T vector was subsequently used for the large-scale production of reCsnSN and reCsnS that were cleaved from the GST by thrombin and purified by DE-52 cellulose chromatography. ReCsnSN inhibited papain almost as efficiently as salivary CsnSN, while the reCsnS showed lower inhibitory activity as compared to both salivary CsnS and reCsnSN.

Cystatins--inhibitors of cysteine proteinases

The cystatin superfamily of proteins, derived from a common ancestor, is comprised of a diverse group of potent cysteine proteinase inhibitors and antibacterial/viral agents grouped into several families. This review concentrates on family 2 cystatins, namely, the human salivary cystatins and cystatin C. Emphasis is given to their physicochemical and functional properties at both the protein and the molecular level. The role of cystatins in disease processes, including those in the oral cavity, is also discussed. Finally, future directions for cystatin research in oral biology are presented.

Binding of corroded ions to human saliva

Employing equilibrium dialysis, the binding abilities of Cu, Al, Co and Cr ions from corroded Cu-Al and Co-Cr dental casting alloys towards human saliva and two of its gel chromatographic fractions were determined. Results indicate that both Cu and Co bind to human saliva i.e. 0.045 and 0.027 mg/mg protein, respectively. Besides possessing the largest binding ability, Cu also possessed the largest binding capacity. The saturation of Cu binding was not reached up to the limit of 0.35 mg protein/ml employed in the tests, while Co reached full saturation at about 0.2 mg protein/ml. Chromium showed absolutely no binding to human saliva while Al ions did not pass through the dialysis membranes. Compared to the binding with solutions that were synthetically made up to contain added salivary-type proteins, it is shown that the binding to human saliva is about 1 order of magnitude larger, at least for Cu ions.

The isolation of a family of cysteine-containing phosphoproteins from human submandibular-sublingual saliva

A family of acidic proteins has been isolated from human submandibular-sublingual saliva using Sephadex G-200 gel filtration, DE-52 cellulose chromatography, and immuno-affinity chromatography. These molecules were homogenous in size and by immunological criteria, but exhibited charge heterogeneity. The heterogeneity displayed was not due to gustatory stimulation or degradation during isolation procedures.

Characterization of cysteine-containing phosphoproteins from human submandibular-sublingual saliva

Members of a family of acidic proteins taken from human submandibular-sublingual saliva were designated cysteine-containing phosphoproteins, since they could be distinguished from other salivary phosphoproteins by the presence of half-cystine. These molecules consisted of a single peptide chain of approximately 14,000 daltons. Their isoelectric points ranged from 4.3 to 5.9. Two groups (C2 and C3) were O-phosphorylated. Their charge heterogeneity was apparently due to variations in content of phosphate and acidic and basic amino acids.