Changes in submaxillary gland gene expression in F344 rats by multiple dosing of theophylline

Multiple exposure to theophylline, a phosphodiesterase (PDE) inhibitor, induces acinar hypertrophy in the salivary gland. This study examined the effect of theophylline on the gene expression of secretory proteins and phosphodiesterases in the submaxillary gland. Male F344 rats received saline or theophylline (50 mg/kg) intraperitoneally for 4 days. The gene expressions for the secretory protein, cystatin S (CysS), and PDE subfamilies 3A and 4D in the submaxillary gland were quantified using RT-PCR. Theophylline exposure resulted in a sustained increase in mRNA expression for CysS and PDE3A, but PDE4D gene expression was unchanged. Our results suggest that submaxillary hypertrophy is primarily caused by the enhanced transcription of CysS, and that the transcription of each PDE subfamily gene is regulated differently.

Extracellular production of human cystatin S and cystatin SA by Bacillus subtilis

We herein describe the development of a Bacillus subtilis system that can be used to produce large quantities of recombinant (r-) human salivary cystatins, a cysteine protease inhibitor of family 2 in the cystatin superfamily. The B. subtilis that lacked the alkaline protease E gene (DeltaaprE type mutant strain) was prepared by homologous recombination. The cDNA fragments coding for mature cystatins (S and SA) were ligated in frame to the DNA segment for the signal peptide of endoglucanase in the pHSP-US plasmid vector that was then use to transform the DeltaaprE type mutant strain of B. subtilis. The transformants carrying the expression vectors were cultivated in 5-L jar fermenters for 3 days at 30 degrees C. Both r-cystatin S and r-cystatin SA were successfully expressed and secreted into the culture broth, and were purified using a fast performance liquid chromatography system. The first use of DeltaaprE type mutant strain of B. subtilis made it possible to obtain a high yield of secreted protein, which makes this system an improvement over expression in Escherichia coli. We conclude that this system has high utility for expression of commercial quantities of secreted proteins.

Two-dimensional electrophoresis study of in vitro pellicle formation and dental caries susceptibility

In the present study, a proteomic approach was applied to evaluate the influence of salivary protein composition on in vitro dental pellicle formation and its possible correlation with dental caries. Whole saliva, collected from caries-free and caries-susceptible subjects, was analyzed by two-dimensional electrophoresis, and protein spots were identified by mass spectrometry. Data analysis of salivary protein composition showed a statistically significant correlation between the quantity of acidic proline-rich proteins (PRPs), lipocalin, cystatin SN and cystatin S, and samples from the caries-free group of subjects [decayed, missing or filled teeth (DMFT) = 0]. Samples from subjects with a high DMFT index appear to be correlated with high levels of amylase, immunoglobulin A, and lactoferrin. In vitro pellicle-composition experiments showed the same correlations found for whole saliva. As cystatins are known physiological inhibitors of cathepsins, the higher quantities of lipocalin, and cystatins S and SN found in the samples from the caries-free subjects suggest that inhibition of proteolytic events on other salivary proteins may indirectly provide tooth protection. The correlation between higher levels of the phosphorylated acidic PRPs 1/2 with samples from the caries-free group also suggests a protective role for these proteins.

Murine monoclonal antibody which can distinguish cystatins SA1 and SA2

To develop a diagnostic trial enabling the selective examination for a target cystatin in human body fluids, we attempted to prepare monoclonal antibodies against human cystatin SA1 (originally cystatin SA) and its variant form (cystatin SA2). BALB/c mice were immunized with recombinant (r-) cystatins SA1 and SA2. Two monoclonal antibodies designated Cys3F11 and Cys2E5 were selected. By ELISA analyses, the Cys2E5 was shown to react with r-cystatin SA2 but also somewhat with r-cystatin SA1 (22% cross-reactivity) and with plasma cystatin C (18% cross-reactivity), indicating a high specificity for cystatin SA2. The Cys3F11 reacted not only with r-cystatin SA1 but also with r-cystatin SA2 (89% cross-reactivity) and plasma cystatin C (47% cross-reactivity). This finding was further emphasized by immunoblotting of human submandibular-sublingual saliva samples. ELISA additivity test suggests that the two monoclonal antibodies bind to distinct epitopes. In conclusion, we have succeeded in producing two antibodies that discriminate the structural differences between salivary cystatins S and SN, which share more than 90% identity in amino acid sequence with cystatin SA.

Apport de l’analyse protéomique associant électrophorèse bi-dimensionnelle et spectrométrie de masse en lacrymologie

PURPOSE

Identification of a lacrimal protein by proteomic analysis, i.e., two-dimensional electrophoresis and mass spectrometry.

MATERIAL AND METHODS

We studied the tears of a 25-year-old female with adrenal gland hyperplasia and hyperandrogenism complaining of chronic dryness and mild bilateral papillary hypertrophy. An allergologic workup was negative. Agarose electrophoresis of the tears showed a bilateral high level of rapid migrated proteins.

RESULTS

Dodecyl sulfate polyacrylamide gel electrophoresis of the tears from both eyes showed a highly stained 15-kDa band after Coomassie colloidal blue coloration compared to controls. On two-dimensional electrophoresis, this band focused on a single spot at pI 7.0. After tryptic digestion in gel, peptide mass fingerprint analysis by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry provided clear identification of cystatin SN. It is known that mRNA regulated by androgens and encoding glycoproteins homologous to human cystatin exists in the rat lacrimal gland.

CONCLUSION

We conclude that the hyperandrogenism of the patient may be cause for the hypersecretion of this cystatin SN, giving an explanation for the high level of rapid migrated proteins (lipocalins). This result provides a concrete example of the proteomic tool used to identify lacrimal proteins, still largely unknown.

Cystatin SA, a cysteine proteinase inhibitor, induces interferon-γ expression in CD4-positive T cells

Recently, it has been demonstrated that family 2 cystatins upregulate interleukin-6 production by human gingival fibroblasts. In the present study, we investigated the effects of cystatin SA on cytokine production by helper T cells. Human CD4-positive T cells were cultured with phytohemagglutinin in the presence or absence of 0.1 microM recombinant cystatin SA1 or SA2. When the amounts of interleukin-4 (IL-4) and interferon-gamma (IFNgamma) were analyzed in an ELISA system after stimulation with either cystatin, no significantly increased levels of IL-4 were detected. However, the amounts of IFNgamma were significantly increased after stimulation with the cystatins. Our results suggest that salivary family 2 cystatins are involved in immune responses through the cytokine network.

Degradation of antimicrobial histatin-variant peptides in Staphylococcus aureus and Streptococcus mutans

Histidine-free variants of salivary histatin 5 have a broad antimicrobial activity against various bacteria. In relation to a possible therapeutic application, we were interested in the susceptibility of these small peptides (14 amino acids long) to microbial proteinases and whether this affects their antimicrobial activity. Analyses by SDS-PAGE of supernatants of peptide-bacteria incubation showed a reduction in protein bands within 15 minutes' incubation, as a result of cellular internalization. Degradation products of dhvar1 and dhvar2 appeared within one hour in the supernatants of Streptococcus mutans and Staphylococcus aureus. In contrast, the variants dhvar3 and dhvar4 were more resistant to degradation under the same conditions. MALDI-TOF analyses identified cleavage of dhvar1 and dhvar2 at Glu(6). The N-terminal peptide part (1-6) of dhvar1 and 2 showed no bactericidal activity, while peptide fragment (7-14) showed a highly reduced bactericidal activity.

Salivary (SD-type) cystatins: over one billion years in the making--but to what purpose?

Human saliva contains relatively abundant proteins that are related ancestrally in sequence to the cystatin superfamily. Most, although not all, members of this superfamily are potent inhibitors of cysteine peptidases. Four related genes have been identified, CST1, 2, 4 and 5, encoding cystatins SN, SA, S, and D, respectively. CST1, 4, and probably CST5 are now known to be expressed in a limited number of other tissues in the body, primarily in exocrine epithelia, and the term SD-type cystatin is more appropriate than 'salivary cystatin'. These genes are co-ordinately regulated in the submandibular gland during post-natal development. The organization of these tissue-specifically-expressed genes in the genome, and their phylogeny, indicate that they evolved from an ancestral housekeeping gene encoding the ubiquitously expressed cystatin C, and are members of a larger protein family. Their relationship to rat cystatin S, a developmentally regulated rodent submandibular gland protein, remains to be established. In this review, the evolution of the SD-type cystatins in the cystatin superfamily, their genomics, expression, and structure-function relationships are examined and compared with known cystatin functions, with the goal of providing clues to their biological roles.

Innate secretory immunity in response to laboratory stressors that evoke distinct patterns of cardiac autonomic activity

OBJECTIVE

Most infections begin at mucosal surfaces. These surfaces are covered by the secretory proteins of the exocrine glands (eg, the salivary, respiratory, and gastrointestinal glands), which provide a first line of innate defense. The release of these secretory proteins is under neuroendocrine control and thus, in theory, sensitive to modulation by psychosocial stress. This was empirically tested by measuring the salivary secretion of cystatin S, lactoferrin, alpha-amylase, the mucins MUC5B and MUC7, and total salivary protein in response to stressors known to evoke distinct patterns of cardiac autonomic activity.

METHODS

Thirty-two undergraduate volunteers were each subjected to two laboratory stressors and a control condition. Stressors were an active coping memory test and a passive coping video presentation showing surgical procedures. In the control condition participants viewed a didactic video presentation.

RESULTS

The stressors evoked the expected distinct patterns of cardiac autonomic activity. The memory test produced a strong increase in sympathetic activity (evidenced by a shortened preejection period), and a decrease in cardiac parasympathetic activity (evidenced by a decrease in heart rate variability). This active coping response was associated with an enhanced secretion ( microg/min, controlling for salivary flow rate) of MUC7, lactoferrin, alpha-amylase, and total salivary protein. Conversely, the surgical video produced an increase in cardiac vagal tone and a modest increase in sympathetic activity. This passive coping response was associated with an enhanced secretion of all proteins studied. These secretory responses were generally larger than the secretory responses during the active coping memory test. Correlation analyses indicated that for both stressors autonomic and cardiovascular reactivity was positively associated with an enhanced and prolonged secretory activity.

CONCLUSIONS

Stress-induced modulation of innate secretory immunity may be a contributing factor in the observed relationship between stress and susceptibility to infectious diseases. We further propose a more differentiated approach to acute stress by distinguishing among stressors with distinct autonomic nervous system effects.

Salivary cystatins induce interleukin-6 expression via cell surface molecules in human gingival fibroblasts

Recently, family 2 cystatins have been demonstrated to upregulate interleukin-6 (IL-6) production by human gingival fibroblasts [Biol. Chem. 381 (2000) 1143]. To elucidate the mechanism of the IL-6 inducing activity of cystatins, we tested NF-kappa B activation with salivary cystatins SA1 and SA2-stimulated human gingival fibroblast whole cell lysates. The IL-6 production by human fibroblasts in response to these cystatins was inhibited by tyrosine kinase inhibitors and an inhibitor of NF-kappa B activation. The IL-6 inducing activity of the cystatins was depressed by the anti-CD58 monoclonal antibody. These findings supply evidence that cystatins SA1 and SA2 adhere to human fibroblasts and that the event results in tyrosine phosphorylation and upregulation of the release of IL-6 mediated enhancement of NF-kappa B activity.

Sympathetic and parasympathetic regulation of cystatin S gene expression

The autonomic nervous system plays a regulatory role in the differentiation and growth of salivary glands, and in the expression of salivary specific genes. Cystatin S, a member of the evolutionarily conserved family 2 of the cysteine proteinase inhibitor superfamily, expressed in submandibular and parotid glands of rats during development, can be induced in adults by the beta-adrenergic agonist isopreterenol (IPR). It was shown previously that unilateral sympathectomy or bilateral parasympathectomy reduces IPR-induced cystatin S expression. The present experiments demonstrate that IPR-induced cystatin S gene expression in submandibular glands is reduced as early as 3 days post bilateral denervation of both branches of the autonomic nervous system. The reduction is nearly equal to that of either sympathectomy or parasympathectomy alone, suggesting that factor(s) in both sympathetic and parasympathetic fibers are simultaneously required for IPR-induced cystatin S gene expression.

Effect of sympathetic innervation on isoproterenol-induced cystatin S gene expression in rat submandibular glands during early development

The rat submandibular gland is innervated by both sympathetic and parasympathetic branches of the autonomic nervous system which, in turn, regulate the secretory function of the gland. Parasympathetic innervation of rat submandibular glands is present at birth; in contrast, sympathetic innervation reaches the glands by postnatal day 5. Isoproterenol (IPR), a beta-adrenoreceptor agonist, induces hypertrophic and hyperplastic enlargement of rat salivary glands, and induces the expression of a number of genes, including cystatin S (Cys S), a member of family 2 of the cysteine proteinase inhibitor superfamily. Cys S gene expression is tissue specific, cell type specific, occurs temporally during normal development and is not observed in adult animals unless stimulated by IPR. In addition, sympathectomy of adult rat submandibular glands reduced IPR-induced expression of the Cys S gene. This paper reports experiments analyzing the participation of the sympathetic branch of the autonomic nervous system in IPR-induced expression of the cystatin S gene during early development of the submandibular gland. The rat Cys S gene could be induced by IPR by day 3, and the level of Cys S mRNA remained constant until 8 days at which time a dramatic IPR induction of Cys S mRNA was observed. This statistically significant increase in Cys S mRNA at 8 days was diminished, but not completely suppressed, upon sympathectomy of 1-day-old animals. These data indicate that an intact sympathetic innervation is not a requisite for IPR-induced Cys S gene expression in developing submandibular glands; however, sympathetic innervation is required for the full IPR response of the Cys S gene in developing submandibular glands. The developmental experiments presented in this paper indicate that factor(s) coming from the sympathetic nervous system participate in IPR-induced expression of the Cys S gene in rat submandibular glands.

Autonomic regulation of cystatin S gene expression in rat submandibular glands

Innervation of rat submandibular and parotid glands by the autonomic nervous system regulates saliva volume, its rate of secretion and its composition. The autonomic nervous system also plays a regulatory role in the differentiation and growth of salivary glands, and in the expression of specific sets of genes. Rat cystatin S, a member of family 2 of the cysteine proteinase inhibitor superfamily, is expressed in submandibular and parotid glands of human and rat. In the rat, cystatin S gene expression is tissue- and cell type-specific, is temporally regulated during postnatal development, and not observed in adult animals. The beta-adrenergic agonist isoproterenol (IPR) induces hypertrophic and hyperplastic enlargements of rat salivary glands and the expression of a number of genes including cystatin S. Sympathectomy reduces, but does not completely block, IPR-induced expression of the cystatin S gene in submandibular glands of adult female rats, indicating the participation of sympathetic factor(s) in its regulation. Bilateral parasympathectomy also reduces IPR-induced cystatin S gene expression, suggesting a role of the parasympathetic nervous system in its regulation. Experiments described in this paper suggest that similar factor(s) arising from both the sympathetic and parasympathetic branches of the autonomic nervous system simultaneously participate in IPR-induced cystatin S gene expression in submandibular glands.

Differential effect toward inhibition of papain and cathepsin C by recombinant human salivary cystatin SN and its variants produced by a baculovirus system

Human salivary cystatin SN (CsnSN) is a member of the cystatin superfamily of cysteine proteinase inhibitors. In this study we used a baculovirus expression system to produce a full-length unaltered CsnSN and its variants. The variants were constructed with the changes in the three predicted proteinase-binding regions: the N-terminus (variant N(12-13), G12A-G13A), beta-hairpin loop I (variant L(56-58), Q56G-T57G-V58G) and beta-hairpin loop II (variant L(106-107), P106G-W107G). The secreted CsnSNs were purified using sequential spiral cartridge ultrafiltration and DE-52 radial flow chromatography. The purified proteins were examined for papain- and cathepsin C-inhibition. The wild-type CsnSN, and variants N(12-13) and L(106-107) bound tightly to papain (K(i) < 10 pM), whereas mutation in the loop I reduced binding affinity 5700-fold (K(i) = 57 nM). On the other hand, the wild-type CsnSN bound to cathepsin C less tightly (K(i) = 100 nM). The mutation in the N-terminus or loop I reduced binding affinity by 16 (K(i) = 1.6 microM)- and 19-fold (K(i) = 1.9 microM), respectively, while mutation in loop II resulted in an ineffective cathepsin C inhibitor (K(i) = 14 microM). Collectively, these results suggest that the N-terminal G12-G13 residues of CsnSN are not essential for papain inhibition but play a role in cathepsin C inhibition; residues Q56-T57-V58 in the loop I are essential for both papain and cathepsin C inhibitions, and residues P106-W107 in the loop II are not important for papain inhibition but essential for cathepsin C inhibition. These results demonstrated that CsnSN variants have different effects toward different cysteine proteinases.

Purification of large quantities of human salivary cystatins S, SA and SN: their interactions with the model cysteine protease papain in a non-inhibitory mode

OBJECTIVES

Our aim was to purify large quantities of human salivary cystatins S, SA and SN in order to determine whether these salivary cystatins have a stable interaction with cysteine proteases at a second binding site, other than the protease active site. This property may affect their availability to act as cysteine protease inhibitors within the oral environment.

METHODS

Salivary cystatins S, SA and SN were purified from human submandibular sublingual saliva to homo- geneity by column chromatography. Formation of stable complexes between the model cysteine protease papain in the absence of reductant was assessed by SDS-PAGE and probing Western blots with antibody to human salivary cystatin SN. Proteolytic activity of the complex was determined in the gel after electrophoresis.

RESULTS AND CONCLUSIONS

Only cystatin SN (14.3 kD) was found to form a stable complex with papain (22 kD) that could be separated by SDS-PAGE producing a Coomassie stained band at (37 kD). After western transfer this same band (37 kD) cross-reacted with antibody to SN. In the presence of E64, an active site inhibitor of cysteine proteases, the same complex was formed, suggesting that SN is able to bind to papain at a site other than the active site. Activity staining of the gel confirmed that this complex (-E64) retained proteolytic activity. Such complex formation between cystatin SN and cysteine proteases in a non-inhibitory mode may reduce its availability to act as an effective cysteine protease inhibitor in the oral environment.

Capsaicin induces cystatin S-like substances in submandibular saliva of the rat

Irritating dietary substances such as tannin and papain have been reported to alter the morphology of salivary glands and their secretions. Such alterations can be one line of protection from toxic or irritating substances in food. We investigated the effects of dietary capsaicin (a pungent ingredient of hot red pepper) on the rat submandibular gland and its secretions. Several groups of animals were offered either control diets or diets containing capsaicin (from 0.0001 to 0.1%) for seven days. Higher concentrations suppressed food consumption for two days, after which only the highest concentration continued to reduce intake. The relative weight of the salivary glands in capsaicin-diet groups increased in a dose-dependent fashion, and new proteins appeared in the submandibular saliva. Chromatographic and electrophoretic properties of these proteins were identical or similar to those of isoproterenol-induced proteins. After affinity chromatography of the new protein fraction on a Cm-papain Sepharose 4B column, SDS-electrophoresis of the eluate revealed three major bands (15,500, 16,500, and 28,000 kDa). Hydrolysis of N-benzoyl-D,L-arginine-p-nitroanilide by papain (a cysteine protease) decreased in the presence of the new protein fraction, suggesting that these proteins have cystatin-like activity (inhibition of cysteine protease). Denervation of the glossopharyngeal nerve suppressed induction of these proteins. The results suggest that dietary capsaicin induces cystatin S-like substances in submandibular saliva by stimulating the reflex arc involving the glossopharyngeal nerve. These proteins likely facilitate ingestion of diets containing the irritating substance.

The 5'-flanking sequence and regulatory elements of the cystatin S gene

The gene encoding rat cystatin S (Cys S), a salivary gland-specific secretory protein, has CAAT and TATA boxes upstream of the inititation codon (Cox and Shaw, 1992), and contains regions that resemble those of other hormonally responsive eukaryotic genes. The 5'-flanking sequence of the rat Cys S gene has a potential CREB/AP-1 binding site (Rupp et al., 1990; Trejo et al., 1992), two potential glucocorticoid responsive elements (GREs, Drouin et al., 1989), and a possible GR/PR (glucocorticoid/progesterone) responsive element (Forman and Samuels, 1990). One of these potential GREs is adjacent to a potential AP-2 binding site, and another is typical of the glucocorticoid and progesterone receptor binding site. In this report, we have identified three regions in the 5'-flanking region of the Cys S gene that are found in salivary gland-specific genes (Ting et al., 1992) with a GT-rich region located between conserved elements II and III. Transfection experiments described in this paper suggest that a 281-bp DNA fragment from the Cys S gene promoter region with conserved elements II and III, the GT-rich region, and a possible GR/PR responsive element contains a negative regulatory element. In addition, our experiments suggest that the GT-rich region by itself is acting as a positive regulatory element.

Structure/function analysis of human cystatin SN and comparison of the cysteine proteinase inhibitory profiles of human cystatins C and SN

Cystatins are reversible, competitive inhibitors of cysteine proteinases. Their inhibitory profiles, as well as their affinities for target enzymes, vary with different cysteine proteinases. Human cystatin C and salivary cystatin SN are 120- and 121-amino-acid (a.a.) proteins, respectively, and both contain 2 disulfide bonds. In this study, we examined the structure/function relationship of cystatin SN with respect to the inhibition of papain, with particular emphasis on the role of cystatin SN's cysteine residues, and addressed the inhibitory profiles of these two human cystatins on several cysteine proteinases (papain, clostripain, and calpain II). The full-length recombinant cystatin C and cystatin SN, and cystatin SN variants (C-truncated [C-tr; a.a. 1-102], delta 56-60 deletion, cysteine 74-->serine [C74S], cys 84-->serine [C84S], cysteine 98-->serine [C98S], and cysteine 118-->serine [C118S]) were cloned, expressed, and produced in the pET30(b) and pGEX2T Escherichia coli expression systems. All recombinant proteins were tested for the inhibition of papain, and the full-length proteins were also tested for the inhibition of clostripain and calpain II. The secondary structures of the cystatins were also determined and compared. The results showed that the full-length cystatin C and cystatin SN, and the cystatin SN variants C98S and C118S inhibited the activity of papain. However, cystatin SN C-tr and delta 56-60 variants exhibited no inhibitory activity toward papain, while the cystatin SN variants C74S and C84S exhibited slight inhibition at higher concentrations. These results suggested that in the inhibition of papain by cystatin SN, the first disulfide loop is more important than the second. In addition, cystatin C, but not cystatin SN, inhibited calpain II, while neither cystatin inhibited clostripain, and these results, in conjunction with those from other studies, indicated that cystatin C is a broader-spectrum inhibitor of cysteine proteinases than cystatin SN.

Functional aspects of the human salivary cystatins in the oral environment

OBJECTIVES

The aim of this study was to investigate the cysteine protease inhibitory properties of the human salivary cystatins S, SA and SN in order to identify potential in vivo target cysteine proteases which may include those involved in periodontal tissue destruction. In addition, the potential role of the salivary cystatins with respect to the tooth mineral balance and pellicle formation was also investigated.

METHODS

Salivary cystatins S major, S minor, SA, SAT (a truncated form of SA) and SN were purified from human submandibular sublingual saliva. Sensitive fluorometric assays were used to test the inhibitory action of each purified form of salivary cystatin against a variety of cysteine proteases and to determine whether pH affected their inhibitory activity towards the well-characterized cysteine protease papain. Their potential role in the mineral balance of the tooth was assessed by the measurement of calcium binding and the rate of binding to carbonated apatite (CAP).

RESULTS AND CONCLUSIONS

Salivary cystatin SN was found to inhibit the human lysosomal cathepsins B, H and L and salivary cystatin SA was found to inhibit human lysosomal cathepsin L in vitro. These proteases are involved in periodontal tissue destruction and these data suggest that salivary cystatins SA and SN are involved in the control of the proteolytic events in vivo. Salivary cystatin S was not an inhibitor of the cysteine proteases tested suggesting that its primary role is not as a cysteine protease inhibitor. However, S was able to bind more calcium and bind more rapidly to CAP than SA or SN, suggesting that its primary role in the oral environment is likely to be the involvement with the mineral balance of the tooth.

Sequence variations of the CST2 gene related to the polymorphism of salivary cystatin SA

The CST2 locus has two polymorphic alleles, CST2*1 and CST2*2, which produce cystatin proteins SAI and SA2, respectively (Shintani et al., 1994). The purpose of this study was to define nucleotide sequence variations of the protein-coding region of the two alleles. The variations were investigated by direct sequencing of amplified DNA from individuals with different CST2 phenotypes. The sequence of three exons obtained from DNA of the CST2 1 phenotype was found to be identical to the published sequence of the CST2 gene (Saitoh et al., 1987), whereas two-point mutations were found in the sequence obtained from DNA of the CST2 2 phenotype. One of the mutations was a G --> A transition in exon 2, resulting in loss of a commonly occurring AciI restriction site. This mutation resulted in a Gly59 --> Asp59 substitution in the protein. The other mutation was an A --> T transversion in exon 3, resulting in the generation of a SfaNI restriction site. This mutation also produced a Glu120 --> Asp120 substitution in the protein. PCR-RFLP assay with AciI and SfaNI restriction enzymes revealed that the two-point mutations were always correlated with cystatin SA polymorphism. The difference in the electrophoretic positions of the two proteins, SA1 and SA2, in a basic gel and in an isoelectric focusing gel agreed with the expected mobilities of the proteins with the SA2 variant at a more anodal position. The CST2*2 allele is a unique allele, which shows amino acid substitution in one of the most conserved regions responsible for cysteine proteinase inhibitory activity.

Postnatal changes of gene expression for tissue inhibitors of metalloproteinase-1 and -2 and cystatins S and C, in rat submandibular gland demonstrated by quantitative reverse transcription-polymerase chain reaction

The rat submandibular gland is not fully developed at birth and definitive differentiation takes place postnatally. The steady-state mRNA expression for the four proteinase inhibitor molecules, tissue inhibitors of metalloproteinase (TIMP)-1 and -2, and cystatins S and C, and for a housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase (G3PDH), in rat submandibular glands was measured by quantitative competitive reverse transcription-polymerase chain reaction (RT-PCR) at different stages of postnatal development. The gene-expression patterns of TIMP-1 and -2 relative to G3PDH were similar to each other. The TIMP-2 and cystatin C genes were more highly expressed than those of TIMP-1 and cystatin S at all stages. Moreover, the gene expressions of TIMP-1 and -2, and of cystatins S and C, were predominant between 1 and 7, and 7 and 12 weeks of age, respectively, and coincided developmentally with the regression of terminal tubule cells and the differentiation of granular convoluted tubule cells, respectively. Quantitative competitive RT-PCR allowed accurate measurement of small changes in the steady-state concentrations of these proteinase-inhibitor mRNA molecules.

Abnormally high levels of cystatin S in submandibular glands, saliva, and gingiva of plaque-resistant rats

To identify salivary biomarkers of periodontal diseases, we used plaque-resistant and -susceptible rats as animal models. The levels of salivary cystatin S in saliva, salivary glands, and gingiva were tested in Nembutal-anesthetized young and adult plaque-resistant and -susceptible rats of both sexes with and without chronic treatment with isoproterenol. Isoproterenol was injected i.p. once a day for 4 or 6 consecutive days. Isoelectric focusing electrophoresis by the PhastSystem and the western blotting method were used to separate different proteins and to identify a salivary cystatin S band in these samples. The expression of salivary cystatin S mRNA was also determined by the northern blotting method. Depending upon the types of agonists, a few differences were observed in secretory functions between both strains of rats in both sexes, but the levels of salivary cystatin S in saliva elicited from the submandibular gland and in the extracts of the submandibular glands and gingiva were significantly higher in plaque-resistant rats when compared with those of plaque-susceptible rats in both sexes. However, no significant difference was seen between the strains after chronic treatment with isoproterenol. The N-terminal 26-amino-acid sequence of salivary cystatin S purified from submandibular saliva of plaque-resistant rats was identical with that purified from submandibular saliva of Sprague-Dawley rats subjected to chronic treatment with isoproterenol. The expression of salivary cystatin S mRNA was dramatic in the submandibular glands of the plaque-resistant rats and in the submandibular glands of Wistar rats subjected to chronic treatment with isoproterenol, but not in those of plaque-susceptible rats. These results suggest that salivary cystatin S might be a good biomarker in distinguishing between the two strains of rats and that its concentration is correlated with plaque resistance.

Isoproterenol-induced expression of the cystatin S gene in submandibular glands of parasympathectomized rats

Parasympathetic innervation of rat submandibular and parotid glands regulates saliva volume, its rate of secretion and its composition. It also has a regulatory role in hypertrophy and hyperplasia of salivary glands, and in the expression of specific sets of genes. Rat cystatin S is a member of family 2 of the cysteine proteinase inhibitor superfamily. Cystatin S gene expression is tissue- and cell type-specific, temporally regulated during postnatal development, and not observed in adult animals. Isoproterenol (IPR), a beta-adrenergic agonist, induces hypertrophic and hyperplastic enlargement of rat salivary glands and expression of a number of genes including cystatin S. Sympathectomy reduces, but does not completely block IPR-induced expression of the cystatin S gene in the submandibular glands of adult female rats, indicating the participation of sympathetic factor(s) in this regulation. Since both sympathetic and parasympathetic branches of the autonomic nervous system act in parallel in the submandibular gland, it is possible that parasympathetic nerve terminals also provide factor(s) that play a role in regulation of cystatin S gene expression. Experiments described in this paper were designed to test the hypothesis that the parasympathetic nervous system participates in IPR-induced cystatin S gene expression. Bilateral parasympathectomy reduced IPR-induced cystatin S gene expression, suggesting a role of the parasympathetic nervous system in its regulation. Unilateral parasympathectomy in contrast, had no effect on IPR-induced cystatin S gene expression, suggesting that the presence of an intact parasympathetic innervation in the contralateral side permits the 'normal' IPR-induced expression of the cystatin S gene in the parasympathectomized gland.

Production and characterization of two variants of human cystatin SA encoded by two alleles at the CST2 locus of the type 2 cystatin gene family

Two variants of cystatin SA encoded by two alleles at the CST2 locus of the type 2 human cystatin gene family were expressed in Escherichia coli. One, termed cystatin SA1, is identical to cystatin SA [S. Isemura, E. Saitoh, and K. Sanada J. Biochem. 102, 693-704, 1987]. Another, termed cystatin SA2, carries two amino acid substitutions (59Gly-->Asp; 120Glu-->Asp), one of which is in the so-called QXVXG region (the first hairpin loop) and another in the C-terminal portion of the molecule. Four recombinant cystatins [full-sized cystatin SA1, two N-terminally truncated cystatin SA1 lacking four residues (WSPQ) and six residues (WSPQEE), and full-sized cystatin SA2] were purified from the periplasmic fractions of E. coli cells. Two N-terminally truncated recombinant cystatin SA1 inhibited bovine cathepsin C with 2- to 20-fold lower Ki values than that of the full-sized one. In the inhibition of papain and ficin, however, both of the N-terminally truncated cystatin SA1 displayed a 10-fold higher Ki value than that of full-sized one. In the inhibition of papain, ficin, and recombinant human cathepsin K, recombinant cystatin SA2 showed, respectively, 3826-, 1090-, and 30-fold higher Ki values compared with those of SA1. Recombinant cystatin SA2 inhibited bovine cathepsin C with a 50-fold lower Ki value compared with that of SA1. Recombinant cystatin SA1 did not inhibit human cathepsin H but SA2 inhibited it slightly (Ki = 528 nM). Neither of the recombinant variants inhibited bovine cathepsin B. Our data supply evidence indicating that the amino acid sequence of the first hairpin loop of the cystatin superfamily is important in the inhibition of papain, ficin, cathepsin C, cathepsin H, and cathepsin K.

Production of rat salivary cystatin S variant polypeptides in Escherichia coli

Cystatins are protein inhibitors of papain and related cysteine proteinases. A series of continuous synthetic peptides corresponding to the entire sequence of rat salivary cystatin was used to localize the binding domains of the cystatin to papain. Several synthetic peptides, one from the aminoterminal sequence (peptide 1-24) and others from the carboxylterminal (peptides 66-79, 66-90, 79-90, 79-114), showed binding to papain, but none of the peptides showed inhibition of papain activity. Three recombinant rat salivary cystatin variants (N-terminal truncated protein lacking amino acid residues 1-9; variant 49-53, in which amino acid residues QVVAG of rat salivary cystatin had been replaced with amino acid residues LVL in mutant protein; and variant 65-78, in which amino acid residues 65-78 had been replaced with amino acids PG in mutant protein) were produced using the Escherichia coli expression system pGex-4T. To generate N-terminal truncated protein the desired coding region of the cystatin gene was amplified by polymerase chain reaction (PCR). To produce the variants 49-53 and 65-78, a PCR-based approach of gene splicing by overlap extension was used. Recombinant cystatin proteins were produced as insoluble inclusion bodies as fusion proteins with a glutathione S-transferase (GST) carrier. After solubilization with urea the GST carrier was cleaved from the fusion protein with thrombin and cystatin variants purified by fast liquid chromatography on a MonoQ column. The purified proteins reacted with antibodies to rat salivary cystatin. The N-terminal truncated and variant 49-53 exhibited very little inhibitory activity towards papain, whereas variant 65-78 exhibited papain-inhibitory activity similar to the full-length recombinant cystatin.

Examination of the potential structure of human salivary cystatins based on computer modelling

The cystatin family of proteins exists in both excreted and intracellular forms, and appears to be involved in protective and regulatory roles, inhibiting a variety of bacterial, viral and intracellular proteases. The amino acid sequences of several human forms of cystatin are known, but currently only the structure of chicken cystatin (approx. 40% homologous to the human forms) has been experimentally determined. The objective of this study was to use the X-ray coordinates of chicken cystatin to construct computer models of the structures of three human salivary forms (SN, S and SA). These structures were energy-minimized and subjected to dynamic simulations. The resultant structures were compared to determine conformational differences. Global root mean square deviations between equivalent atoms ranged from 1.4 A to 3.9 A. The closest structural similarity to chicken cystatin involved cystatin SN, which also showed the highest (68%) functional sequence homology. Local secondary structure was examined in more detail. In comparisons of alpha-carbon position the third beta-strand (77% functional sequence conservation) and its preceding loop (60% conserved) showed the highest structural conservation in S, while beta-strand 4 showed the highest structural conservation in SN and SA. Throughout their structures, SN and SA were more structurally similar to chicken cystatin than to salivary cystatin S. There are two regions of conserved, negatively charged residues in the salivary cystatins, which appear to be spaced so that they are capable of interaction with hydroxypatite. It is concluded that not only does structural modelling by analogy provide detailed models of salivary cystatins that can be tested by future experimentation, but also that examination of the models has revealed potential sites of interaction with hydroxyapatite.

Cystatin A in gingival crevicular fluid of periodontal patients

Cystatins are physiological inhibitors of cysteine proteinases which are widely distributed in human tissues and fluids. In the present study we analysed both the cystatin activity and the different cystatin isoforms in gingival crevicular fluid and saliva samples of nine periodontitis patients. All crevicular fluid samples, which were collected with filter paper points, showed cystatin activity ranging from 7-67 units/mg protein. The mean cystatin activity (24 units/mg protein) was significantly lower (p < 0.05) than that of the saliva samples (mean 93 units/mg protein). The cystatin isoforms in the crevicular fluid were further characterized by immunoblotting with specific antibodies against cystatin C, S, SN and A. While they were clearly present in saliva, cystatin C, cystatin S and cystatin SN could not be detected in any of the crevicular fluid samples. Remarkably, cystatin A was found in all the crevicular fluids as well as in the saliva samples. It is concluded that the cystatin activity found in crevicular fluid is caused, at least partially, by cystatin A. Furthermore, the gingival crevicular fluid is not a major contributor of cystatin C, S and SN activity in saliva.

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.

Characterization of human sublingual-gland protein kinase by phosphorylation of a peptide related to secreted proteins

Phosphoproteins in human saliva include proline-rich proteins, statherins, histatin 1 and cystatin SA-III. The presence of phosphate in these proteins is necessary for various functions in the mouth including calcium binding, inhibition of precipitation of calcium phosphate, inhibition of growth of hydroxyapatite crystals and adherence to hydroxyapatite. To elucidate the process of phosphorylation of these proteins, the phosphorylation of a peptide (APRP8) with an amino acid sequence identical to one of the phosphorylated sites in acidic proline-rich proteins by a kinase from the human sublingual gland was investigated. The kinase, which was highly labile, was purified 58-fold by fractionation of sublingual gland homogenate and gel filtration, but the enzyme was inactivated when further purification by chromatographic techniques commonly used for protein kinases was attempted. To compare the enzyme with other kinases, and to obtain information that could be used in its further purification, a characterization was undertaken. The enzyme required 10 mM Mg2+ for optimum activity, it had a KM of 0.09 mM for ATP and the KM for the peptide substrate APRP8 was 0.42 mM. It was not activated by cAMP or calmodulin, characteristics that are shared with casein kinases and mammary gland kinase. The sublingual kinase as well as casein kinase 2 were inhibited by heparin, but in other respects the two kinases had different properties. While casein kinase 2 is activated by polylysine and has optimal activity in 150 mM KCl, sublingual kinase was inhibited by polylysine and the addition of KCl. Moreover, casein kinase 2 can utilize both ATP and GTP as phosphoryl donors, but GTP was not a substrate for sublingual kinase. The sublingual kinase shared a substrate recognition sequence with mammary gland kinase, but, unlike that kinase, it could not utilize Ca2+ instead of Mg2+. While the sublingual kinase thus shared some properties with both casein kinase 2 and mammary gland kinase, distinct differences were also seen and the relationship to these enzymes remains to be determined. The characterization of the sublingual kinase will be useful in its further purification.

Immunocytochemical study of cathepsin L and rat salivary cystatin-3 in rat osteoclasts treated with E-64 in vivo

The localization of cathepsin L and rat salivary cystatin-3 (RSC-3) in rat osteoclasts (rat femoral and alveolar bones) treated with or without E-64 (control) was examined immunocytochemically. In osteoclasts pretreated with E-64, immunoreactivity for cathepsin L was very weak extracellularly compared to that in the control osteoclasts. However, it was strong intracellularly. The localization of RSC-3 was unclear in the control osteoclasts, while in E-64 treated osteoclasts, both the clear zone and ruffled border areas showed a very strong immunoreaction. At the electron-microscopic level, in normal osteoclasts, numerous immunoreaction products for cathepsin L were found extracellularly in the bone matrix under the ruffled border, while few intracellular products were observed. In contrast, in the E-64-treated osteoclasts, only a few immunoreaction products were found extracellularly, while intracellularly cathepsin L was found in numerous endosome-lysosomal vacuoles. In the immunoreaction for RSC-3, the cytoplasm of the ruffled border was positive, and the tips of the RSC-3-positive ruffled border appeared to enter deeply into the bone matrix. Intracellularly, the granular reaction products of RSC-3 were found in the vacuoles (probably autophagolysosomes). Thus, in E-64-treated osteoclasts, inhibition of the extracellular release of cathepsin L was demonstrated. In addition, intralysosomal accumulation of RSC-3 and deep penetration of the RSC-3-positive ruffled border into the bone matrix were found. These findings suggest that RSC-3 is associated with the inhibition of cathepsin L in both the lysosomes (in the osteoclasts) and bone matrix.

The effect of methotrexate on the expression of a cysteine protease inhibitor (type 2 cystatin) in rat sebaceous glands

The purpose of this study was to assess whether rat cystatin S, a cysteine proteinase inhibitor, is present in rat sebaceous glands, and to measure the effects of methotrexate on the expression of cystatin in these glands. With methotrexate treatment, the number of skin sebaceous cells expressing cystatin increased from 13.9% to 34.3% (P < .05). A smaller increase (from 15.3% to 23.9%; P = .1) was observed in Zymbal sebaceous glands. Type 2 cystatin could not be detected in the major salivary glands, nor in trachea, lung, stomach, small intestine, large intestine, spleen, liver, kidney, or pancreas, in any of the rats given either saline or methotrexate. Our results suggest that type 2 cystatin is a constituent of normal sebaceous glands, and that the amount of cystatin present in these glands increases with methotrexate administration. We speculate that, in addition to the protective functions ascribed to sebaceous lipids, sebum may augment the physical barrier of skin through secretion of cysteine proteinases that may be pharmacologically modulated.

Inhibition of the growth and cysteine proteinase activity of Porphyromonas gingivalis by human salivary cystatin S and chicken cystatin

The mutual effects of P. gingivalis and several cystatin species has been investigated. After incubation with P. gingivalis culture supernatant, cystatin S, cystatin C and chicken cystatin were truncated from a 14 kDa protein into a polypeptide of approximately 13 kDa. Amino acid sequence analysis of the truncated cystatin S polypeptide revealed that cystatin S was cleaved after Arg-8. All three types of truncated cystatins fully retained their inhibitory activity toward papain. Cystatin S and chicken cystatin partially inhibited proteolytic activity in the culture supernatant of P. gingivalis. Furthermore, cystatin S and chicken cystatin inhibited the growth of P. gingivalis in culture to 50% at approximately 1 microM.

Growth inhibition of a human oral bacterium Porphyromonas gingivalis by rat cysteine proteinase inhibitor cystatin S

Agar diffusion analysis demonstrated that rat cystatin S, a cysteine proteinase inhibitor, inhibited the growth of all tested strains of a human oral, Gram-negative anaerobic periodontopathogen Porphyromonas gingivalis. Its specific inhibitory activity against this tissue-invasive bacterium but not against other tested oral bacterial species emphasized the importance of specific cysteine proteinases for growth of P. gingivalis.

Salivary protein composition in epileptic patients on different medications

Several salivary proteins were assayed in saliva from epileptic patients who were using different anti-epileptic drugs, viz, phenytoin, valproate and carbamazepine, and were compared with levels in unmedicated healthy control subjects. Flow rate and pH of the patient groups were not different from the controls. In all patient groups the specific amylase activity was increased up to twofold. In the phenytoin group only, the salivary IgA concentration was strongly reduced. Levels of salivary cystatin C were similar among all patient groups studied, and were not different from those of the control group. In contrast, the absolute and relative concentrations of cystatin S were diminished, particularly in patients using either valproate or phenytoin. These data suggest that use of anti-epileptic drugs over long periods may result in decreased levels of several salivary proteins such as sIgA and cystatins, which are involved in the protection of the oral cavity against microbial infections.

Human glandular salivas: their separate collection and analysis

Human saliva is secreted by the three pairs of major salivary glands (parotid, submandibular, and sublingual), and numerous minor ones, e.g. labial, buccal and (glosso)palatine glands. Using individually adapted collection devices, sublingual, submandibular, parotid and palatine secretions of five individuals were collected and analyzed. Electrophoretic analysis revealed that each type of saliva possesses characteristic features, despite interindividual variations. Parotid salivas are characterized by intensely staining amylase and proline-rich protein bands, but contain minute amounts of cystatins, lysozyme and the extra-parotid glycoprotein. Sublingual salivas are characterized by high concentrations of both types of salivary mucins, MG1 and MG2, and contain relatively high levels of lysozyme. Submandibular salivas contain highest concentration of salivary cystatin S. Palatine secretions contain high molecular weight mucins and a relatively high amylase concentration.

Analysis of the concentration and output of whole salivary constituents in patients with Sjögren's syndrome

In Sjögren's syndrome, salivary glands are affected, resulting in a diminished salivary flow. In the present study, the protein composition, sialic acid content and the amounts of calcium and phosphate of stimulated whole saliva from 43 patients with Sjögren's syndrome, were compared with those of control saliva samples from 17 healthy subjects. The absolute concentrations of albumin, cystatin C, cystatin S, total IgA and total protein, but not amylase, were increased significantly in both primary and secondary Sjögren's syndrome. The output/min of total protein, albumin, amylase, and IgA was, however, decreased in Sjögren patients. These results suggest that the diminished output of salivary defence factors, rather than their absolute concentrations, may be related to the oral health problems seen in Sjögren's syndrome patients.

Effect of periodontal treatment on the protein composition of whole and parotid saliva

Cystatins are physiological inhibitors of cysteine proteinases and widely distributed in human tissues and fluids including saliva. Cystatins S, SA, SN, and D are only found in glandular saliva and tear fluid whereas cystatin C has been detected in all tested biological fluids. Previous studies demonstrated that total cystatin activity and cystatin C concentration were highest in whole and parotid saliva of periodontitis patients compared to healthy subjects suggesting a response of the salivary glands to an inflammatory condition of the oral cavity. Based on these results we studied a possible change in the concentration of cystatin S, cystatin C, albumin, IgA, amylase activity, and cystatin activity in a whole and parotid saliva of 20 periodontitis patients as a consequence of periodontal treatment. Saliva samples were quantified for cystatins S and C, albumin, and IgA by enzyme-linked immunosorbent assay. Amylase was determined in an activity assay and total cystatin activity was measured towards pa-pain. The clinical condition of the subjects improved significantly after 6 months of periodontal therapy whereas biochemical analyses of whole and parotid saliva indicated that significant changes in salivary protein composition occurred only in whole saliva. Total cystatin activity (P < 0.05) and cystatin C concentration (P < 0.05) of whole saliva samples collected after periodontal treatment decreased to normal healthy control values. Further, concentrations of cystatin S were unchanged during the periodontal treatment process. These results suggest that other sources of cystatins than the parotid gland i.e.; other salivary glands or crevicular fluid, are involved in the decrease of total cystatin activity in whole saliva after periodontal treatment.

Expression of a functional rat salivary cystatin S polypeptide in Escherichia coli

Cystatin S is a cysteine proteinase inhibitor that is transiently expressed during rat submandibular gland development and can be induced by isoproterenol in the adult. A cDNA for rat cystatin S which included the entire coding sequence of the secreted cystatin was cloned. A coding region of the cystatin gene was amplified by polymerase chain reaction and cloned into the pGEX-2T expression vector. The chimeric plasmid was transformed into Escherichia coli, and protein expression was induced by isopropyl-beta-D-thiogalactopyranoside. The expressed protein was purified from insoluble inclusion bodies after solubilization with urea and fast protein liquid chromatography on a MonoQ column. The purified recombinant cystatin reacted with antibodies to cystatin S purified from rat submandibular glands and showed an amino-terminal amino acid sequence identical to that of rat cystatin S. The recombinant protein exhibited papain inhibition activity comparable to natural cystatin. This was a successful expression and purification of a functionally and immunologically reactive recombinant cystatin from E. coli, an approach which will be used later towards generating recombinant variants to study the binding and functional domains of this cysteine protease inhibitor.

Cystatin S in secretory granules fractions isolated from submandibular gland of infected rats by Trypanosoma cruzi

We have measured the relative concentrations of cysteine proteinase in the granular fractions of submandibular glands of control and Trypanosoma cruzi infected rats by using a sensitive solid phase ELISA. Gland samples were homogenized in 0.34 M sucrose and 0.5 mM EDTA in 10 mM HEPES buffer at a pH of 7.4. The extract was centrifuged and filtered through Millipore filters to prepare a purer granular fraction. Immunochemical studies using antibody against cystatin S and electrophoretic analysis showed higher cystatin S levels in infected rats than in control. The role of this inhibitor during acute phase of Chagas disease is discussed.

Bactericidal effect of rat cystatin S on an oral bacterium Porphyromonas gingivalis

We tested antibacterial and antiviral activities of rat cystatin S, a cysteine proteinase inhibitor, belonging to the family 2 cystatins against 18 different bacterial species and poliovirus type 1 (Sabin). Rat cystatin S specifically inhibited the growth of a human oral anaerobic bacterium Porphyromonas gingivalis due to a bactericidal effect.

Biological activities and secondary structures of variant forms of human salivary cystatin SN produced in Escherichia coli

Using an Escherichia coli expression system, pGEX-2T, that expresses foreign sequences as fusion proteins with a glutathione S-transferase (GST) carrier, we have produced several recombinant human salivary cystatin SN (reCsnSN) variants. These include a N-terminal-truncated form (aa 17-121), a C-terminal-truncated form (aa 1-102) and two deletion mutants (delta 12-16 and delta 56-60). A large amount of the insoluble fusion protein (approx. 15 mg/l) was produced in each case. These were solubilized with urea and refolded by dialysis. The GST carrier was then cleaved with thrombin and the reCsn variants (except delta 56-60) were purified by anion-exchange chromatography. The CysP inhibitory activities against papain, and bovine and human cathepsin B, and secondary structures of the reCsnSN variants were determined and compared to natural salivary CsnSN. The full-length reCsnSN, the N-truncated and the delta 12-16 variants inhibited the CysP activity of papain and displayed circular dichroism (CD) spectra similar to that of natural CsnSN. On the other hand, the delta 56-60 mutant and the C-truncated variant exhibited very little inhibitory activity towards papain. The CD spectrum of the C-truncated variant indicated a change in the secondary structure (e.g., a decrease in beta-sheet and an increase of an alpha-helical content). Neither, the natural nor the full-length reCsnSN or the delta 12-16 mutant exhibited any inhibitory activity towards bovine and human cathepsin B.

Glossopharyngeal denervation alters responses to nutrients and toxic substances

Functional roles of the glossopharyngeal (GL) nerve on food and fluid intake were studied by examining effects of the GL denervation on two biologically different activities induced by specific diets using mice and rats. First, we examined whether GL section alters the acceptability of a bitter tasting essential amino acid, L-lysine (Lys), by Lys-deficiency in mice. The aversion threshold for Lys, normally about 3 uM in mice, increased to about 300 uM when mice were fed the Lys-deficient diet for 10 days. This increase of the Lys aversion threshold (increase of acceptability for Lys) by Lys-deficiency was also evident in mice with the chorda tympani denervation but was not observed in mice with the GL denervation. Next, we examined whether GL section alters the induction of a salivary protein, cystatin S (a cysteine proteinase inhibitor), by a diet containing papain (a cysteine proteinase) in rats. GL denervation largely inhibited the induction of cystatin S in the rat submandibular glands by papain. These results collectively suggest that chemosensory information conveyed by the GL nerve plays important roles on recognition of both nutrient and toxic compounds in the diet and induction of biological responses that protect the animal from both nutritional deficiency and exogenous toxic compounds.

Production of human salivary type cysteine proteinase inhibitors (cystatins) by an Escherichia coli system and partial characterization of recombinant cystatin S and its mutant (117 arginine-->tryptophan)

The cDNAs encoding the precursors of cystatin SN, cystatin S, and two mutants of cystatin S (-18R-->W; 117R-->W) were expressed in Escherichia coli JM109 with isopropyl-beta-D-thio-galactoside (IPTG) induction. Premature cystatin S with the original signal [-20MARPLCTLLLLMATLAGALA] was processed and a large amount of the mature form was produced. A mutation (-18R-->W) in the signal reduced its accumulation in periplasmic space remarkably. The amount of cystatin SN accumulated in the periplasm was slightly smaller than that of cystatin S. The periplasmic fraction was prepared by cold osmotic-shock treatment and the expressed cystatins were detected using anti-cystatin S antibody. Recombinant cystatin S and its mutant (117R-->W) were purified from the periplasmic fractions with an ion exchange column of DEAE-cellulose. The amino (N-) terminal 10 residues of recombinant cystatin S was sequenced to be SSSKEENRII-, which is exactly identical to that of the authentic mature cystatin S. Recombinant cystatin S and the mutant showed virtually the same inhibitory properties for ficin, papain and cathepsin B as the native cystatin S and its monophosphorylated form. The inhibitory activity of the both recombinant cystatins for cathepsin C was weaker than those of the native cystatin S and phosphorylated cystatin S.

Genetic polymorphisms of the CST2 locus coding for cystatin SA

A new genetic polymorphism of cystatin SA has been identified in human submandibular-sublingual saliva by means of basic gel electrophoresis and immunoblotting with anti-cystatin S. Two proteins, SA1 and SA2, are given by two alleles of CST2, viz., CST2*1 and CST*2. Inheritance is controlled by two codominant alleles at an autosomal locus. This hypothesis is supported by studies of 16 families 32 children. Gene frequencies for CST2*1 and CST2*2 are 0.935 and 0.065, respectively (n = 341). Eighteen amino acids determined among 20 N-terminal residues of cystatin SA2 are identical with the sequence encoded by CST2. Three forms of cystatin S (mono-phosphorylated cystatin S, di-phosphorylated cystatin S, and non-phosphorylated cystatin S) are present in the 341 saliva samples tested.

Induction of synthesis of the rat cystatin S protein by the submandibular gland during the acute phase of experimental Chagas disease

Rats experimentally infected with Trypanosoma cruzi Y strain exhibited hypertrophy of the submandibular gland at 18 days after infection. SDS-PAGE of infected rats saliva revealed the presence of an additional band with an apparent molecular weight of about 13KDa. Electrophoresis of protein saliva and immunochemical analysis with antibody against rat cystatin S confirmed that the protein was identical to that induced by beta adrenergic stimulation.

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.

Induction of cystatin S in rat submandibular glands by papain

1. Papain (a cysteine proteinase) were administered into the oral cavity of rats twice daily for 5 days. This treatment caused a dramatic increase in the level of cystatin S (a cysteine proteinase inhibitor belonging to family 2 of cystatin superfamily) in enlarged submandibular glands. 2. Immunochemical analysis using antibody against rat cystatin S and electrophoretic analysis confirmed that the protein induced by papain was identical to that induced by isoproterenol. 3. Induction of the cystatin S in the submandibular glands by oral administration of papain suggested a biological response which plays a role in preventing injury exogenous proteinase.

Formation of salivary-mucosal pellicle: the role of transglutaminase

The present investigation was carried out to identify salivary components of mucosal pellicles in vivo and explore further the mechanism of interaction between salivary molecules and buccal epithelial cells. By using specific antisera and immunoprotein blotting, high-(MG1) and low-(MG2) molecular-mass salivary mucins, amylase, salivary cystatins and proline-rich proteins were detected within mucosal pellicle in vivo. In addition, the data indicated that the mucins and proline-rich proteins could be cleaved into lower-molecular-mass products, whereas the proline-rich proteins could also be cross-linked into higher-molecular-mass complexes. The role of buccal epithelial cell transglutaminase in these interactions was further studied by utilizing purified iodinated amylase, neutral cystatin SN and acidic proline-rich proteins 1 and 3 (APRP1 and 3). After incubation with buccal epithelial cells in vitro 125I-labelled APRPs appeared to undergo a greater degree of cross-linking than 125I-labelled cystatin SN, as determined by SDS/PAGE/autoradiography. Amylase did not appear to be cross-linked at all. Recovery of 125I-labelled APRPs and 125I-labelled cystatin SN with epithelial cell envelopes after repeated extraction suggested that both molecules were cross-linked to envelope proteins, but that 125I-labelled APRPs were cross-linked to a greater degree than 125I-labelled cystatin SN. Cross-linking in buccal epithelial cell preparations was inhibited by an excess of methylamine hydrochloride, a transglutaminase substrate. In a further assessment of amylase, cystatin and APRPs as transglutaminase substrates, only APRP3 and a partially purified preparation of APRPs acted as an amine acceptor for the cross-linking of [14C]methylamine by purified transglutaminase, as determined by SDS/PAGE/fluorography. This reaction was completely inhibited by excess EDTA. The combined data from this study suggest that during mucosal pellicle formation multiple components of saliva adsorb to buccal epithelial cell surfaces, and that, within this group, selected components are enzymically cross-linked by an epithelial transglutaminase and/or proteolytically cleaved into smaller fragments.

Structure, organization and regulation of a rat cysteine proteinase inhibitor-encoding gene

During postnatal development, submandibular glands of rats produce the secretory protein, cystatin S (CysS), which belongs to family 2 of the mammalian cysteine proteinase inhibitor superfamily. While the rat CysS gene is not expressed in the salivary glands of adult rats, it can be induced by isoproterenol (IPR), which acts via beta-adrenergic receptor/adenylate cyclase/cyclic AMP (cAMP) mechanisms. In addition, IPR-induction of CysS mRNA in submandibular glands is more pronounced in females than in males, at both prepuberal and mature ages. These results suggest that sex hormones may participate in the regulation of the rat CysS gene via estrogen-responsive elements (ERE), and IPR induction of this gene supports the hypothesis that cAMP-responsive elements (CRE) may also play a role in regulating CysS gene expression. We have isolated, sequenced and characterized the complete gene. The CysS gene contains three exons interrupted by two intervening sequences, with consensus splice junctions. The transcription start point is 73 nucleotides upstream from the start codon which is surrounded by a typical Kozak sequence. CCAAT and TATA boxes are present in the 5'-flanking region of the CysS gene. This region also contains several possible regulatory elements that resemble those of other eukaryotic genes, i.e., ERE, CRE, and glucocorticoid-responsive elements. The first intron sequence contains other potential CRE highly homologous to those found in the IPR-inducible mouse and hamster proline-rich-protein-encoding genes.