Structure and chromosomal localization of the human renal kallikrein gene

A regulatory mechanism of mouse kallikrein 1 gene expression by estrogen

Tissue kallikrein 1 (Klk1) is a serine protease that degrades several proteins including insulin-like growth factor binding protein-3 and extracellular matrix molecules. Klk1 mRNA expression in the mouse uterus was increased by estradiol-17β (E2). The present study aimed to clarify the regulatory mechanism for Klk1 expression by estrogen. The promoter analysis of the 5'-flanking region of Klk1 showed that the minimal promoter of Klk1 existed in the -136/+24 region, and the estrogen-responsive region in the -433/-136 region. Tamoxifen increased Klk1 mRNA expression and the promoter activity, suggesting the involvement of AP-1 sites. Site-directed mutagenesis for the putative AP-1 sites in the -433/-136 region showed that the two putative AP-1 sites were involved in the regulation of Klk1 expression. Binding of estrogen receptor α (ERα) to the -433/-136 region was revealed by Chip assay. These results indicated that ERα bound the two putative AP-1 sites and transactivated Klk1 in the mouse uterus.

A positive association between the human tissue kallikerin gene A2233C polymorphism and blood pressure response to benazepril

BACKGROUND

It is generally believed that essential hypertension is influenced by both genetic and environmental factors, as well as their interactions. Tissue kallikrein encoded by the tissue kallikrein gene (KLK1) is a key serine proteinase of kallikrein-kinin system, which is capable of generating potent vasactive peptides, kinins, by selective cleavage of the kininogen substrate. It was reported that the A2233 → C polymorphism in KLK1 gene is associated with essential hypertension. The aim of this study was to examine whether the molecular variations of KLK1 play role in determining the therapeutic response to benazepril, an ACE inhibitor.

METHODS

A total of 331 hypertensive individuals were recruited and treated with benazepril for 15 days. A variant impact of KLK1 A2233C was revealed. Chi-square analysis showed that the hypertensive subjects with the mutation genotype (AC + CC) had a higher proportion in systolic blood pressure (SBP, 88.1% vs. 79.0%, χ² = 4.141, p = 0.042) and diastolic blood pressure (DBP, 91.1% vs. 79.2%, χ² = 9.336, p = 0.002), respectively, to benazepril medication in good responders than in poor responders. Logistic regression analysis indicated that the hypertensive subjects with AC + CC genotype were more sensitive to the benazepril therapy in SBP (OR=1.97, 95% CI: 1.02-3.80, p = 0.044) and DBP (OR = 1.91, 95% CI: 2.69-5.16, p = 0.003), as compared with those hypertensive subjects with AA genotype.

CONCLUSION

Our findings suggest that the A2233C polymorphism of KLK1 may be a marker of evaluation of hypertensive subjects' responses to angiotensin I converting enzyme inhibitors benazepril.

A single nucleotide polymorphism in exon 3 of the kallikrein 1 gene is associated with large but not small abdominal aortic aneurysm

OBJECTIVE

Abdominal aortic aneurysm (AAA) is a late onset degenerative condition with an inherited component thought to be due to multiple risk alleles. A locus on chromosomes 19q13 has been previously associated with AAA. The gene encoding kallikrein 1 (KLK1) is located on chromosome 19q13 and the single nucleotide polymorphism (SNP) rs5516 has been previously shown to lead to structural changes in the KLK1 transcription regulatory region. The aim of this study was to investigate whether rs5516 was associated with AAA and aortic diameter.

METHODS

We performed a case-control study on two independent subject groups from Western Australia (n=1304) and Queensland (n=325) of which 609 and 225 had an AAA, respectively. In addition, we analysed RNA extracted from abdominal aortic biopsies from 12 patients undergoing AAA surgery and 6 organ donors.

RESULTS

After adjusting for other risk factors the G allele of the rs5516 polymorphism was associated with large but not small AAA using a dominant model in the Western Australian men and a recessive model in Queensland subjects. In subjects with large AAA the G allele was associated with aortic diameter. The short splice variant of KLK1 was upregulated within AAA compared to control biopsies.

CONCLUSION

This study suggests that a genetic polymorphism in KLK1 may contribute to the risk of developing later stage AAA.

Prognostic value and biological role of the kallikrein-related peptidases in human malignancies

Cancer is a substantial health problem for the populations of the Western world. The discovery of new molecular biomarkers for diagnosis, prognosis and monitoring patients' response to therapy can aid in combating this complicated disease. The human kallikrein-related peptidases (human tissue kallikreins [KLKs]) are encoded by a continuous multigene family, located on chromosomal region 19q13.3-4. KLK3 (prostate-specific antigen) is the most efficient cancer biomarker ever employed. KLK genes are expressed abnormally in various malignancies, where they affect cancer-cell growth and metastasis. Their deregulated expression pattern, often associated with various clinicopathological characteristics of cancer patients, can be exploited, solely or within multiparametric panels, as a prognostic biomarker. Recent data illustrate that discernible molecular modulations of KLKs, occurring as a result of cancer cells' treatment with antitumor agents, may serve as new potential biomarkers, possibly predicting patients' treatment response. It is believed that KLKs might be employed in future clinical practice as novel and effective tumor markers.

TATA box polymorphisms in human gene promoters and associated hereditary pathologies

TATA-binding protein (TBP) is the first basal factor that recognizes and binds a TATA box on TATA-containing gene promoters transcribed by RNA polymerase II. Data available in the literature are indicative of admissible variability of the TATA box. The TATA box flanking sequences can influence TBP affinity as well as the level of basal and activated transcription. The possibility of mediated involvement in in vivo gene expression regulation of the TBP interactions with variant TATA boxes is supported by data on TATA box polymorphisms and associated human hereditary pathologies. A table containing data on TATA element polymorphisms in human gene promoters (about 40 mutations have been described), associated with particular pathologies, their short functional characteristics, and manifestation mechanisms of TATA-box SNPs is presented. Four classes of polymorphisms are considered: TATA box polymorphisms that weaken and enhance promoter, polymorphisms causing TATA box emergence and disappearance, and human virus TATA box polymorphisms. The described examples are indicative of the polymorphism-associated severe pathologies like thalassemia, the increased risk of hepatocellular carcinoma, sensitivity to H. pylori infection, oral cavity and lung cancers, arterial hypertension, etc.

Kallikreins and lupus nephritis

The kidney kallikrein-kinin system plays important roles in inflammation, coagulation, angiogenesis, and regulation of vessel tone and permeability. In this issue of the JCI, Liu et al. provide data that suggest a protective role for kallikrein in animal models of anti-glomerular basement membrane(GBM) antibody-induced nephritis, an experimental model of Goodpasture disease (see the related article beginning on page 911). Furthermore, human systemic lupus erythematosus and lupus nephritis were shown to be associated with kallikrein 1 (KLK1) and the KLK3 promoter. The authors suggest that kallikrein genes are involved in the development of SLE and lupus nephritis and may exert a renoprotective role. It is possible, however, that the kallikrein-kinin system may play dual roles: protecting the kidney against ischemia and interstitial fibrosis while also mediating vasodilation, inflammation, and activation of the innate immune response.

The Tissue Kallikrein Family of Serine Proteases: Functional Roles in Human Disease and Potential as Clinical Biomarkers

Prostate specific antigen (PSA) or human kallikrein 3 (hK3) has long been an effective biomarker for prostate cancer. Now, other members of the tissue kallikrein (KLK) gene family are fast becoming of clinical interest due to their potential as prognostic biomarkers. particularly for hormone dependent cancers. The tissue kallikreins are serine proteases that are encoded by highly conserved multi-gene family clusters in rodents and humans. The rat and mouse loci contain 10 and 25 functional genes, respectively, while the human locus at 19q 13.4 contains 15 genes. The structural organization and size of these genes are similar across species; all genes have 5 coding exons that encode a prepro-enzyme. Although the physiological activators of these zymogens have not been described, in vitro biochemical studies show that some kallikreins can auto-activate and others can activate each other, suggesting that the kallikreins may participate in an enzymatic cascade similar to that of the coagulation cascade. These genes are expressed, to varying degrees, in a wide range of tissues suggesting a functional involvement in a diverse range of physiological and pathophysiological processes. These include roles in normal skin desquamation and psoriatic lesions, tooth development, neural plasticity, and Alzheimer's disease (AD). Of particular interest is the expression of many kallikreins in prostate, ovarian, and breast cancers where they are emerging as useful prognostic indicators of disease progression.

A coding polymorphism of the kallikrein 1 gene is associated with essential hypertension: a tagging SNP-based association study in a Chinese Han population

OBJECTIVE

The aim of this study was to investigate the association between common variants in the human tissue kallikrein 1 (KLK1) gene and susceptibility to essential hypertension in Chinese Han.

METHODS

A tagging single nucleotide polymorphism (tSNP) approach was used for a case-control study in 2411 patients with essential hypertension and 2348 controls. All DNA samples and clinical data were collected from the International Collaborative Study of Cardiovascular Disease in Asia (InterASIA).

RESULTS

Based on the HapMap data of Han Chinese in Beijing (CHB) population, two non-synonymous polymorphisms, namely rs5517 (Glu162Lys) and rs5516 (Gln121Glu), were selected as tSNPs which could efficiently tag eight SNPs of the KLK1 gene with R larger than 90% for both haplotypes and single locus. Significant differences were found between groups for frequencies of rs5517 A allele (42.48% in cases versus 39.32% in controls, P=0.0019) and AA genotype [adjusted odds ratio (OR)=1.25 for AA versus AG/GG, P=0.0067]. The haplotype composed of the rs5517 A and rs5516 G allele significantly increased the risk of hypertension, with adjusted OR of 1.12 [95% confidence interval (CI), 1.04-1.28, P=0.0377] when compared with the common haplotype G-C. Diplotype analysis also showed a significant association between the diplotype of AG-AC and essential hypertension (OR=1.34, 95% CI, 1.07-1.68, P=0.0096).

CONCLUSIONS

The present study suggested that rs5517 in the KLK1 gene was significantly associated with essential hypertension in a Chinese Han population.

The epigenetic basis for the aberrant expression of kallikreins in human cancers

The tissue kallikrein gene family consists of 15 genes tandemly arranged on human chromosome 19q13.4. Most kallikrein genes are characterized by aberrant expression patterns in various human cancers, a feature that makes them ideal cancer biomarkers. In the present study, we investigated the effect of the epigenetic drug compound 5-aza-2'-deoxycytidine on the expression of downregulated kallikrein genes in prostate, breast, and ovarian cancer cell lines. Reactivation of multiple kallikrein genes was observed, although some of these genes do not contain CpG islands in their genomic sequence. Epigenetic regulation provides a new mechanism for the pharmacological modulation of kallikreins in human cancers with putative therapeutic implications.

Capillary electrophoresis for the investigation of prostate-specific antigen heterogeneity

Prostate-specific antigen (PSA) is a single-chain glycoprotein that is used as a biomarker for prostate-related diseases. PSA has one known posttranslational modification, a sialylated diantennary N-linked oligosaccharide attached to the asparagine residue N45. In this study capillary electrophoresis (CE) was employed to separate the isoforms of seven commercially available free PSA samples, two of which were specialized: enzymatically active PSA and noncomplexing PSA. The free PSA samples examined migrated as four to nine distinct, highly resolved peaks, indicating the presence of several isoforms differing in their oligosaccharide compositions. Overall, the use of CE provides a rapid, reproducible method for separation of PSA into its individual isoforms.

Serine proteases and cardiac function

The serine proteases of the trypsin superfamily are versatile enzymes involved in a variety of biological processes. In the cardiovascular system, the importance of these enzymes in blood coagulation, platelet activation, fibrinolysis, and thrombosis has been well established. Recent studies have shown that trypin-like serine proteases are also important in maintaining cardiac function and contribute to heart-related disease processes. In this review, we describe the biological function of corin, tissue kallikrein, chymase and urokinase and discuss their roles in cardiovascular diseases such as hypertension, cardiac hypertrophy, heart failure, and aneurysm.

Relationship between the regulatory region polymorphism of human tissue kallikrein gene and essential hypertension

Ten alleles with length and nucleotide sequence variations were identified in the regulatory region of human tissue kallikrein gene. This present study aimed to study the polymorphisms of the regulatory region of human tissue kallikrein gene of the Chinese and investigate the relationship of the polymorphisms with essential hypertension. A case-control study was conducted in 200 hypertensive and 200 normotensive subjects of unrelated Chinese Han origin. All subjects were aged from 30 to 70 years and had no history of diabetes mellitus, kidney failure, or thyroid gland disease. The alleles were detected by polymerase chain reaction (PCR) and genotyping was performed with allele-specific oligonucleotide analysis (ASO). Data from the essential hypertensive and control subjects were statistically analysed by the Student's t-test and chi2-test. The age- and gender-matching of the groups were accurate. The case group and the control group were in Hardy-Weinberg equilibrium at this locus (cases, P=0.313; control subjects, P=0.457). There were nine alleles among the case and control groups, and the allele frequencies were found to be significantly different between cases and controls (chi2=25.701, P<0.001). The genotype frequencies were also significantly different (chi2=70.100, P<0.001) between these two groups. In conclusion, there are polymorphisms in the regulatory region of human tissue kallikrein gene in the Chinese Han people. Differences in both allele frequencies and genotype frequencies between these two groups have provided evidence towards the association of hypertension with the polymorphisms in this studied site.

Selective recognition of enzymatically active prostate-specific antigen (PSA) by anti-PSA monoclonal antibodies

Prostate-specific antigen (PSA) is widely used as a serum marker for the diagnosis of prostate cancer. To evaluate two anti-free PSA monoclonal antibodies (mAbs) as potential tools in new generations of more relevant PSA assays, we report here their properties towards the recognition of specific forms of free PSA in seminal fluids, LNCaP supernatants, 'non-binding' PSA and sera from cancer patients. PSA from these different origins was immunopurified by the two anti-free PSA mAbs (5D3D11 and 6C8D8) as well as by an anti-total PSA mAb. The composition of the different immunopurified PSA fractions was analysed and their respective enzymatic activities were determined. In seminal fluid, enzymatically active PSA was equally purified with the three mAbs. In LNCaP supernatants and human sera, 5D3D11 immunopurified active PSA mainly, whereas 6C8D8 immunopurified PSA with residual activity. In sera of prostate cancer patients, we identified the presence of a mature inactive PSA form which can be activated into active PSA by use of high saline concentration or capture by an anti-total PSA mAb capable of enhancing PSA activity. According to PSA models built by comparative modelling with the crystal structure of horse prostate kallikrein described previously, we assume that active and activable PSA could correspond to mature intact PSA with open and closed conformations of the kallikrein loop. The specificity of 5D3D11 was restricted to both active and activable PSA, whereas 6C8D8 recognized all free PSA including intact PSA, proforms and internally cleaved PSA.

Human Tissue Kallikreins: Physiologic Roles and Applications in Cancer

Tissue kallikreins are members of the S1 family (clan SA) of trypsin-like serine proteases and are present in at least six mammalian orders. In humans, tissue kallikreins (hK) are encoded by 15 structurally similar, steroid hormone–regulated genes (KLK) that colocalize to chromosome 19q13.4, representing the largest cluster of contiguous protease genes in the entire genome. hKs are widely expressed in diverse tissues and implicated in a range of normal physiologic functions from the regulation of blood pressure and electrolyte balance to tissue remodeling, prohormone processing, neural plasticity, and skin desquamation. Several lines of evidence suggest that hKs may be involved in cascade reactions and that cross-talk may exist with proteases of other catalytic classes. The proteolytic activity of hKs is regulated in several ways including zymogen activation, endogenous inhibitors, such as serpins, and via internal (auto)cleavage leading to inactivation. Dysregulated hK expression is associated with multiple diseases, primarily cancer. As a consequence, many kallikreins, in addition to hK3/PSA, have been identified as promising diagnostic and/or prognostic biomarkers for several cancer types, including ovarian, breast, and prostate. Recent data also suggest that hKs may be causally involved in carcinogenesis, particularly in tumor metastasis and invasion, and, thus, may represent attractive drug targets to consider for therapeutic intervention.

An overview of the kallikrein gene families in humans and other species: emerging candidate tumour markers

Kallikreins are serine proteases with diverse physiologic functions. They are represented by multigene families in many animal species, especially in rat and mouse. Recently, the human kallikrein gene family has been fully characterized and includes 15 members, tandemly localized on chromosome 19q13.4. A new definition has now been proposed for kallikreins, which is not based on function but, rather, on close proximity and structural similarities. In this review, we summarize available information about kallikreins in many animal species with special emphasis on human kallikreins. We discuss the common structural features of kallikreins at the DNA, mRNA and protein levels and overview their evolutionary history. Kallikreins are expressed in a wide range of tissues including the salivary gland, endocrine or endocrine-related tissues such as testis, prostate, breast and endometrium and in the central nervous system. Most, if not all, genes are under steroid hormone regulation. Accumulating evidence indicates that kallikreins are involved in many pathologic conditions. Of special interest is the potential role of kallikreins in the central nervous system. In addition, many kallikreins seem to be candidate tumor markers for many malignancies, especially those of endocrine-related organs.

Molecular communication between androgen receptor and general transcription machinery

The androgen-androgen receptor (AR) signaling pathway plays a key role in proper development and function of male reproductive organs. Like other transcriptional regulators, AR may communicate with the general transcription machinery on the core promoter to exert its function as a transcriptional modulator. The molecular communication between AR and the general transcription machinery may be achieved either by the direct protein-protein interaction between AR and the general transcription machinery or by the indirect interaction mediated by coregulators. Analyses of AR-mediated transcription suggest that the orchestrated interaction of AR with the transcription factors IIF (TFIIF) and IIH (TFIIH), and positive transcription elongation factor b (P-TEFb), may increase efficiency of transcriptional elongation from the androgen target genes, such as prostate specific antigen (PSA). Based on studies so far, AR may regulate transcription not by enhanced assembly of preinitiation transcription complex but by regulating promoter clearance and elongation stage of transcription.

Visualization of the sequential changes in immunolabelled tissue kininogenase which accompany follicular development and luteinization of angiogenic granulosa cells of the ovary

The serine protease, tissue kininogenase (kallikrein), belongs to a unique family of enzymes that cleaves the decapeptide, kallidin, from the endogenous substrate kininogen. By analysis of genealogy patterns, rat KLK gene family members have been detected in ovarian luteinizing granulosa cells of both gonadotrophin-treated and nontreated control rats. Preliminary experiments suggest that when granulosa and endothelial cells are co-cultured, granulosa cells participate in the formation of vascular capillary tubes. This inherent capacity of granulosa cells to behave and respond like endothelial cells may be of importance in the aetiology of ovarian angiogenesis, which drives new blood vessel formation in the ovary. Recently, we demonstrated that tissue kininogenase showed intense immunolabelling in angiogenic endothelial cells isolated from bovine mature and regressing corpora lutea. Therefore, the question to answer was whether granulosa cells possess the same capacity to express the kallikrein-kinin cascade as do microvascular endothelial cells. As a first step, experiments were designed to determine the expression and visualization of tissue kininogenase (both active and pro-forms) as well as kininogen and kinin receptors in granulosa cells of different developmental stage and segments of the ovarian follicle by immunoperoxidase, fluorescent microscopy (confocal) and in situ hybridization.

Organization and evolution of the glandular kallikrein locus in Mus musculus

The gene of tissue kallikrein and closely related genes constitute the glandular kallikrein (GK) gene family. The number of members varies between species, ranging from three human to 25 murine. Recently, the gene family was extended with 12 new members, KLK4-KLK15, that were identified adjacent to the classical GK genes on human chromosome 19. In this report, the structure and phylogeny of the mouse GK gene locus are described. A comparison of the human and murine loci shows that the locations of the tissue kallikrein gene and KLK4-KLK15 are conserved. The region between the tissue kallikrein gene and KLK15, devoid of genes in human, is expanded and contains 23 classical GK genes in mouse. Downstream of KLK15, where the genes encoding PSA and hK2 are located in human, mouse carries the pseudogene PsimGK25. Phylogenetic analyses show that classical GK genes emerged after the separation of the primate and rodent lineages, forming a subgroup within the newly extended GK family.

The structure of human prokallikrein 6 reveals a novel activation mechanism for the kallikrein family

Zyme/protease M/neurosin/human kallikrein 6 (hK6) is a member of the human kallikrein family of trypsin-like serine proteinases and was originally identified as being down-regulated in metastatic breast and ovarian tumors when compared with corresponding primary tumors. Recent evidence suggests that hK6 may serve as a circulating tumor marker in ovarian cancers. In addition, it was described in the brain of Parkinson's disease and Alzheimer's disease patients, where it is implicated in amyloid precursor protein processing. It is thus a biomarker for these diseases. To examine the mechanism of activation of hK6, we have solved the structure of its proform, the first of a human kallikrein family member. The proenzyme displays a fold that exhibits chimeric features between those of trypsinogen and other family members. It lacks the characteristic "kallikrein loop" and forms the six disulfide bridges of trypsin. Pro-hK6 displays a completely closed specificity pocket and a unique conformation of the regions involved in structural rearrangements upon proteolytic cleavage activation. This points to a novel activation mechanism, which could be extrapolated to other human kallikreins.

Human tissue kallikreins: a new enzymatic cascade pathway?

Serine proteases are proteolytic enzymes with an active serine residue in their catalytic site. Kallikreins are a subgroup of the serine protease family which is known to have diverse physiological functions. The human kallikrein gene family has now been fully characterized and includes 15 members tandemly located on chromosome 19q13.4. Here we discuss the common structural features of kallikreins at the DNA, mRNA and protein levels and summarize their tissue expression and hormonal regulation patterns. Kallikreins are expressed in many tissues including the salivary gland, endocrine tissues such as testis, prostate, breast and endometrium, and in the central nervous system. Most genes appear to be under steroid hormone regulation. The occurrence of several splice variants is common among kallikreins, and some of the splice variants seem to be tissue-specific and might be related to certain pathological conditions. Kallikreins are secreted in an inactive 'zymogen' form which is activated by cleavage of an N-terminal peptide. Some kalikreins can undergo autoactivation while others may be activated by other kallikreins or other proteases. Most kallikreins are predicted to have trypsin-like enzymatic activity except three which are probably chymotrypsin-like. New, but mainly circumstantial evidence, suggests that at least some kallikreins may be part of a novel enzymatic cascade pathway which is turned-on in aggressive forms of ovarian and probably other cancers.

Kallikrein cascade and cytokines in inflamed joints

Rheumatoid arthritis is a chronic multi-system disease of unknown aetiology. The current hypothesis is that an unknown antigen triggers an autoimmune response in a genetically susceptible individual. The predominant pathological change is that of an inflammatory synovitis, characterised by cellular infiltrates and angiogenesis, with subsequent bone and cartilage destruction. These pathological changes are as a result of the activation of a variety of cells, inflammatory mediators, and effector molecules. The pro-inflammatory kinins and cytokines appear to play a central role in the pathogenesis of rheumatoid arthritis. Sufficient evidence exists that establishes a key role for the kallikrein-kinin cascade in inflamed joints. In addition, there appears to be an inter-relationship between cytokines and kinins in the inflammatory process. Kinins induce the release of cytokines, and cytokines have been shown to augment the effects of kinins. This may lead to an enhancement and perpetuation of the inflammatory process. In this review, we report a first study, correlating markers of disease with the kallikrein-kinin cascade and with cytokines.

Loss-of-function polymorphism of the human kallikrein gene with reduced urinary kallikrein activity

Kallikrein is synthesized in the distal tubules and produces kinins, which are involved in the regulation of vascular tone in the kidney. Urinary kallikrein activity has been reported to be partly inherited and to be reduced in essential hypertension. In a systematic search for molecular variants of the human kallikrein gene, nine single-nucleotide polymorphisms were identified. Five of those polymorphisms, including two nonsynonymous substitutions in exon 3, i.e., Arg53His (allelic frequency in Caucasian subjects, 0.03) and Gln121Glu (allelic frequency, 0.33), were studied in a normotensive group and two independent hypertensive groups for which 24-h urinary kallikrein activity had been measured. A significant decrease in urinary kallikrein activity was observed for the subjects who were heterozygous for the Arg53His polymorphism, compared with the other subjects. This finding was consistent in the two hypertensive groups and was observed with several kallikrein enzymatic assays. The Gln121Glu polymorphism and the other polymorphisms were not associated with changes in urinary kallikrein activity. None of the polymorphisms was associated with hypertension. Recombinant kallikrein variants were synthesized and enzymatically characterized, using native kininogen and kininogen-derived synthetic peptide substrates. No important effect was observed after Gln121 mutation, but there was a major decrease in enzyme activity when Arg53 was replaced by histidine. A model of kallikrein derived from crystallographic data suggested that Arg53 can affect substrate binding. The identification of a subset of subjects with genetically reduced kallikrein activity as a result of an amino acid mutation could facilitate analysis of the role of the kallikrein-kinin system in renal and vascular diseases.

Association of the tissue kallikrein gene promoter with ESRD and hypertension

BACKGROUND

Kallikreins have long been implicated in human essential hypertension and associated complications. In particular, low urinary kallikrein excretion has been associated with hypertension and renal disease in African Americans. In an effort to identify the source of differential kallikrein excretion, we investigated the promoter of KLK1, the tissue kallikrein gene. The KLK1 promoter is uniquely polymorphic with a poly-G length polymorphism coupled with multiple single base substitutions. In this report, we genetically evaluated the association of KLK1 gene promoter alleles with end-stage renal disease (ESRD) in African Americans.

METHODS

A total of 15 haplotypes were identified in the KLK1 promoter region through detailed DNA sequence analysis. This polymorphic region was then genetically evaluated for association with ESRD in African Americans with diabetic and non-diabetic etiologies of ESRD.

RESULTS

The complex polymorphic nature of the promoter presents challenges to determining the alleles. We have redefined the region as six separate loci: five substitution loci and one length locus. The length locus was defined as G repeats starting at position -130 and ending at -121 on the gene. Among four relevant substitution loci for this study, one at position -131, just outside the G repeats, is an A-to-G substitution. The other three variant positions are -129, -128, and -127, all G-to-C substitutions within the G repeats. This region was genotyped in African American subjects with and without ESRD using semiautomated sequencing. Four different G repeat alleles ranging from 11.8% for 12 Gs to 52.3% for 10 Gs were observed in 86 control subjects. The C substitution of Gs ranges from 2.9% at position -127 to 8.2% at -129. When affected probands from each of 76 hypertensive ESRD families were genotyped, an association for the 12 G allele, the longest of the length locus alleles, was detected (allele specific P = 0.004 and locus total P = 0.02). When all ESRD affected individuals with hypertension from each family (107 patients in total) were used in the analysis, an even stronger association was observed for this allele (allele specific P = 0.003, locus total P = 0.01). This allele was more frequent in the hypertensive (non-diabetic) patients (0.20 in probands and 0.19 in all ESRD cases) than in the controls (0.12). No evidence of association in diabetic ESRD patients was observed (P = 0.93).

CONCLUSIONS

The KLK1 promoter is uniquely polymorphic. The observed genetic association suggests an etiologic effect of the KLK1 promoter on hypertension and/or hypertension associated ESRD.

Involvement of the C-terminal end of the prostrate-specific antigen in a conformational epitope: characterization by proteolytic degradation of monoclonal antibody-bound antigen and mass spectrometry

Prostate-specific antigen (PSA), a 237-amino acid glycoprotein, encoded by the hKLK3 gene, is widely used as a serum marker for the diagnosis and management of prostate cancer. We report here the localization of a conformational epitope recognized by the anti-total PSA monoclonal antibody (mAb) 11E5C6, by proteolytic degradation of mAb-bound antigen followed by mass spectrometric analyses of the peptides generated. These two technologies, combined with molecular display, allowed the identification of amino acid residues contained within three different peptides distant on the PSA sequence, but close in the PSA three-dimensional structure, that may be part of the mAb 11E5C6 epitope. The last four C-terminal amino acid residues are included in this epitope, as well as certain other C-terminal residues between Y225 and T232. The involvement of the PSA C-terminal end in the mAb 11E5C6 epitope was confirmed by western blotting experiments with the recombinant protein proPSA-RP1, resulting from the cloning of an alternative transcript of the hKLK3 gene, in which the PSA C-terminal end was deleted and replaced by another sequence. Although the anti-total PSA mAb 5D5A5 used as a control bound proPSA-RP1, mAb 11E5C6 did not. The requirement of the C-terminal end for the recognition by mAb 11E5C6 may be useful for the discrimination of PSA-related forms.

The new human tissue kallikrein gene family: structure, function, and association to disease

The human tissue kallikrein gene family was, until recently, thought to consist of only three genes. Two of these human kallikreins, prostate-specific antigen and human glandular kallikrein 2, are currently used as valuable biomarkers of prostatic carcinoma. More recently, new kallikrein-like genes have been discovered. It is now clear that the human tissue kallikrein gene family contains at least 15 genes. All genes share important similarities, including mapping at the same chromosomal locus (19q13.4), significant homology at both the nucleotide and protein level, and similar genomic organization. All genes encode for putative serine proteases and most of them are regulated by steroid hormones. Recent data suggest that at least a few of these kallikrein genes are connected to malignancy. In this review, we summarize the recently accumulated knowledge on the human tissue kallikrein gene family, including gene and protein structure, predicted enzymatic activities, tissue expression, hormonal regulation, and alternative splicing. We further describe the reported associations of the human kallikreins with various human diseases and identify future avenues for research.

The expanded human kallikrein (KLK) gene family: genomic organisation, tissue-specific expression and potential functions

The tissue kallikreins are serine proteases encoded by highly conserved multi-gene families. The rodent kallikrein (KLK) families are particularly large, consisting of 13-26 genes clustered in one chromosomal locus. It has been recently recognised that the human KLK gene family is of a similar size (15 genes) with the identification of another 12 related genes (KLK4-KLK15) within and adjacent to the original human KLK locus (KLK1-3) on chromosome 19q13.4. The structural organisation and size of these new genes is similar to that of other KLK genes except for additional exons encoding 5' or 3' untranslated regions. Moreover, many of these genes have multiple mRNA transcripts, a trait not observed with rodent genes. Unlike all other kallikreins, the KLK4-KLK15 encoded proteases are less related (25-44%) and do not contain a conventional kallikrein loop. Clusters of genes exhibit high prostatic (KLK2-4, KLK15) or pancreatic (KLK6-13) expression, suggesting evolutionary conservation of elements conferring tissue specificity. These genes are also expressed, to varying degrees, in a wider range of tissues suggesting a functional involvement of these newer human kallikrein proteases in a diverse range of physiological processes.

Detection of tissue kallikrein and kinin B1 and B2 receptor mRNAs in human brain by in situ RT-PCR

Tissue kallikrein (TK) and kinin receptors have been immuno-localized in various areas of the human nervous system, suggesting that the kallikrein-kinin system (KKS) may be functionally active in the brain. The aim of this study was to determine the cellular expression of TK and kinin B1 and B2 receptor mRNAs in specific regions of the human brain by in situ reverse transcriptase polymerase chain reaction. Autopsy samples of the brain, spinal cord, kidney and salivary gland were embedded in paraffin. Sections (5 microm), adhered onto silane coated glass slides, were treated with Proteinase K and DNase, followed by reverse transcription polymerase chain reaction with specific KKS primers and digoxigenin-dUTP. Detection of the digoxigenin-label demonstrated localization of TK, B1 and B2 mRNAs in the cytoplasm of some neuronal cell bodies in the hypothalamus, thalamus, frontal cortex and spinal cord. TK mRNA was also observed in the ependymal cells lining the cerebral ventricles and epithelial cells of the choroid plexus. In the choroid plexus, only B1 gene expression was observed in some choroidal epithelial cells while no B2 labeling was detected. The identification of mRNAs to TK, B1 and B2 kinin receptors in human nervous tissue supports previous evidence for the presence of the KKS in the brain and confirms localized protein synthesis.

Cloning and characterization of mouse klk27, a novel tissue kallikrein expressed in testicular Leydig cells and exhibiting chymotrypsin-like specificity

A cDNA clone of a new mouse tissue kallikrein, designated mKlk27, was isolated from an adult mouse testis cDNA library. mKlk27 was expressed in the submaxillary glands and testis of the mouse. In testis, mKlk27 gene was expressed exclusively in the Leydig cells of the adult mouse. Active recombinant mKlk27 exhibited chymotrypsin-like cleavage specificity. A single amino-acid substitution of Gly for Asp at position 209 in mKlk27 resulted in complete loss of its chymotryptic activity but acquisition of tryptic activity. mKlk27 effectively hydrolyzed casein, gelatin and fibronectin. Insulin-like growth factor binding protein-3 was also hydrolyzed by recombinant mKlk27. These results suggest that mKlk27 plays an important role in association with the function of the adult mouse testis.

Glandular kallikreins of the cotton-top tamarin: molecular cloning of the gene encoding the tissue kallikrein

The glandular kallikrein family is composed of structurally related serine proteases. Studies show that the mouse family encompasses at least 14 highly conserved functional genes, but of these only the tissue kallikarein has a human ortholog. In man, the tissue kallikrein display high sequence similarity with prostate specific antigen and human glandular kallikrein 2, suggesting that they evolved after the separation of primates and rodents. A phylogenetic study of the genes encoding glandular kallikreins in species evolutionarily located between rodents and man may reveal interesting details on how the gene family evolved, which in turn could yield information about the function of the proteins. Therefore, we have initiated a study of the glandular kallikreins of the cotton-top tamarin (Saguinus oedipus), a New World Monkey. Here, we report the cloning and nucleotide sequence of one of these, the tissue kallikrein gene. The gene of 4.4 kb is composed of five exons, and the structure is 90% similar to that of the orthologous human gene. It gives rise to a polypeptide of 261 amino acids, including a signal peptide of 17 residues, a pro-piece of 7 residues, and the mature protein of 237 residues with an estimated molecular mass of 26.3 kD. The similarity to the human prostate specific antigen and human glandular kallikrein 2 genes is 73% and 72%, respectively, including introns and flanking regions. The lower similarity to these genes compared with the human tissue kallikrein gene indicates that they, or a progenitor to them, arose in primates prior to the separation of New and Old World monkeys. Genomic Southern blots also show that the cotton-top tamarin genome encompasses at least one more glandular kallikrein gene.

KLK12 is a novel serine protease and a new member of the human kallikrein gene family-differential expression in breast cancer

Kallikreins are a subgroup of serine proteases that are involved in the posttranslational processing of polypeptide precursors. Growing evidence suggests that many kallikreins are implicated in carcinogenesis. In rodents, kallikreins are encoded by a large multigene family, but in humans, only three genes have been identified. By using the positional candidate approach, we were able to identify a new kallikrein-like gene, tentatively named KLK12 (for kallikrein gene 12). This new gene maps to chromosome 19q13.3-q13.4, is formed of five coding exons, and shows structural similarity to serine proteases and other known kallikreins. KLK12 is expressed in a variety of tissues including salivary gland, stomach, uterus, lung, thymus, prostate, colon, brain, breast, thyroid, and trachea. We identified three splicing forms of KLK12 that are expressed in many tissues. Our preliminary results indicate that the expression of KLK12 is down-regulated at the mRNA level in breast cancer tissues and is up-regulated by steroid hormones in breast and prostate cancer cell lines. This gene may be involved in the pathogenesis and/or progression of certain cancer types and may find applicability as a novel cancer biomarker.

Expression of prostate-specific antigen and human glandular kallikrein 2 in the thyroid gland

Prostate-specific antigen (PSA) and human glandular kallikrein 2 (hK2) are two closely related kallikreins, primarily produced by the prostate. These serine proteases are now used as biomarkers for the diagnosis and management of prostate cancer. Until recently, PSA and hK2 were thought to be strictly expressed in the prostate; however, numerous studies confirmed their presence in various biological fluids as well as in many normal and malignant tissues. Using reverse transcription-polymerase chain reaction (RT-PCR), we screened RNA extracted from 26 different normal tissues and found that both genes are expressed in the thyroid. Subsequently, we analyzed 15 RNAs extracted from thyroid tissues (10 benign and 5 malignant lesions) and found that both kallikreins were expressed in five specimens (four benign lesions and one malignant). Sequencing of the PCR products confirmed the specificity of our experiments. Immunohistochemistry localized PSA in oxyphilic cells of thyroid tissue. These data confirm expression of both PSA and hK2 in thyroid tissue and suggest that oxyphils are the source of their production. The function of these two proteases in thyroid tissue is unknown.

Genomic organization of the human kallikrein gene family on chromosome 19q13.3-q13.4

Kallikreins are a subgroup of serine proteases with diverse physiological functions. Recently, growing evidence indicates that many kallikrein genes are involved in malignancy. In rodents, kallikreins are encoded by a large multigene family, but in humans only three kallikreins were thought to exist. Based on the homology between the human and rodent kallikrein loci, we studied a 300 kb region of genomic sequences around the putative KLK1 gene locus on chromosome 19q13.3-q13.4. By using linear sequence information, restriction analysis, end sequencing, PCR and blotting techniques, as well as bioinformatic approaches, we were able to construct the first detailed map of the human kallikrein gene family. Comparative analysis of genes located in this area, provides strong evidence that the human kallikrein gene family locus on chromosome 19 is considerably larger than previously thought, containing at least fifteen genes. We have established, for the first time, the common structural features that apply to all members of the expanded kallikrein multigene family. Our map specifies the distance between genes to one base pair accuracy, the relative location, and the direction of transcription of all 15 genes. Determination of the true size of the kallikrein family in humans is important for our understanding of the contribution of the kallikreins to human biology and pathophysiology.

The molecular basis of hypertension

More than 50 million Americans display blood pressures outside the safe physiological range. Unfortunately for most individuals, the molecular basis of hypertension is unknown, in part because pathological elevations of blood pressure are the result of abnormal expression of multiple genes. This review identifies a number of important blood pressure regulatory genes including their loci in the human, mouse, and rat genome. Phenotypes of gene deletions and overexpression in mice are summarized. More detailed discussion of selected gene products follows, beginning with proteins involved in ion transport, specifically the epithelial sodium channel and sodium proton exchangers. Next, proteins involved in vasodilation/natriuresis are discussed with emphasis on natriuretic peptides, guanylin/uroguanylin, and nitric oxide. The renin angiotensin aldosterone system has an important role antagonizing the vasodilatory cyclic GMP system.

Identification and characterization of KLK-L4, a new kallikrein-like gene that appears to be down-regulated in breast cancer tissues

Kallikreins are a subgroup of serine proteases and these proteolytic enzymes have diverse physiological functions in many tissues. Growing evidence suggests that many kallikreins are implicated in carcinogenesis. In rodents, kallikreins constitute a large multigene family, but in humans, only three genes were identified. By using the positional candidate gene approach, we were able to identify a new kallikrein-like gene, tentatively named KLK-L4 (for kallikrein-like gene 4). This new gene maps to chromosome 19q13. 3-q13.4, is formed of five coding exons and four introns, and shows structural similarity to other kallikreins and kallikrein-like genes. KLK-L4 is expressed in a variety of tissues including prostate, salivary gland, breast, and testis. Our preliminary results show that KLK-L4 is down-regulated, at the mRNA level, in breast cancer tissues and breast cancer cell lines. Its expression is regulated by steroid hormones in the breast cancer cell line BT-474. This gene may be involved in the pathogenesis and/or progression of breast cancer and may find applicability as a novel cancer biomarker.

The expanded human kallikrein gene family: locus characterization and molecular cloning of a new member, KLK-L3 (KLK9)

In rodents, kallikreins are encoded by a large multigene family but in humans, only three kallikrein genes were thought to exist. Based on the homology between the human and the rodent kallikrein loci, we defined a 300-kb human kallikrein gene region on chromosome 19q13. 3-q13.4. By using linear sequence information, restriction analysis, PCR, and blotting techniques, we were able to construct the first detailed map of the human kallikrein gene locus. Comparative analysis of genes located in this area enabled us to expand the human kallikrein multigene family with some recently identified serine proteases and establish common structural features. We further identified a new kallikrein-like gene, named kallikrein-like gene 3 (KLK-L3; HGMW-approved symbol KLK9). We describe the structural characterization of the KLK-L3 gene, together with its precise chromosomal localization in relation to other kallikreins and its tissue expression pattern and hormonal regulation.

Genomic organization, mapping, tissue expression, and hormonal regulation of trypsin-like serine protease (TLSP PRSS20), a new member of the human kallikrein gene family

The cDNA for the trypsin-like serine protease gene (TLSP, HGMW-approved symbol PRSS20) has been recently identified. TLSP is expressed in brain and skin tissues but little else is known about this new serine protease gene. In this paper, we describe the complete genomic organization and precise mapping of the TLSP gene. This gene spans 5.3 kb of genomic sequence on chromosome 19q13.3-q13. 4. The gene consists of six exons, the first of which is untranslated. All splice junctions follow the GT/AG rule, and the intron phases are identical to those of other kallikrein-like genes, including zyme (PRSS9), NES1 (PRSSL1), and neuropsin (PRSS19). Fine-mapping of the area indicates that TLSP lies downstream from the PSA, zyme, neuropsin, and NES1 genes. Significant sequence homologies were found between TLSP and other human kallikreins. Furthermore, there is conservation of the catalytic triad (histidine, aspartic acid, serine) and of the number of coding exons (five; the same in all members of the kallikrein gene family). We thus suggest that TLSP is a new member of the human kallikrein gene family. TLSP is expressed in many tissues including cerebellum, prostate, salivary glands, stomach, lung, thymus, small intestine, spleen, liver, and uterus. TLSP expression appears to be regulated by steroid hormones in the breast carcinoma cell line BT-474.

The new kallikrein-like gene, KLK-L2. Molecular characterization, mapping, tissue expression, and hormonal regulation

Since in rodents the kallikreins are represented by a large multi-gene family, the restriction of this family in humans to three genes is somewhat surprising. In an effort to identify new human kallikrein genes, we examined a genomic area of about 300 kilobases on chromosome 19q13.3-q13.4, a region that contains most of the currently known kallikreins. By using the positional candidate approach, we were able to identify a new gene named KLK-L2 (for kallikrein- like gene 2). Screening of human EST libraries allowed us to delineate the full genomic and cDNA structure of the new gene. KLK-L2 consists of 5 coding exons and 4 introns and has significant similarities to other members of the kallikrein multi-gene family. Homology studies suggest that the protein is likely secreted. KLK-L2 is expressed mainly in breast, brain, and testis and to a lesser extent in many other tissues. KLK-L2 is up-regulated by estrogens and progestins in the breast cancer cell line BT-474.

Molecular characterization of zyme/protease M/neurosin (PRSS9), a hormonally regulated kallikrein-like serine protease

The cDNA for the zyme/protease M/neurosin gene (HGMW-approved symbol PRSS9) has recently been identified. Zyme appears to play a role in Alzheimer disease as well as in breast cancer. In this paper, we describe the complete genomic organization of the zyme gene. Zyme spans 10.5 kb of genomic sequence on chromosome 19q13.3-q13.4. The gene consists of seven exons, the first two of which are untranslated. All splice junctions follow the GT/AG rule, and the intron phases are identical to those of many other genes belonging to the same family, i.e., the kallikreins, NES1, and neuropsin. Fine-mapping of the genomic locus indicates that zyme lies upstream of the NES1 gene and downstream from the PSA and KLK2 genes. Tissue expression studies indicate that zyme is expressed mainly in brain tissue, including spinal cord and cerebellum, in mammary gland, and in kidney and uterus. Zyme is regulated by steroid hormones in the breast carcinoma cell line BT-474. Estrogens and progestins, and to a lesser extent androgens, up-regulate the zyme gene in a dose-dependent manner.

Localization of a new prostate-specific antigen-related serine protease gene, KLK4, is evidence for an expanded human kallikrein gene family cluster on chromosome 19q13.3-13.4

The human tissue kallikrein (KLK) family of serine proteases, which is important in post-translational processing events, currently consists of just three genes-tissue kallikrein (KLK1), KLK2, and prostate-specific antigen (PSA) (KLK3)-clustered at chromosome 19q13. 3-13.4. We identified an expressed sequence tag from an endometrial carcinoma cDNA library with 50% identity to the three known KLK genes. Primers designed to putative exon 2 and exon 3 regions from this novel kallikrein-related sequence were used to polymerase chain reaction-screen five cosmids spanning 130 kb around the KLK locus on chromosome 19. This new gene, which we have named KLK4, is 25 kb downstream of the KLK2 gene and follows a region that includes two other putative KLK-like gene fragments. KLK4 spans 5.2 kb, has an identical genomic structure-five exons and four introns-to the other KLK genes and is transcribed on the reverse strand, in the same direction as KLK1 but opposite to that of KLK2 and KLK3. It encodes a 254-amino acid prepro-serine protease that is most similar (78% identical) to pig enamel matrix serine protease but is also 37% identical to PSA. These data suggest that the human kallikrein gene family locus on chromosome 19 is larger than previously thought and also indicate a greater sequence divergence within this family compared with the highly conserved rodent kallikrein genes.

Gene structure of the P100 serine-protease component of the human Ra-reactive factor

The Ra-reactive factor (RaRF) is a complement dependent anti-microbial factor that reacts with numerous microorganisms such as viruses, bacteria, fungi and protozoa. It is a complex of a mannan-binding lectin (MBL) and the serine protease, P100 (MASPI). P100 activates the C4 component of the complement system and its domain organization is similar to C1r and C1s. In this study, determination was made of the structure of the human P100 gene which was found longer than 67 kbp and to be comprised of 16 exons. Its non-protease region consisted of 10 exons, as in the case of C1r and C1s, and the introns were found present in the boundary separating two CUB domains, an EGF-like domain and two CCP domains and each CUB and CCP domain contained extra internal introns. The serine protease region was comprised of 6 exons in contrast to C1r and C1s, either of which consists of a single exon. The exon-intron structure was found to reflect the evolution of these molecules and P100 to have derived earlier in the stage of evolution than C1r or C1s.

Racial differences in renal kallikrein excretion: effect of the ovulatory cycle

BACKGROUND

Renal kallikrein excretion is diminished in essential hypertension, especially in African-Americans, and evidence exists for a major gene effect on the kallikrein phenotype. In addition, urinary kallikrein excretion differs by gender, with ovulating females having greater kallikrein excretion than males or postmenopausal females. Recent studies have shown that renal kallikrein excretion varies in females during the ovulatory cycle, with levels rising during the luteal phase and returning during the follicular phase to levels that are similar to those of males. In family studies, gender differences in urinary kallikrein excretion were present in white subjects, but not black subjects. We therefore hypothesized dysregulation of kallikrein biosynthetic responses in African-Americans.

METHODS

We determined urinary kallikrein activity [chromogenic substrate S2266 (D-val-leu-arg-paranitroanilide) assay; in microU/mg creatinine] in white (N = 15) and black (N = 11) ovulating females during the ovulatory cycle. Serum progesterone, estrogen, plasma renin activity as well as urinary aldosterone, and urinary electrolytes were determined to investigate changes between mid-follicular and mid-luteal phases in the two groups.

RESULTS

White and black groups were matched for age, body mass index, blood pressure, heart rate and renal function. Ovulatory cycle phases were confirmed by serum progesterone determinations, which increased significantly in whites and blacks to a comparable degree [0.84 +/- 0.14 nmol/liter (mid-follicular) to 29.77 +/- 4.70 nmol/liter (mid-luteal) in whites, 0.67 +/- 0.08 nmol/liter (mid-follicular) to 28.62 +/- 5.83 nmol/liter (mid-luteal) in blacks; P < 0.001 for cycle effect, P = NS for race effect and race X cycle interaction]. Urinary kallikrein activity increased from 623 +/- 86 microU/mg creatinine (mid-follicular) to 948 +/- 142 microU/mg creatinine (mid-luteal) in whites, but did not change in blacks during the ovulatory cycle [239 +/- 73 microU/mg creatinine (mid-follicular] to 244 +/- 41 microU/mg creatinine (mid-luteal)]. Two-way ANOVA revealed significant effects on urinary kallikrein for race (P < 0.001), cycle (P < 0.05), and race X cycle interaction (P < 0.05). Thus, white females had higher urinary kallikrein than black females, and demonstrated a significant increase in urinary kallikrein excretion during the ovulatory cycle, whereas no significant change in urinary kallikrein activity was seen in the black group. Enzyme kinetic studies and mixing studies demonstrated that these racial differences in renal kallikrein excretion were quantitative, rather than due to qualitative differences in the renal kallikrein enzyme or due to the presence of a kallikrein inhibitor.

CONCLUSIONS

These results suggest pronounced blunting of menstrual cycle changes in urinary kallikrein excretion in black females. Blunted urinary kallikrein responses during the ovulatory cycle are consistent with dysregulation of renal kallikrein biosynthetic responses in African-Americans, a group at increased risk for hypertension.

Pathophysiology of the kallikrein-kinin system in mammalian nervous tissue

The nervous system and peripheral tissues in mammals contain a large number of biologically active peptides and proteases that function as neurotransmitters or neuromodulators in the nervous system, as hormones or cellular mediators in peripheral tissue, and play a role in human neurological diseases. The existence and possible functional relevance of bradykinin and kallidin (the peptides), kallikreins (the proteolytic enzymes), and kininases (the peptidases) in neurophysiology and neuropathological states are discussed in this review. Tissue kallikrein, the major cellular kinin-generating enzyme, has been localised in various areas of the mammalian brain. Functionally, it may assist also in the normal turnover of brain proteins and the processing of peptide-hormones, neurotransmitters, and some of the nerve growth factors that are essential for normal neuronal function and synaptic transmission. A specific class of kininases, peptidases responsible for the rapid degradation of kinins, is considered to be identical to enkephalinase A. Additionally, kinins are known to mediate inflammation, a cardinal feature of which is pain, and the clearest evidence for a primary neuronal role exists so far in the activation by kinins of peripherally located nociceptive receptors on C-fibre terminals that transmit and modulate pain perception. Kinins are also important in vascular homeostasis, the release of excitatory amino acid neurotransmitters, and the modulation of cerebral cellular immunity. The two kinin receptors, B2 and B1, that modulate the cellular actions of kinins have been demonstrated in animal neural tissue, neural cells in culture, and various areas of the human brain. Their localisation in glial tissue and neural centres, important in the regulation of cardiovascular homeostasis and nociception, suggests that the kinin system may play a functional role in the nervous system.

Human Kallikrein 2 (hK2) and prostate-specific antigen (PSA): two closely related, but distinct, kallikreins in the prostate

Recent studies on human kallikrein 2 (hK2) have revealed striking similarities and significant differences with the closely related kallikrein PSA. Both PSA and hK2 are primarily localized to the prostate and share close structural similarities. Although both kallikreins are produced by the same secretory epithelial cells in the prostate, hK2 is associated more with prostate tumors than PSA and is highly expressed in poorly differentiated cancer cells. The potent trypsin-like activity of hK2 contrasts with the weak chymotrypsin-like activity of PSA. The inactive precursor form of PSA, proPSA, is converted rapidly to active PSA by hK2, suggesting an important in vivo regulatory function by hK2 on PSA activity. The high homology between hK2 and PSA results in significant cross-reactivity to hK2 by polyclonal and some monoclonal antibodies to PSA. Future studies on both PSA and hK2 need to take into account this potential for cross-reactivity. Specific monoclonal antibodies to hK2 have now demonstrated that serum levels of hK2, like PSA, are correlated with prostate cancer. The production of hK2 protein in active protease form and specific monoclonal antibodies to the hK2 antigen will allow extensive future studies delineating the physiological and clinical utility of this new prostate antigen.

Structural characterization and mapping of the normal epithelial cell-specific 1 gene

The normal epithelial cell-specific 1 (NES1) gene is a recently identified novel serine protease-like gene which is down-regulated during breast cancer progression. The gene product has 34-42% identity with the members of three distinct serine protease families: the trypsin-like family, activators of kringle domain-containing growth factors, and the kallikrein family (X. L. Liu et al., (1996) Cancer Res 56, 3371-3379). Although the cDNA of this gene has been cloned, its genomic structure and chromosomal position are not as yet known. Here, we report the genomic characterization and mapping of the NES1 gene. By subcloning and sequencing a PAC clone containing the complete NES1 gene, we were able to characterize the structure of this gene. The NES1 gene spans 5.5 kb and is composed of five coding exons and one untranslated exon. The positions of the introns were similar to trypsinogen, prostate specific antigen (PSA), and tissue plasminogen activator (TPA). NES1 gene was also localized with somatic cell mapping, radiation hybrid mapping, and fluorescence in situ hybridization techniques to chromosome 19q13.3-q13.4, the same region where the human kallikrein gene family resides. Taken together, our results suggest that the NES1 gene originates from the same ancestor as trypsinogen, PSA, and TPA, but remains in close proximity to PSA.

Identification of human plasma kallikrein gene polymorphisms and evaluation of their role in end-stage renal disease

Kallikreins are serine proteases that release kinins from kininogens. Kinins, via their effects on cardiovascular and renal function, may be involved in the pathogenesis of hypertension and renal failure. Two groups of kallikreins exist, glandular or tissue kallikrein and plasma kallikrein. In this study, we examined the human plasma kallikrein gene KLK3 to determine whether it contributed to end-stage renal disease (ESRD) susceptibility. We identified two novel polymorphic sequences closely linked to the KLK3 gene, designated KLK3b and KLK3c (heterozygosities: 0.64 to 0.68 and 0.48 to 0.52, respectively). We mapped the KLK3 gene and the marker KLK3c to the long arm of human chromosome 4 between F11 and D4S426 using a radiation hybrid panel. The study population consisted of 142 sibling pairs concordant for ESRD from 121 African American families. The 142 sibling pairs were stratified into 78 pairs with hypertension- and chronic glomerulonephritis-associated ESRD and 64 with non-insulin-dependent diabetes mellitus-associated ESRD. Linkage analyses, using SIBPAL of SAGE, and exclusion analysis, using MAPMAKERS/SIBS, were performed. Linkage analysis of affected sibling pairs did not reveal any evidence of linkage of KLK3 to ESRD in all 142 sib-pairs or in the two stratified subsets. Exclusion analysis indicated that the KLK3 gene could be excluded from contributing to ESRD at a relative risk of 3 when the maximum log of the odds score of -2 was used as the criterion for exclusion. However, an association analysis using the relative predispositional effect technique showed that alleles 7 and 9 of KLK3b were consistently associated with ESRD. Alleles 7 and 9 were present in 11.2% and 10.8% of the 113 unrelated ESRD probands and in 6.6% and 6.6% of the 204 race-matched control subjects without renal disease (allele P=.0041 and .0016, respectively). Alleles 7 and 9 were also present in 13% and 10.4% of the proband's first siblings (allele P=.00014 and .0087, respectively). The association of KLK3b alleles with ESRD raises the possibility that polymorphisms in KLK3 may play a role in ESRD susceptibility. The lack of linkage might reflect our relatively small family set.