Genetic polymorphism of basic proteins from parotid saliva

Effects of histatin 5 modifications on antifungal activity and kinetics of proteolysis

Histatin 5 (Hst-5) is an antimicrobial peptide with strong antifungal activity against Candida albicans, an opportunistic pathogen that is a common cause of oral thrush. The peptide is natively secreted by human salivary glands and shows promise as an alternative therapeutic against infections caused by C. albicans. However, Hst-5 can be cleaved and inactivated by a family of secreted aspartic proteases (Saps) produced by C. albicans. Single-residue substitutions can significantly affect the proteolytic resistance of Hst-5 to Saps and its antifungal activity; the K17R substitution increases resistance to proteolysis, while the K11R substitution enhances antifungal activity. In this work, we showed that the positive effects of these two single-residue modifications can be combined in a single peptide, K11R-K17R, with improved proteolytic resistance and antifungal activity. We also investigated the effect of additional single-residue substitutions, with a focus on the effect of addition or removal of negatively charged residues, and found Sap-dependent effects on degradation. Both single- and double-substitutions affected the kinetics of proteolytic degradation of the intact peptide and of the fragments formed during degradation. Our results demonstrate the importance of considering proteolytic stability and not just antimicrobial activity when designing peptides for potential therapeutic applications.

Protein-Based Salivary Profiles as Novel Biomarkers for Oral Diseases

The Global Burden of Oral Diseases affects 3.5 billion people worldwide, representing the number of people affected by the burden of untreated dental caries, severe periodontal disease, and edentulism. Thus, much more efforts in terms of diagnostics and treatments must be provided in the fight of these outcomes. In this sense, recently, the study of saliva as biological matrix has been identified as a new landmark initiative in the search of novel and useful biomarkers to prevent and diagnose these conditions. Specifically, saliva is a rich reservoir of different proteins and peptides and accessible due to recent advances in molecular biology and specially in targeted and unbiased proteomics technologies. Nonetheless, emerging barriers are an obstacle to the study of the salivary proteome in an effective way. This review aims at giving an overall perspective of salivary biomarkers identified in several oral diseases by means of molecular biology approaches.

Histatins, wound healing, and cell migration

Wounds in the oral mucosa heal faster and more efficiently than those in the skin, although the mechanisms underlying these differences are not completely clear. In the last 10 years, a group of salivary peptides, the histatins, has gained attention on behalf of their ability to improve several phases of the wound-healing process. In addition to their roles as anti-microbial agents and in enamel maintenance, histatins elicit other biological effects, namely by promoting the migration of different cell types contained in the oral mucosa and in non-oral tissues. Histatins, and specifically histatin-1, promote cell adhesion and migration in oral keratinocytes, gingival and dermal fibroblasts, non-oral epithelial cells, and endothelial cells. This is particularly relevant, as histatin-1 promotes the re-epithelialization phase and the angiogenic responses by increasing epithelial and endothelial cell migration. Although the molecular mechanisms associated with histatin-dependent cell migration remain poorly understood, recent studies have pointed to the control of signaling endosomes and the balance of small GTPases. This review aimed to update the literature on the effects of histatins in cell migration, with a focus on wound healing. We will also discuss the consequences that this increasing field will have in disease and therapy design.

Diagnostic model of saliva peptide finger print analysis of oral squamous cell carcinoma patients using weak cation exchange magnetic beads

Whole saliva (WS) was used for diagnosis of oral squamous cell carcinoma (OSCC); two polypeptides may be used for OSCC diagnosis.

Saliva diagnostics utilizing nanotechnology and molecular technologies to detect oral squamous cell carcinoma (OSCC) has become an attractive field of study. However, no specific methods have been established. To refine the diagnostic power of saliva peptide fingerprints for the early detection of OSCC, we screened the expression spectrum of salivary peptides in 40 T1 stage OSCC patients (and healthy controls) using MALDI-TOF-MS combined with magnetic beads. Fifty proteins showed significantly different expression levels in the OSCC samples (P<0.05). Potential biomarkers were also predicted. The novel diagnostic proteomic model with m/z peaks of 1285.6 Da and 1432.2 Da are of certain value for early diagnosis of OSCC.

A new method for the isolation of histatins 1, 3, and 5 from parotid secretion using zinc precipitation

Histatins, a family of small-molecular-weight, histidine-rich cationic salivary proteins, have been difficult to isolate in an efficient way by conventional procedures due to their anomalous interactions with chromatographic resins. In the present study we explored the possibility of developing a new isolation procedure based on recent observations that histatins associate with various metal ions, including zinc. Since solubility studies showed that histatin 5 forms precipitates with zinc under alkaline conditions, we investigated whether this characteristic could be exploited for the preparative isolation of histatins from salivary secretions. A fast and efficient two-step procedure was developed using zinc precipitation of histatins from human parotid secretion followed by final purification using reversed-phase high-performance liquid chromatography (HPLC). Analysis of zinc precipitates by Tricine-SDS-PAGE, cationic PAGE, HPLC, and mass spectrometry revealed the presence of the three major histatins, 1, 3, and 5, as well as statherin. The histatin yield obtained by the precipitation step was approximately 90%. Therefore, zinc precipitation of histatins from glandular salivary secretions is a novel, rapid, and effective means for the isolation of these proteins.

Human salivary histatins: promising anti-fungal therapeutic agents

Histatins constitute a group of small, cationic multifunctional proteins present in the saliva of human and some non-human primates. The most significant function of histatins may be their anti-fungal activity against Candida albicans and Cryptococcus neoformans. Histatins have been extensively studied at both the protein and gene levels. The structure-function relationship of histatins with respect to their candidacidal activity has also been studied by means of recombinant histatin variants, as well as by chemically synthesized histatin fragments. The mechanism of histatins' action on Candida albicans is not clear, but it appears to be different from that of azole-based anti-fungal drugs which interrupt ergosterol synthesis. During the past 20 years, fungal infections have become more prevalent as a result of the emergence of AIDS, as well as, paradoxically, modern medical advances. The toxicity of current anti-fungal medicine, the emergence of drug-resistant strains, and the availability of only a few types of anti-fungal agents are the major disadvantages of current anti-fungal therapy. Therefore, the importance of the search for new, broad-spectrum anti-fungals with little or no toxicity cannot be overemphasized. The following properties make histatins promising anti-fungal therapeutic agents: (1) They have little or no toxicity; (2) they possess high cidal activities against azole-resistant fungal species and most of the fungal species tested; and (3) their candidacidal activity is similar to that of azole-based antifungals. Current research efforts focus on the development of improved histatins with enhanced cidal activity and stability, and of suitable and effective histatin delivery systems. These and other approaches may help to outpace the growing list of drug-resistant and opportunistic fungi causing life-threatening, disseminating diseases. The histatins with improved protective properties may also be used as components of artificial saliva for patients with salivary dysfunction.

Two coding change mutations in the HIS2(2) allele characterize the salivary histatin 3-2 protein variant

The decoded amino acid sequence of a salivary protein variant, histatin 3-2 (formerly termed Pb c), that is found primarily and in high frequency in Black populations was determined by genomic PCR and direct sequencing of the HIS2(2) allele. Two different mutations that cause coding changes were found in exon 5. The first mutation is a single nucleotide (T-->A) substitution that causes a TAT (Tyr)-->TAA (Stop) change at residue 28. This premature stop mutation results in a 27 amino acid histatin 3-2 protein, which is 5 amino acids smaller than the common histatin 3-1 allelic protein (a product of the HIS2(1) allele). The second mutation, a single nucleotide (G-->A) substitution (located only 19 nucleotides upstream of the first mutation) causes a CGA (Arg)-->CAA (Gln) change at residue 22, which eliminates a proteolytic cleavage site. These two mutations explain the differences in electrophoretic patterns of HIS2(1) versus HIS2(2) coded histatin peptides and may have functional significance. Each mutation alters a different DNA restriction site, and this provides a DNA-based test for the mutations. This test should greatly simplify population and family studies of this protein polymorphism, since the saliva-based test is considerably more problematic. Elucidation here of the derived protein sequence of the variant histatin 3-2 protein may also facilitate functional studies.

High-performance liquid chromatographic determination of histatins in human saliva

A simple method for the assay of histatins in human saliva by high-performance liquid chromatography has been developed. The histatins in saliva were extracted with 0.1 M HCl-methanol, and histatins 1, 3, 5, and 6 were separated and concentrations were determined by reversed-phase chromatography. This simple method enabled the determination of levels of individual histatins from the saliva of normal subjects. The average concentration of histatins 1, 3, 5, and 6 in parotid saliva collected from 26 healthy volunteers aged from 20 to 30 years were 11.25 +/- 5.65, 8.15 +/- 3.08, 7.67 +/- 3.12, and 1.56 +/- 0.53 mumol/l (mean +/- S.D.), respectively.

Tissue distribution of RNAs for cystatins, histatins, statherin, and proline-rich salivary proteins in humans and macaques

The tissue distribution of the mRNAs for a number of salivary proteins [proline-rich proteins (PRPs), statherin, cystatins, and the histatins] has been examined in humans and macaques in order to investigate their possible functions and tissue-specific regulation. We have shown that PRP RNAs (0.8-1.5 kb) are expressed in human and rhesus parotid and submandibular glands, and in the human bronchus. The genes for the acidic and basic PRPs are differentially regulated in these tissues. RNAs for acidic PRPs are predominantly expressed in the submandibular gland, for basic PRPs in the respiratory tract, and for both acidic and basic PRPs in the parotid gland. Protein studies of secretions from these tissues confirm the RNA results. Statherin RNA (0.65 kb) was detected in human and rhesus parotid and submandibular glands and the human bronchus, as well as in rhesus lacrimal glands. Statherin was found by tissue immunoperoxidase staining in the serous cells of respiratory tract submucosal glands, which is the same location for the synthesis of PRPs. Several cystatin RNAs (0.8-1.3 kb) were differentially expressed in human parotid glands, submandibular glands, and the bronchus, and in lacrimal glands from both rhesus and cynomolgus macaques. RNAs (0.6 kb) for the histatins were found only in parotid and submandibular glands. Thus, it appears that PRPs, statherin, and cystatins may play a broader role in the physiology of biological fluids and secretions than previously suspected, since they are found in secretions other than saliva. However, the functions of the histatins are restricted to saliva. These studies also pose some interesting questions regarding the differential expression of these genes in a variety of secretory tissues.

Histatins, a family of salivary histidine-rich proteins, are encoded by at least two loci (HIS1 and HIS2)

We screened a human parotid gland cDNA library with mixed synthetic oligonucleotide probes representing a central coding region common to histatins 1 and 3. Sequence analysis of 12 histatin cDNA clones strongly suggests that the histatin protein family is encoded by at least two closely related loci (HIS1 and HIS2) such that histatins 1 and 3 are primary products of HIS1(1) and HIS2(1) alleles, respectively, and that histatins 4-6 are derived from histatin 3 by proteolysis. We present additional data indicating that histatin 2 may represent the non-phosphorylated form of histatin 1.

Genetic polymorphisms of the Pmo1 and Pmo2 salivary proteins detected by the modified protein staining method

Two polymorphic proteins, Pmo1 and Pmo2, were found in human parotid saliva by modifying the protein staining method of Sung & Smithies (1969). The inheritance of each polymorphism was controlled by a dominant allele at an autosomal locus. This hypothesis was supported by studies in 50 families including 103 children. The gene frequencies were Pmo1+ = 0.308, Pmo1- = 0.692, Pmo2+ = 0.026, Pmo2- = 0.974. The Pmo1 and Pmo2 proteins reacted immunologically with antisera prepared to salivary proline-rich proteins (Pr and Gl). The isoelectric point was in excess of 8.58. These results showed that the Pmo1 and Pmo2 proteins belong to the basic proline-rich proteins in human parotid saliva.

Further evidence for phenotypes and gene frequencies of nine salivary polymorphisms in Japanese population

Nine salivary polymorphic systems (Pa, Pb, Pr, Db, PmF, PIF, Ph, Amy1 and s-AcP) were examined using parotid and whole saliva from random Japanese individuals. The gene frequencies obtained were: Pa+ = 0.221, Pb1 = 1.000 Pr1 = 0.741, Db+ = 0.033, PIF+ = 0.715, Ph+ = 0.029, Amyv1 = 0.013 and s-AcPA = 0.217, respectively.

Sex and strain differences of mouse variant salivary proteins

Proteins of the mouse saliva are resolved into about 20 discrete bands by polyacrylamide gel electrophoresis. Sexual dimorphism and monomorphism were found in a subset (Msp-1) of these salivary proteins from different inbred strains. This sexual dimorphism involves a fast moving band (F-type) and a slow moving one (S-type). Mature males of seven strains (A/J, AKR, CBA/J, C3H/HeN, A/Sn, B10.A, and B10.BR) exhibit the S phenotype while mature females of these strains were typed as F. Sexually immature males and females of these strains were uniformly typed as F, but at puberty (5-6 weeks of age) the phenotype of the males switched to type S, while the phenotype of the females remained the same. This switch to type S at puberty did not take place in males of four strains (BALB/cAnn, B10.D2, C57BL/6, and C57BL/10); therefore, we conclude that these strains were sexually monomorphic with regard to Msp-1. The phenotype of mature males of C3H/HeN reverted to type F following castration, whereas castrated males and mature females switched to type S in response to testosterone administration. The testosterone treatment had no effect on the type S phenotype of males and females of the sexually monomorphic BALB/cAnn strain. The male-specific type S phenotype of Msp-1 was seen only in mice with H-2 haplotype a or k; thus an association with H-2 haplotype was suggested. All F1 males of reciprocal crosses involving the sexually dimorphic and monomorphic strains (e.g., C3H/HeN X BALB/cAnn) demonstrated the type S phenotype at puberty.

Salivary protein polymorphisms in caries-free and caries-active adults

Several salivary proteins are known to exhibit genetic polymorphism, and this study was undertaken to determine whether there was an association of caries experience with specific parotid salivary protein phenotypes. Parotid saliva collected from 46 caries-free and 47 caries-active naval recruits was subjected to SDS, anionic, and cationic polyacrylamide slab gel electrophoresis. Distributions of the acidic proline-rich (Pr), parotid acidic (Pa), double band (Db), parotid size variant (Ps), parotid middle band (Pm), and parotid basic (Pb) protein phenotypes were similar in both caries-free and caries-active subjects. Further, overall protein patterns on SDS, anionic, and cationic slab gels did not differ between the two groups.

Frequencies of salivary genetic marker systems in Caucasians with an emphasis on Pm and Ph systems

Salivary genetic marker systems, especially the Pm and Ph systems, were studied in Caucasians. The gene frequencies obtained were, Pm+ = 0.14 and Pm- = 0.86. A variant polymorphic protein (Ph) present in the Japanese population was not observed in Caucasians.

Genetic variation in parotid basic proteins (Pb) in the Bozo (Mali, West Africa)

The frequency of variants in the Pb system was studied in 71 individuals from the Bozo tribe in the Bani-Niger area (Mali, West Africa), in 25 male students from different African countries, and in 110 Dutch students. The frequency of the Pb2 allele was 0.20 in the Bozo and 0.00 in the Dutch population. A comparison is made with the results of a study among American blacks and with a Japanese study. The Pb 2--2 phenotypes observed in this study favour the hypothesis that the Pb-2 c protein is derived from a larger precursor in a manner analogous to the generation of the Pb-1 b protein from Pb-1 protein e.

Determination of phenotypes of esterases (Set) in fresh saliva and saliva stains by disc electrophoresis and the distribution of Set phenotypes in the Japanese population

A rapid and simple disc electrophoretic technique for the determination of saliva esterase (Set) types is described. The frequency of Set types was F 16.4%, FS 49.8% and S 33.8%. The estimated gene frequency of Set-1F was 0.413 and of Set-1S was 0.587. An accurate determination of Set types was possible in 5--7 week-old saliva stains. This system may be useful in medicolegal applications.

Frequencies of salivary genetic marker systems in the Japanese population and their application to forensic medicine

Seven salivary polymorphic systems were studied using whole and parotid saliva from random Japanese individuals. The gene frequencies obtained were: Pa+ = 0.212, Pb1 = 1.000, Pb2 = 0, Pr1 = 0.763, Pr2 = 0.237, Db+ = 0.051, Pm+ = 0.409, Ph+ = 0.026 and Amy1v = 0.013, respectively. Based on these gene frequencies, the chances for exclusion of falsely alleged fathers were calculated. The chance of exclusion on the basis of five salivary polymorphic systems was 0.305. The combined chance of exclusion utilizing only blood, serum and red-cell enzyme polymorphic systems among the Japanese population was 0.919; however, by applying salivary polymorphic systems to the calculation, the total exclusion rose to 0.944.

A variant protein in human parotid saliva detected by SDS polyacrylamide gel electrophoresis and its inheritance

In 218 parotid saliva samples collected at random from a Japanese population, two phenotypes were observed by SDS polyacrylamide gel electrophoresis. Inheritance was controlled by a dominant allele at an autosomal locus. The frequencies of the genes determining these phenotypes were for the Japanese population studied: Ph+ = 0.026 +/- 0.008, Ph- = 0.974 +/- 0.008.

Genetic protein polymorphisms in human saliva: an interpretive review

The purpose of this review is to summarize recent progress in the field of genetic protein polymorphisms found in human saliva since 1972. Prior to 1972 most of the investigations were related to amylase. The genetics of salivary amylase will not be considered here, since it has recently been thoroughly reviewed elsewhere (Merritt and Karn, 1977). In this review, special attention will be devoted to the complex interrelationships of the proline-rich (Pr), double-band (Db), acidic protein (Pa), and peroxidase (SAPX) systems. The biochemically related Pr, Db, and Pa systems show distinctive genetic patterns, and there are associations between the phenotypes indicating linkage relationships. There is also evidence for probable interaction of products of the Pa and SAPX loci. Electrophoretic properties of these proteins can be defined in several gel systems, permitting an accurate definition of phenotypes. The usefulness and limitations of the different gel systems in the interpretation of these electrophoretic patterns will be illustrated. Allelic frequencies of the systems to be discussed are given in Table I. To aid comprehension, the systems will be discussed in logical rather than historical sequence.

Isolation and partial characterization of human parotid basic proteins

Methods are presented for the isolation of basic proteins (Pb proteins) from human parotid saliva collected from humans possessing different alleles at the Pb locus. The proteins were found to be extremely basic, with an isoelectric point above 9.5. They contain approximately 45% of the basic amino acids histidine, lysine, and arginine, and are devoid of cysteine, proline, threonine, valine, methionine, and tryptophan. They are free of carbohydrate. A comparison of the amino acid sequence data of Pb protein to all available amino acid sequences revealed that no sequence similarities exist between the Pb proteins and any other proteins reported, although proteins of similar amino acid compositions have been reported by others. A model is presented with accounts for the several forms of allelic proteins based on observed amino acid sequence differences.

Human Pb, human post-Pb, and nonhuman primate Pb proteins: immunological and biochemical relationships

The isolation and characterization of a protein from human parotid saliva termed the "post-Pb protein" is described. By several criteria, this protein is closely related to the human Pb proteins. When reacted against antisera to human Pb protein in double diffusion, the post-Pb protein is found to be related to the Pb proteins by lines of identity. However, when the partial N-terminal amino acid sequences of the post-Pb protein and Pb proteins are compare, the sequences are not identical. Because of the similarity in size of the Pb and post-Pb proteins and because of the observed sequence differences, any product-precursor relationship between the Pb and post-Pb proteins is unlikely. The post-Pb protein probably is the product of a genetic locus different from the Pb locus. Two additional species of nonhuman primates (Papio papio and P. sphinx) have been found to have Pb proteins electrophoretically similar to these found in the rhesus monkey and differing from those in the human. The isolated Pb proteins of the rhesus monkey have been found to have close biochemical and immunological relationships to the human Pb proteins.

Polyacrylamide gel electrophoresis of human salivary histidine-rich-polypeptides

A method of polyacrylamide gel electrophoresis for examining histidine-rich-polypeptides in human saliva is described. Comparison is made to several commonly used electrophoretic techniques. The described method allows for the resolution of seven histidine-rich-polypeptide fractions and is convenient and quite reproducible.

New Genetic marker in human parotid saliva (pm)

In 195 parotid saliva samples collected at random from a Japanese population, two phenotypes were observed by electrophoresis in acid-urea starch gels. The protein showing polymorphisms was detected in the middle zone between Pa and Pb, and was tentatively designated Pm. Inheritance was controlled by a dominant allele at an autosomal locus. The frequencies of the genes determining these phenotypes were, for the Japanese population studied, Pm+=.38+/-.03, Pm-=.62+/-.03.

Salivary peroxidase (SAPX): genetic modification and relationship to the proline-rich (Pr) and acidic (Pa) proteins

There is genetic polymorphism of the peroxidase of human saliva, but not of leukocytes. The phenotypes are determined by autosomal inheritance, the phenotype of fast mobility (SAPX 1) being determined by homozygosity for a recessive gene (SAPX1) and the phenotypes of slow mobility (SAPX 2 and SAPX 3) being determined by two different genes, SAPX2 and SAPX3, with completely dominant expression at the same locus. The phenotypes are modified by varying degrees of endogenous proteolysis. The SAPX 2 and SAPX 3 types appear to be genetically controlled modifications of SAPX 1 rather than different primary gene products, because of their completely dominant inheritance, their larger molecular size compared to SAPX 1, and their dissociation with 2-mercaptoethanol to give SAPX 1. The acidic protein type Pa 1 is always found in association with SAPX 2, and an uncommon variant type Pa 2 is associated with SAPX 3. The most likely hypothesis is that the genes Pa1 and Pa2 produce products which modify the SAPX 1 type. When the Pa type is Pa 0, the SAPX phenotype is SAPX 1. Since 2-mercaptoethanol can dissociate the Pa 1 protein into a probable monomeric form, and can dissociate SAPX 2 and SAPX 3 to give SAPX 1, it is probable that Pa 1 and Pa 2 monomers complex with SAPX 1 through disulfide bonds to give SAPX 2 or SAPX 3 types. The frequencies of the genes determining the SAPX types are the same as those for Pa: SAPX1 and Pa0 = 0.787, SAPX2 and Pa1 = 0.208, SAPX3 and Pa2 = 0.005.

Genetic polymorphism of human anodal tear protein

Electrophoresis of human tears on slab polyacrylamide gels showed five phenotypes among anodal tear proteins. These phenotypes are the expression of autosomal codominant alleles. Gene frequencies are as follows: for Caucasians, At1 = 0.99, At3 = 0.01; for Negroes, At1 = 0.97, At2 = 0.03; for Chinese, At1 = 0.98, and At4 and At5 are both approximately 0.008.

The identification of a peptide in human parotid saliva particularly active in enhancing the glycolytic activity of the salivary micro-organisms

A factor in saliva responsible for markedly activating the glycolytic activity of micro-organisms was isolated from parotid secretions and identified as a small basic peptide. Analysis of the peptide showed a high proportion of histidine, lysine and arginine. Its minimum molecular weight was calculated to be between 2500 and 3000.

Genetic polymorphism of proline-rich human salivary proteins

In randomly collected saliva samples from 120 Caucasians, 79 Blacks, and 40 Chinese, three phenotypes were observed by electrophoresis in alkaline slab polyacrylamide gels. The proteins showing polymorphism were identical with four previously characterized proline-rich proteins. Inheritance is controlled by two autosomal codominant alleles. The gene frequencies were for Caucasians, Pr(l)=0.73, Pr(2)=0.27; for Blacks, Pr(1)=0.80, Pr(2)=0.20; for Chinese, Pr(l)=0.84, Pr(2)=0.16.