Organization and evolution of the glandular kallikrein locus in Mus musculus

Deregulation of the Kallikrein Protease Family in the Salivary Glands of the Sjögren's Syndrome ERdj5 Knockout Mouse Model

Introduction

The purpose of this study was to identify differentially expressed proteins in salivary glands of the ERdj5 knockout mouse model for Sjögren's syndrome and to elucidate possible mechanisms for the morbid phenotype development. At the same time, we describe for the first time the sexual dimorphism of the murine submandibular salivary gland at the proteome level.

Methods

We performed Liquid Chromatography/Mass Spectrometry in salivary gland tissues from both sexes of ERdj5 knockout and 129SV wildtype mice. The resulting list of proteins was evaluated with bioinformatic analysis and selected proteins were validated by western blot and immunohistochemistry and further analyzed at the transcription level by qRT-PCR.

Results

We identified 88 deregulated proteins in females, and 55 in males in wildtype vs knockout comparisons. In both sexes, Kallikrein 1b22 was highly upregulated (fold change>25, ANOVA p<0.0001), while all other proteases of this family were either downregulated or not significantly affected by the genotype. Bioinformatic analysis revealed a possible connection with the downregulated NGF that was further validated by independent methods. Concurrently, we identified 416 proteins that were significantly different in the salivary gland proteome of wildtype female vs male mice and highlighted pathways that could be driving the strong female bias of the pathology.

Conclusion

Our research provides a list of novel targets and supports the involvement of an NGF-mediating proteolytic deregulation pathway as a focus point towards the better understanding of the underlying mechanism of Sjögren's syndrome.

Old genes and new genes: The evolution of the kallikrein locus

The human kallikrein locus consists of KLK1, the gene of major tissue kallikrein, and 14 genes of kallikrein-related peptidases (KLKs) located in tandem on chromosome 19q13.3-13.4. In this review, based on information retrieved from the literature or extracted from genome databases, it is hypothesised that the kallikrein locus is unique to mammals. The majority of genes are highly conserved, as demonstrated by the identification of 11 KLK genes in the opossum, a metatherian species. In contrast, a sublocus, encompassing KLK1-4, has gone through major transformations that have generated new genes, which in most cases are closely related to KLK1. In the primate lineage, this process created KLK3, the gene of the prostate cancer marker, prostate-specific antigen (PSA), whereas in the murine lineage it gave rise to 13 genes unique to the mouse and nine unique to the rat. The KLK proteases are effector molecules that emerged early in mammalian evolution and their importance in skin homeostasis and male reproductive function is undisputed and there are also accumulating evidence for a role of KLK proteases in the development of the brain. It is speculated that the KLK gene family arose as part of the process that generated distinguishing mammalian features, like skin with hair and sweat glands, and specialised anatomical attributes of the brain and the reproductive tract.

Transcriptome reveals the overexpression of a kallikrein gene cluster (KLK1/3/7/8/12) in the Tibetans with high altitude-associated polycythemia

High altitude-associated polycythemia (HAPC) is a very common disease. However, it the disease is still unmanageable and the related molecular mechanisms remain largely unclear. In the present study, we aimed to explore the molecular mechanisms responsible for the development of HAPC using transcriptome analysis. Transcriptome analysis was conducted in 3 pairs of gastric mucosa tissues from patients with HAPC and healthy residents at a similar altitude. Endoscopy and histopathological analyses were used to examine the injury to gastric tissues. Molecular remodeling was performed for the interaction between different KLK members and cholesterol. HAPC was found to lead to morphological changes and pathological damage to the gastric mucosa of patients. A total of 10,304 differentially expressed genes (DEGs) were identified. Among these genes, 4,941 DEGs were upregulated, while 5,363 DEGs were downregulated in the patients with HAPC (fold change ≥2, P<0.01 and FDR <0.01). In particular, the kallikrein gene cluster (KLK1/3/7/8/12) was upregulated >17-fold. All the members had high-score binding cholesterol, particularly for the polymers of KLK7. The kallikrein gene cluster (KLK1/3/7/8/12) is on chromosome 19q13.3-13.4. The elevated levels of KLK1, KLK3, KLK7, KLK8 and KLK12 may be closely associated with the hypertension, inflammation, obesity and other gastric injuries associated with polycythemia. The interaction of KLKs and cholesterol maybe play an important role in the development of hypertension. The findings of the present study revealed that HAPC induces gastric injury by upregulating the kallikrein gene cluster (KLK1/3/7/8/12), which can bind cholesterol and result in kallikrein hypertension. These findings provide some basic information for understanding the molecular mechanisms responsible for HAPC and HAPC-related diseases.

Oviductal estrogen receptor α signaling prevents protease-mediated embryo death

Development of uterine endometrial receptivity for implantation is orchestrated by cyclic steroid hormone-mediated signals. It is unknown if these signals are necessary for oviduct function in supporting fertilization and preimplantation development. Here we show that conditional knockout (cKO) mice lacking estrogen receptor α (ERα) in oviduct and uterine epithelial cells have impaired fertilization due to a dramatic reduction in sperm migration. In addition, all successfully fertilized eggs die before the 2-cell stage due to persistence of secreted innate immune mediators including proteases. Elevated protease activity in cKO oviducts causes premature degradation of the zona pellucida and embryo lysis, and wild-type embryos transferred into cKO oviducts fail to develop normally unless rescued by concomitant transfer of protease inhibitors. Thus, suppression of oviductal protease activity mediated by estrogen-epithelial ERα signaling is required for fertilization and preimplantation embryo development. These findings have implications for human infertility and post-coital contraception.

DOI:http://dx.doi.org/10.7554/eLife.10453.001

In female mammals, eggs made in the ovaries travel to the uterus via tubes called oviducts (or Fallopian tubes). If sperm fertilize these eggs on the way, they complete this journey as early embryos and then implant into the wall of the uterus. As sperm and then newly fertilized embryos travel down these tubes, they encounter fluid inside the oviduct, which is generated by the cells that line the tube.

The hormonal changes that occur with the menstrual cycle alter the complexity and cellular composition of the uterus. When an egg is fertilized, further changes in the levels of the hormones, estrogen and progesterone, ensure the uterus becomes receptive to the embryo. However, it remains unknown whether such hormone-mediated signals also regulate the oviduct to support fertilization and early embryo development.

To investigate this question, Winuthayanon et al. studied female mice that lack an important estrogen receptor in the cells that line their oviducts and uterus. These mice are infertile. This is partly because most sperm become stuck in the uterus and fail to reach the eggs in the oviduct in order to fertilize them. The oviduct also becomes a hostile environment for both eggs and embryos, as reflected in damaged eggs and the complete loss of all new embryos by two days after fertilization. These embryos die, not because their development fails, but because their outer membrane becomes damaged and breaks apart. Winuthayanon et al. showed that this is due to the persistence of enzymes that form part of the immune system inside the oviduct. These enzymes can degrade proteins and damage cell membranes.

The presence of this estrogen receptor on the inner lining of the oviduct thus appears to be crucially important for reproduction (these effects were not seen when it is removed from other cells of the oviduct). The loss of this receptor also reveals the vital role that estrogen plays in suppressing parts of the immune response to ensure the oviduct provides a supportive environment for fertilization and embryo development. These findings could also have future application in the development of new contraceptives and might also shed light on the causes of human infertility.

DOI:http://dx.doi.org/10.7554/eLife.10453.002

Glutathione S-transferase P protects against cyclophosphamide-induced cardiotoxicity in mice

High-dose chemotherapy regimens using cyclophosphamide (CY) are frequently associated with cardiotoxicity that could lead to myocyte damage and congestive heart failure. However, the mechanisms regulating the cardiotoxic effects of CY remain unclear. Because CY is converted to an unsaturated aldehyde acrolein, a toxic, reactive CY metabolite that induces extensive protein modification and myocardial injury, we examined the role of glutathione S-transferase P (GSTP), an acrolein-metabolizing enzyme, in CY cardiotoxicity in wild-type (WT) and GSTP-null mice. Treatment with CY (100-300 mg/kg) increased plasma levels of creatine kinase-MB isoform (CK · MB) and heart-to-body weight ratio to a significantly greater extent in GSTP-null than WT mice. In addition to modest yet significant echocardiographic changes following acute CY-treatment, GSTP insufficiency was associated with greater phosphorylation of c-Jun and p38 as well as greater accumulation of albumin and protein-acrolein adducts in the heart. Mass spectrometric analysis revealed likely prominent modification of albumin, kallikrein-1-related peptidase, myoglobin and transgelin-2 by acrolein in the hearts of CY-treated mice. Treatment with acrolein (low dose, 1-5 mg/kg) also led to increased heart-to-body weight ratio and myocardial contractility changes. Acrolein induced similar hypotension in GSTP-null and WT mice. GSTP-null mice also were more susceptible than WT mice to mortality associated with high-dose acrolein (10-20 mg/kg). Collectively, these results suggest that CY cardiotoxicity is regulated, in part, by GSTP, which prevents CY toxicity by detoxifying acrolein. Thus, humans with low cardiac GSTP levels or polymorphic forms of GSTP with low acrolein-metabolizing capacity may be more sensitive to CY toxicity.

Quantitative analysis of protein and gene expression in salivary glands of Sjogren's-like disease NOD mice treated by bone marrow soup

Background

Bone marrow cell extract (termed as BM Soup) has been demonstrated to repair irradiated salivary glands (SGs) and restore saliva secretion in our previous study. In the present study, we aim to investigate if the function of damaged SGs in non-obese diabetic (NOD) mice can be restored by BM Soup treatment and the molecular alterations associated with the treatment.

Methods

Whole BM cells were lysed and soluble intracellular contents (“BM Soup”) were injected I.V. into NOD mice. Tandem mass tagging with 2-D liquid chromatography-mass spectrometry was used to quantify proteins in the submandibular glands (SMGs) between untreated and BM Soup-treated mice. Quantitative PCR was used to identify genes with altered expression in the treated mice.

Results BM Soup

restored salivary flow rates to normal levels and significantly reduced the focus scores of SMGs in NOD mice. More than 1800 proteins in SMG cells were quantified by the proteomic approach. Many SMG proteins involved in inflammation and apoptosis were found to be down-regulated whereas those involved in salivary gland biology and development/regeneration were up-regulated in the BM Soup-treated mice. qPCR analysis also revealed expression changes of growth factors and cytokines in the SMGs of the treated NOD mice.

Conclusion

BM Soup treatment is effective to restore the function of damaged SGs in NOD mice. Through gene/protein expression analysis, we have found that BM Soup treatment might effectuate via inhibiting apoptosis, focal adhesion and inflammation whereas promoting development, regeneration and differentiation of the SG cells in NOD mice. These findings provide important insights on the potential mechanisms underlying the BM Soup treatment for functional restoration of damaged SGs in NOD mice. Additional studies are needed to further confirm the identified target genes and their related signaling pathways that are responsible for the BM Soup treatment.

Characterization of Spink6 in mouse skin: the conserved inhibitor of kallikrein-related peptidases is reduced by barrier injury

The proteolytic regulation of the desquamation process by kallikrein-related peptidases (KLKs) is crucial for epidermal barrier function, and elevated KLK levels have been reported in atopic dermatitis. KLKs are controlled by specific inhibitors of the serine protease inhibitor of Kazal-type (Spink) family. Recently, SPINK6 was shown to be present in human stratum corneum. In order to investigate its role in epidermal barrier function, we studied mouse Spink6. Sequence alignment revealed that the Kazal domain of Spink6 is highly conserved in animals. Recombinant Spink6 efficiently inhibited mouse Klk5 and human KLK2, KLK4, KLK5, KLK6, KLK7, KLK12, KLK13, and KLK14, whereas human KLK1 and KLK8 were not inhibited. Spink6 was expressed in mouse epidermis mainly in the stratum granulosum, and the inner root sheath of hair follicles. Stimulation with flagellin, EGF, and IL-1β did not alter Spink6 expression, whereas stimulation with tumor necrosis factor-α (TNFα)/IFNγ and all-trans retinoic acid resulted in a significant downregulation of Spink6 expression in cultured primary mouse keratinocytes. Mechanically and metabolically induced skin barrier dysfunction resulted both in a downregulation of Spink6 expression. Our study indicates that Spink6 is a potent inhibitor of KLKs and involved in skin barrier function.

Identification of ejaculated proteins in the house mouse (Mus domesticus) via isotopic labeling

BACKGROUND

Seminal fluid plays an important role in successful fertilization, but knowledge of the full suite of proteins transferred from males to females during copulation is incomplete. The list of ejaculated proteins remains particularly scant in one of the best-studied mammalian systems, the house mouse (Mus domesticus), where artificial ejaculation techniques have proven inadequate. Here we investigate an alternative method for identifying ejaculated proteins, by isotopically labeling females with 15N and then mating them to unlabeled, vasectomized males. Proteins were then isolated from mated females and identified using mass spectrometry. In addition to gaining insights into possible functions and fates of ejaculated proteins, our study serves as proof of concept that isotopic labeling is a powerful means to study reproductive proteins.

RESULTS

We identified 69 male-derived proteins from the female reproductive tract following copulation. More than a third of all spectra detected mapped to just seven genes known to be structurally important in the formation of the copulatory plug, a hard coagulum that forms shortly after mating. Seminal fluid is significantly enriched for proteins that function in protection from oxidative stress and endopeptidase inhibition. Females, on the other hand, produce endopeptidases in response to mating. The 69 ejaculated proteins evolve significantly more rapidly than other proteins that we previously identified directly from dissection of the male reproductive tract.

CONCLUSION

Our study attempts to comprehensively identify the proteins transferred from males to females during mating, expanding the application of isotopic labeling to mammalian reproductive genomics. This technique opens the way to the targeted monitoring of the fate of ejaculated proteins as they incubate in the female reproductive tract.

Evolutionary history of tissue kallikreins

The gene family of human kallikrein-related peptidases (KLKs) encodes proteins with diverse and pleiotropic functions in normal physiology as well as in disease states. Currently, the most widely known KLK is KLK3 or prostate-specific antigen (PSA) that has applications in clinical diagnosis and monitoring of prostate cancer. The KLK gene family encompasses the largest contiguous cluster of serine proteases in humans which is not interrupted by non-KLK genes. This exceptional and unique characteristic of KLKs makes them ideal for evolutionary studies aiming to infer the direction and timing of gene duplication events. Previous studies on the evolution of KLKs were restricted to mammals and the emergence of KLKs was suggested about 150 million years ago (mya). In order to elucidate the evolutionary history of KLKs, we performed comprehensive phylogenetic analyses of KLK homologous proteins in multiple genomes including those that have been completed recently. Interestingly, we were able to identify novel reptilian, avian and amphibian KLK members which allowed us to trace the emergence of KLKs 330 mya. We suggest that a series of duplication and mutation events gave rise to the KLK gene family. The prominent feature of the KLK family is that it consists of tandemly and uninterruptedly arrayed genes in all species under investigation. The chromosomal co-localization in a single cluster distinguishes KLKs from trypsin and other trypsin-like proteases which are spread in different genetic loci. All the defining features of the KLKs were further found to be conserved in the novel KLK protein sequences. The study of this unique family will further assist in selecting new model organisms for functional studies of proteolytic pathways involving KLKs.

Kallikreins on steroids: structure, function, and hormonal regulation of prostate-specific antigen and the extended kallikrein locus

The 15 members of the kallikrein-related serine peptidase (KLK) family have diverse tissue-specific expression profiles and putative proteolytic functions. The kallikrein family is also emerging as a rich source of disease biomarkers with KLK3, commonly known as prostate-specific antigen, being the current serum biomarker for prostate cancer. The kallikrein locus is also notable because it is extraordinarily responsive to steroids and other hormones. Indeed, at least 14 functional hormone response elements have been identified in the kallikrein locus. A more comprehensive understanding of the transcriptional regulation of kallikreins may help the field make more informed hypotheses about the physiological functions of kallikreins and their effectiveness as biomarkers. In this review, we describe the organization of the kallikrein locus and the structure of kallikrein genes and proteins. We also focus on the transcriptional regulation of kallikreins by androgens, progestins, glucocorticoids, mineralocorticoids, estrogens, and other hormones in animal models and human prostate, breast, and reproductive tract tissues. The interaction of the androgen receptor with androgen response elements in the promoter and enhancer of KLK2 and KLK3 is also summarized in detail. There is evidence that all kallikreins are regulated by multiple nuclear receptors. Yet, apart from KLK2 and KLK3, it is not clear whether all kallikreins are direct transcriptional targets. Therefore, we argue that gaining more detailed information about the mechanisms that regulate kallikrein expression should be a priority of future studies and that the kallikrein locus will continue to be an important model in the era of genome-wide analyses.

Natural and synthetic inhibitors of kallikrein-related peptidases (KLKs)

Including the true tissue kallikrein KLK1, kallikrein-related peptidases (KLKs) represent a family of fifteen mammalian serine proteases. While the physiological roles of several KLKs have been at least partially elucidated, their activation and regulation remain largely unclear. This obscurity may be related to the fact that a given KLK fulfills many different tasks in diverse fetal and adult tissues, and consequently, the timescale of some of their physiological actions varies significantly. To date, a variety of endogenous inhibitors that target distinct KLKs have been identified. Among them are the attenuating Zn(2+) ions, active site-directed proteinaceous inhibitors, such as serpins and the Kazal-type inhibitors, or the huge, unspecific compartment forming α(2)-macroglobulin. Failure of these inhibitory systems can lead to certain pathophysiological conditions. One of the most prominent examples is the Netherton syndrome, which is caused by dysfunctional domains of the Kazal-type inhibitor LEKTI-1 which fail to appropriately regulate KLKs in the skin. Small synthetic inhibitory compounds and natural polypeptidic exogenous inhibitors have been widely employed to characterize the activity and substrate specificity of KLKs and to further investigate their structures and biophysical properties. Overall, this knowledge leads not only to a better understanding of the physiological tasks of KLKs, but is also a strong fundament for the synthesis of small compound drugs and engineered biomolecules for pharmaceutical approaches. In several types of cancer, KLKs have been found to be overexpressed, which makes them clinically relevant biomarkers for prognosis and monitoring. Thus, down regulation of excessive KLK activity in cancer and in skin diseases by small inhibitor compounds may represent attractive therapeutical approaches.

Early over expression of messenger RNA for multiple genes, including insulin, in the Pancreatic Lymph Nodes of NOD mice is associated with Islet Autoimmunity

BACKGROUND

Autoimmune diabetes (T1D) onset is preceded by a long inflammatory process directed against the insulin-secreting beta cells of the pancreas. Deciphering the early autoimmune mechanisms represents a challenge due to the absence of clinical signs at early disease stages. The aim of this study was to identify genes implicated in the early steps of the autoimmune process, prior to inflammation, in T1D. We have previously established that insulin autoantibodies (E-IAA) predict early diabetes onset delineating an early phenotypic check point (window 1) in disease pathogenesis. We used this sub-phenotype and applied differential gene expression analysis in the pancreatic lymph nodes (PLN) of 5 weeks old Non Obese Diabetic (NOD) mice differing solely upon the presence or absence of E-IAA. Analysis of gene expression profiles has the potential to provide a global understanding of the disease and to generate novel hypothesis concerning the initiation of the autoimmune process.

METHODS

Animals have been screened weekly for the presence of E-IAA between 3 and 5 weeks of age. E-IAA positive or negative NOD mice at least twice were selected and RNAs isolated from the PLN were used for microarray analysis. Comparison of transcriptional profiles between positive and negative animals and functional annotations of the resulting differentially expressed genes, using software together with manual literature data mining, have been performed.

RESULTS

The expression of 165 genes was modulated between E-IAA positive and negative PLN. In particular, genes coding for insulin and for proteins known to be implicated in tissue remodelling and Th1 immunity have been found to be highly differentially expressed. Forty one genes showed over 5 fold differences between the two sets of samples and 30 code for extracellular proteins. This class of proteins represents potential diagnostic markers and drug targets for T1D.

CONCLUSION

Our data strongly suggest that the immune related mechanisms taking place at this early age in the PLN, correlate with homeostatic changes influencing tissue integrity of the adjacent pancreatic tissue. Functional analysis of the identified genes suggested that similar mechanisms might be operating during pre-inflammatory processes deployed in tissues i) hosting parasitic microorganisms and ii) experiencing unrestricted invasion by tumour cells.

S1′ and S2′ subsite specificities of human plasma kallikrein and tissue kallikrein 1 for the hydrolysis of peptides derived from the bradykinin domain of human kininogen

The S1′ and S2′ subsite specificities of human tissue kallikrein 1 (KLK1) and human plasma kallikrein (HPK) were examined with the peptide series Abz-GFSPFRXSRIQ-EDDnp and Abz-GFSPFRSXRIQ-EDDnp [X=natural amino acids or S(PO3H2)]. KLK1 efficiently hydrolyzed most of the peptides except those containing negatively charged amino acids at P1′ and P2′ positions. Abz-GFSPFRSSRIQ-EDDnp, as in human kininogen, is the best substrate for KLK1 and exclusively cleaved the R-S bond. All other peptides were cleaved also at the F-R bond. The synthetic human kininogen segment Abz-MISLMKRPPGFSPFRS390S391RI-NH2was hydrolyzed by KLK1 first at R-S and then at M-K bonds, releasing Lys-bradykinin. In the S390and S391phosphorylated analogs, this order of hydrolysis was inverted due to the higher resistance of the R-S bond. Abz-MISLMKRPPG-FSPFRSS(PO3H2)391RI-NH2was hydrolyzed by KLK1 at M-K and mainly at the F-R bond, releasing des-(Arg9)-Lys-Bk which is a B1 receptor agonist. HPK cleaved all the peptides at R and showed restricted specificity for S in the S1′ subsite, with lower specificity for the S2′ subsite. Abz-MISLMKRPPGFSPFRSSRI-NH2was efficiently hydrolyzed by HPK under bradykinin release, while the analogs containing S(PO3H2) were poorly hydrolyzed. In conclusion, S1′ and S2′ subsite specificities of KLK1 and HPK showed peculiarities that were observed with substrates containing the amino acid sequence of human kininogen.

Reflections on the tissue kallikrein and kallikrein-related peptidase family – from mice to men – what have we learnt in the last two decades?

The genes encoding the kininogenase, glandular tissue kallikrein, in rodents and man were first described in the mid-1980s. Remarkably, they appeared to be part of a much larger highly conserved family of genes (GK) in rodents, but only had two paralogs in man. This discrepancy was not rectified until the late 1990s/2000 with the identification of a cluster of 12 more kallikrein-related (KLK) genes in the human 19q13 locus and the subsequent identification of their rodent homologs. Interestingly, there are remarkable similarities in expression patterns, hormonal regulation and functional attributes of the old (GK) and new (KLK) families which underscore the evolutionary conservation across these loci and species. This historical perspective focuses on the lessons learned from earlier studies on the rodentGKgene families and the striking similarities of some attributes, yet uniqueness, of others. These earlier findings have all contributed to the current status of the KLK serine peptidase-encoding gene family as an exciting source of new biomarkers and therapeutic targets.

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 novel transcript from the KLKP1 gene is androgen regulated, down-regulated during prostate cancer progression and encodes the first non-serine protease identified from the human kallikrein gene locus

BACKGROUND

The kallikrein-related (KLK) serine protease, prostate specific antigen is the current marker for prostate cancer (PCa). Other members of the KLK family are also emerging as potential adjunct biomarkers for this disease. Our aim was to identify and characterize novel KLK-related genes with potential as PCa bio-markers.

METHODS

Low stringency DNA screening was coupled with amplification techniques to identify novel sequences. Transcripts were examined by Northern blot, RT-PCR, and in situ hybridization analysis and in silico bioinformatics approaches. Protein characterization was performed by Western blot and confocal microscopy analysis. Gene regulation studies were performed by quantitative PCR and promoter reporter assays.

RESULTS

We identified a novel kallikrein-related mRNA designated KRIP1 (kallikrein-related, expressed in prostate 1) which, together with the recently reported PsiKLK1 and KLK31P transcripts, is transcribed from KLKP1; a gene evolved from, and located within, the KLK locus. Significantly, in contrast to these other non-coding KLKP1 transcripts, the KRIP1 mRNA generates an approximately 18 kDa intracellular protein-the first non-serine protease identified from the KLK locus. KRIP1 mRNA is abundant only in normal prostate and is restricted to cells of epithelial origin in normal and diseased glands. Ligand binding of the androgen receptor increases transcription from the KLKP1 gene. Consistently, KRIP1 mRNA levels are lower in PCa samples compared to benign prostatic hyperplasia.

CONCLUSIONS

Transcription from KLKP1 is reduced as cells de-differentiate on the pathway to malignancy. KLKP1/KRIP1 has potential as a marker of both PCa progression and recent evolutionary events within the KLK locus.

Characterization of mouse tissue kallikrein 5

Mouse tissue kallikreins (Klks) are members of a large, multigene family consisting of 37 genes, 26 of which can code for functional proteins. Mouse tissue kallikrein 5 (Klk5) has long been thought to be one of these functional genes, but the gene product, mK5, has not been isolated and characterized. In the present study, we prepared active recombinant mK5 using an Escherichia coli expression system, followed by column chromatography. We then determined the biochemical and enzymatic properties of purified mK5. mK5 had trypsin-like activity for Arg at the P1 position, and its activity was inhibited by typical serine protease inhibitors. mK5 degraded gelatin, fibronectin, collagen type IV, high-molecular-weight kininogen, and insulin-like growth factor binding protein-3. Our data suggest that mK5 may be implicated in the process of extracellular matrix remodeling.

Porcine kallikrein gene family: Genomic structure, mapping, and differential expression analysis

Kallikreins belong to a family of serine proteases that are widespread throughout living organisms, expressed in diverse tissue-specific patterns, and known to have highly diverse physiological functions. The 15 human and 24 mouse kallikreins have been implicated in pathophysiology of brain, kidney, and respiratory and reproductive systems and often are used as cancer biomarkers. To better elucidate the structure and evolutionary origin of this important gene family in the pig, we have constructed a contiguous BAC clone-derived physical map of the porcine kallikrein gene region and have fully sequenced a BAC clone containing 13 kallikrein genes, 11 of which are novel. Radiation hybrid mapping assigns this kallikrein-gene-rich region to porcine chromosome 6. Phylogenetic and percent identity plot-based analyses revealed strong structure and order conservation of kallikreins among four mammalian species. Reverse transcriptase-polymerase chain reaction-based expression analysis of porcine kallikreins showed a complex expression pattern across different tissues with the thymus being the only tissue expressing all 13 kallikrein genes. [The sequence data described in this paper has been submitted to GenBank under Accession No. AC149292].

Does PSA play a role as a promoting agent during the initiation and/or progression of prostate cancer?

Prostate cancer cells, like normal prostate epithelial cells, produce high levels of the differentiation marker and serine protease prostate-specific antigen (PSA). PSA is used extensively as a biomarker to screen for prostate cancer, to detect recurrence following local therapies, and to follow response to systemic therapies for metastatic disease. While much is known about PSA's role as a biomarker, only a relatively few studies address the role played by PSA in the pathobiology of prostate cancer. Autopsy studies have documented that not only do prostate cancer cells maintain production of high amounts of PSA but they also maintain the enzymatic machinery required to process PSA to an enzymatically active form. A variety studies performed over the last 10 years have hinted at a role for PSA in growth, progression, and metastases of prostate cancer. A fuller understanding of PSA's functional role in prostate cancer biology, however, has been hampered by the lack of appropriate models and tools. Therefore, the purpose of this review is not to address issues related to PSA as a biomarker. Instead, by reviewing what is known about the genetics, biochemistry, and biology of PSA in normal and malignant prostate tissue, insights may be gained into the role PSA may be playing in the pathobiology of prostate cancer that can connect measurement of this biomarker to an understanding of the underlying etiology and progression of the disease.

Long-Term Prediction of Prostate Cancer Up to 25 Years Before Diagnosis of Prostate Cancer Using Prostate Kallikreins Measured at Age 44 to 50 Years

Purpose

We examined whether prostate-specific antigen (PSA) forms and human kallikrein 2 (hK2) measured at age 44 to 50 years predict long-term risk of incident prostate cancer.

Methods

From 1974 to 1986, 21,277 men age ≤ 50 years in Malmö, Sweden, enrolled onto a cardiovascular study (74% participation). The rate of PSA screening in this population is low. According to the Swedish Cancer Registry, 498 were later diagnosed with prostate cancer. We measured hK2, free PSA, and total PSA (tPSA) in archived blood plasma from 462 participants later diagnosed with prostate cancer and from 1,222 matched controls. Conditional logistic regression was used to test for association of prostate cancer with hK2 and PSA forms measured at baseline.

Results

Median delay between venipuncture and prostate cancer diagnosis was 18 years. hK2 and all PSA forms were strongly associated with prostate cancer (all P < .0005). None of the 90 anthropometric, lifestyle, biochemical, and medical history variables measured at baseline was importantly predictive. A tPSA increase of 1 ng/mL was associated with an increase in odds of cancer of 3.69 (95% CI, 2.99 to 4.56); addition of other PSA forms or hK2 did not add to the predictive value of tPSA. tPSA remained predictive for men diagnosed ≥ 20 years after venipuncture, and the predictive value remained unchanged in an analysis restricted to palpable disease.

Conclusion

A single PSA test at age 44 to 50 years predicts subsequent clinically diagnosed prostate cancer. This raises the possibility of risk stratification for prostate cancer screening programs.

Transcriptional profiling of androgen receptor (AR) mutants suggests instructive and permissive roles of AR signaling in germ cell development

The androgen receptor (AR) is a transcription factor that plays a critical role in male sexual development, spermatogenesis, and maintenance of hormonal homeostasis. Despite the extensive knowledge of the phenotypic consequences of mutations in Ar, very little is known about the transcriptional targets of AR within the testis. To identify potential targets of androgen signaling in the testis, we have analyzed the transcriptional profile of adult testes from Ar hypomorphs alone or in combination with Sertoli cell-specific Ar ablation. Using Affymetrix MOE430A mouse genome arrays we interrogated more than 22,000 transcripts. We found the expression level of 62 transcripts in the Ar mutants differed by greater than 2-fold compared with wild type. We also found that more transcripts were up-regulated than down-regulated, highlighting AR's role as a transcriptional repressor in the testis. Twelve transcripts were uniquely affected, and 16 transcripts were more severely affected in Sertoli cell-specific Ar ablation compared with hypomorphic Ar mutants. Using a comparative genomic approach, we analyzed the 6 kb around the transcriptional start sites of affected transcripts for conserved AREs (androgen response elements). We identified at least one conserved ARE in 65% of the genes misregulated in our microarray analysis where clear mouse-human orthologs were available. We used a reporter assay in cell culture to functionally verify the AREs for the kallikrein 27 gene. This suggests that the majority of the misregulated transcripts have a high probability of being direct AR targets. The transcripts affected by these Ar mutations encode a diverse array of proteins whose molecular functions support the contention that AR supports spermatogenesis in both a permissive and instructive fashion.

Estrogen-dependent expression of the tissue kallikrein gene (Klk1) in the mouse uterus and its implications for endometrial tissue growth

Tissue kallikrein mK1 is a serine protease involved in the generation of bioactive kinins for normal cardiac and arterial function in the mouse. In the present study, the tissue kallikrein gene Klk1, which codes for mK1, was shown to be one of the most prevalent of the Klk gene species in the uteri of adult mice, and its mRNA level was significantly higher at estrus than at diestrus. Klk1 mRNA expression was enhanced in the uteri of ovariectomized mice receiving estradiol-17beta treatment. Both endometrial epithelial and stromal cells isolated from the mice exhibited Klk1 expression at detectable levels when cultured in the presence of estradiol-17beta. mK1 was characterized using the recombinant active enzyme. mK1 had trypsin-like activity with a strong preference for Arg over Lys in the P1 position, and its activity was inhibited by typical serine protease inhibitors. Casein, gelatin, fibronectin, collagen type IV, and high-molecular-weight kininogen were degraded by mK1. The single-chain tissue-type plasminogen activator was converted to the two-chain form by mK1. In addition, mK1 degraded insulin-like growth factor binding protein-3. The present data suggest that mK1 may be implicated in the growth of uterine endometrial tissues during the proliferative phase.

Markers of prostate region-specific epithelial identity define anatomical locations in the mouse prostate that are molecularly similar to human prostate cancers

Although the basic functions of the prostate gland are conserved among mammals, its morphology varies greatly among species. Comparative studies between mouse and human are important because mice are widely used to study prostate cancer, a disease that occurs in a region-restricted manner within the human prostate. An informatics-based approach was used to identify prostate-specific human genes as candidate markers of region-specific identity that might distinguish prostatic ducts prone to prostate cancer from ducts that rarely give rise to cancer. Subsequent analysis of normal and cancerous human prostates demonstrated that the genes microseminoprotein-beta (MSMB) and transglutaminase 4 (TGM4) were expressed in distinct groups of ducts in the normal human prostate, and only MSMB was detected in areas of prostate cancer. The mouse orthologs of MSMB and TGM4 were then used for expression studies in mice along with the mouse ventrally expressed gene spermine binding protein (SBP). All three genes were informative markers of region-specific epithelial identity with distinct expression patterns that collectively accounted for all ducts in the mouse prostate. Together with the human data, this suggested that MSMB expression defines an anatomical domain in the mouse prostate that is molecularly most similar to human prostate cancers. Computer-assisted serial section reconstruction was used to visualize the complete expression domains for MSMB, SBP, and TGM4 in the mouse prostate. This showed that MSMB is expressed in prostatic ducts that comprise 21% of the mouse dorso-lateral prostate. Finally, the expression of MSMB, SBP, and TGM4 was evaluated in a mouse prostate cancer model created by the prostate epithelium-specific deletion of the tumor suppressor PTEN. MSMB and TGM4 were rapidly and dramatically down-regulated in response to PTEN deletion suggesting that this model of prostate cancer includes a more rapid de-differentiation of the prostatic epithelium than is observed in organ-confined human prostate cancers.

In silico identification and Bayesian phylogenetic analysis of multiple new mammalian kallikrein gene families

Kallikrein gene families have been identified previously in genomes of the human, the mouse, and the rat, and individual kallikrein-like genes have been found in many more species. This study presents the in silico identification of kallikrein gene families in the recently sequenced genomes of four additional mammalian species, the chimpanzee, the dog, the pig, and the opossum. Phylogenies were constructed with gene sequences from all seven mammalian families, using Bayesian analysis, which clarified the evolutionary relationships between these genes. Individual gene sequences, as well as concatenated constructs of multiple sequences, were used. Fifteen kallikrein genes were located in the chimpanzee (Pan troglodytes) genome, while only 14 were identified in the canine (Canis familiaris) genome as no orthologue to human KLK3 was found. Thirteen genes were identified from the pig (Sus scrofa) genome, which lacked homologues to KLK2 and KLK3, and 11 genes, orthologous to human KLK5 through KLK15, were found in the opossum (Monodelphis domestica) genome. No kallikrein genes were identified from the available genome sequences of the chicken (Gallus gallus) or African clawed frog (Xenopus tropicalis). Within the family of kallikreins several subfamilies were suggested by phylogenetic analysis. One consisted of KLK4, KLK5, and KLK14; another of KLK9, KLK11, and KLK15; a third of KLK10 and KLK12; a fourth of KLK6 and KLK13; and finally one of KLK8 and the classical kallikreins (KLK1, KLK2, and KLK3).

Proteinase-activated Receptors, Targets for Kallikrein Signaling

Serine proteinases like thrombin can signal to cells by the cleavage/activation of proteinase-activated receptors (PARs). Although thrombin is a recognized physiological activator of PAR(1) and PAR(4), the endogenous enzymes responsible for activating PAR(2) in settings other than the gastrointestinal system, where trypsin can activate PAR(2), are unknown. We tested the hypothesis that the human tissue kallikrein (hK) family of proteinases regulates PAR signaling by using the following: 1) a high pressure liquid chromatography (HPLC)-mass spectral analysis of the cleavage products yielded upon incubation of hK5, -6, and -14 with synthetic PAR N-terminal peptide sequences representing the cleavage/activation motifs of PAR(1), PAR(2), and PAR(4); 2) PAR-dependent calcium signaling responses in cells expressing PAR(1), PAR(2), and PAR(4) and in human platelets; 3) a vascular ring vasorelaxation assay; and 4) a PAR(4)-dependent rat and human platelet aggregation assay. We found that hK5, -6, and -14 all yielded PAR peptide cleavage sequences consistent with either receptor activation or inactivation/disarming. Furthermore, hK14 was able to activate PAR(1), PAR(2), and PAR(4) and to disarm/inhibit PAR(1). Although hK5 and -6 were also able to activate PAR(2), they failed to cause PAR(4)-dependent aggregation of rat and human platelets, although hK14 did. Furthermore, the relative potencies and maximum effects of hK14 and -6 to activate PAR(2)-mediated calcium signaling differed. Our data indicate that in physiological settings, hKs may represent important endogenous regulators of the PARs and that different hKs can have differential actions on PAR(1), PAR(2), and PAR(4).

1.70 A X-ray structure of human apo kallikrein 1: structural changes upon peptide inhibitor/substrate binding

Human kallikreins are serine proteases that comprise a recently identified large and closely related 15-member family. The kallikreins include both regulatory- and degradative-type proteases, impacting a variety of physiological processes including regulation of blood pressure, neuronal health, and the inflammatory response. While the function of the majority of the kallikreins remains to be elucidated, two members are useful biomarkers for prostate cancer and several others are potentially useful biomarkers for breast cancer, Alzheimer's, and Parkinson's disease. Human tissue kallikrein (human K1) is the best functionally characterized member of this family, and is known to play an important role in blood pressure regulation. As part of this function, human K1 exhibits unique dual-substrate specificity in hydrolyzing low molecular weight kininogen between both Arg-Ser and Met-Lys sequences. We report the X-ray crystal structure of mature, active recombinant human apo K1 at 1.70 A resolution. The active site exhibits structural features intermediate between that of apo and pro forms of known kallikrein structures. The S2 to S2' pockets demonstrate a variety of conformational changes in comparison to the porcine homolog of K1 in complex with peptide inhibitors, including the displacement of an extensive solvent network. These results indicate that the binding of a peptide substrate contributes to a structural rearrangement of the active-site Ser 195 resulting in a catalytically competent juxtaposition with the active-site His 57. The solvent networks within the S1 and S1' pockets suggest how the Arg-Ser and Met-Lys dual substrate specificity of human K1 is accommodated.

Role of p90 ribosomal S6 kinase-mediated prorenin-converting enzyme in ischemic and diabetic myocardium

BACKGROUND

Epidemiological data strongly indicate that diabetes increases the incidence of heart failure. Although the benefit of angiotensin-converting enzyme inhibitor (ACE-I) treatment during and after myocardial infarction has been found to be greater in diabetics than nondiabetics and activation of the renin-angiotensin system (RAS) has been implicated, the molecular basis of these actions remains unclear.

METHODS AND RESULTS

We generated transgenic mice with cardiac-specific overexpression of wild-type p90 ribosomal S6 kinase (WT-p90RSK-Tg) and a dominant-negative form of p90RSK (DN-p90RSK-Tg). Recovery of cardiac function after ischemia/reperfusion in WT-p90RSK-Tg isolated mouse hearts was significantly impaired. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry revealed specific induction of prorenin-converting enzyme (PRECE) in WT-p90RSK-Tg mice. mRNA induction of PRECE was confirmed with serial angiotensinogen protein reduction after perfusion in WT-p90RSK-Tg mice, suggesting an increase of angiotensinogen cleavage and subsequent RAS activation in WT-p90RSK-Tg mice. We investigated the role of the RAS in WT-p90RSK-Tg animals after ischemia/reperfusion with the use of an ACE-I (captopril) and an angiotensin II type 1 receptor blocker (olmesartan). We did not observe any effect of these inhibitors in non-Tg littermate controls, thus corroborating other reports in rodents. In contrast, both captopril and olmesartan significantly improved cardiac function and reduced infarct size in WT-p90RSK-Tg mice. At 8 months of age, WT-p90RSK-Tg mice developed cardiac dysfunction. p90RSK activity and PRECE mRNA were both increased by streptozotocin-induced hyperglycemia in non-Tg littermate controls, whereas DN-p90RSK-Tg animals exposed to streptozotocin did not have PRECE induction.

CONCLUSIONS

This study demonstrates the critical role of p90RSK in hyperglycemia-mediated myocardial PRECE induction, which may explain the augmentation of the RAS in diabetic hearts and provide an alternative therapeutic approach to treat diabetic cardiomyopathy.

Evolution of kallikrein-related peptidases in mammals and identification of a genetic locus encoding potential regulatory inhibitors

The human kallikrein locus on chromosome 19 consists of 15 genes encoding serine proteases. Here we review studies on their evolution, which demonstrate that there are several taxon-unique KLK1 paralogs in mouse, rat and horse, but not in primates and many other mammals. Furthermore, the duplication yielding KLK2 and prostate-specific antigen (KLK3) appears to be specific to primates, but a functional progenitor to KLK2 is expressed in the dog prostate. The linkage to a locus of possible regulatory protease inhibitors on chromosome 20 is discussed, as is the potential role of the kallikrein locus in innate immunity.

A comprehensive nomenclature for serine proteases with homology to tissue kallikreins

The human kallikrein locus on chromosome 19q13.3-13.4 contains kallikrein 1--the tissue kallikrein--and 14 related serine proteases. Recent investigations into their function and evolution have indicated that the present nomenclature for these proteins is inadequate or insufficient. Here we present a new nomenclature in which proteins without proven kininogenase activity are denoted kallikrein-related peptidase. Names are also given to the unique rodent proteins that are closely related to kallikrein 1.

Involvement of neuropsin in the pathogenesis of experimental autoimmune encephalomyelitis

Inflammation, demyelination, and axonal damage of the central nervous system (CNS) are major pathological features of multiple sclerosis (MS). Proteolytic digestion of the blood-brain barrier and myelin protein by serine proteases is known to contribute to the development and progression of MS. Neuropsin, a serine protease, has a role in neuronal plasticity, and its expression has been shown to be upregulated in response to injury to the CNS. To determine the possible involvement of neuropsin in demyelinating diseases of the CNS, we examined its expression in myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), a recognized animal model for MS. Neuropsin mRNA expression was induced in the spinal cord white matter of mice with EAE. Combined in situ hybridization and immunohistochemistry demonstrated that most of the cells expressing neuropsin mRNA showed immunoreactivity for CNPase, a cell-specific marker for oligodendrocytes. Mice lacking neuropsin (neuropsin-/-) exhibited an altered EAE progression characterized by delayed onset and progression of clinical symptoms as compared to wild-type mice. Neuropsin-/- mice also showed attenuated demyelination and delayed oligodendroglial death early during the course of EAE. These observations suggest that neuropsin is involved in the pathogenesis of EAE mediated by demyelination and oligodendroglial death.

Characterization of mouse glandular kallikrein 24 expressed in testicular Leydig cells

Mouse kallikrein 24 is thought to encode a functional serine protease belonging to the mouse glandular kallikrein gene family. Preliminary results suggest that this kallikrein may play a role in testis function in adult mice. In order to obtain insights into its physiological functions, we undertook molecular and biochemical analyses of this enzyme. We cloned a cDNA for kallikrein 24 from the adult mouse testis cDNA library. Kallikrein 24 was expressed in the kidney, submandibular glands, ovary, epididymis, and testis of the mouse. In the testis, kallikrein 24 mRNA was detectable at 4 weeks of postnatal development, and became more prominent thereafter. The kallikrein 24 gene was expressed exclusively in the Leydig cells of adult mice. When Leydig cells isolated from a 2-week-old mouse testis were cultured in the presence of testosterone, kallikrein 24 expression was induced. Active recombinant enzyme showed trypsin-like specificity, favorably cleaving Arg-X bonds of synthetic peptide substrates. The enzymatic activity was strongly inhibited by typical serine protease inhibitors. Mouse kallikrein 24 degraded casein, gelatin, fibronectin and laminin. These results suggest that the enzyme may play a role in the degradation of extracellular matrix proteins in the interstitial area surrounding the Leydig cells of the adult mouse testis. The present findings should contribute to future physiological studies of this mouse testis protease.

Identification of new splice variants and differential expression of the human kallikrein 10 gene, a candidate cancer biomarker

The human kallikrein gene 10 (KLK10) is a member of the kallikrein gene family on chromosome 19q13.4. This gene was identified by its downregulation in breast cancer, and preliminary evidence suggests that it may act as a tumor suppressor. A computer-based analysis was performed on EST and SAGE clones from the Cancer Genome Anatomy Project and other databases. Experimental verification of differential expression of KLK10 in cancer was performed by PCR using gene-specific primers. The mRNA and EST analysis allowed the construction of the longest transcript of the gene and characterization of a 5' extension of the reported mRNA. In addition, seven new splice variants of KLK10 were identified. One of these variants, named KLK10 splice variant 3 (KLK10-SV3) which starts with a novel first exon, was experimentally verified. This variant is predicted to encode for the same protein as the 'classical' KLK10 mRNA, since the first exon is untranslated. One variant mRNA partially matches with the sequence of KLK10, while the rest of the mRNA matches with a portion of the polycystic kidney disease gene, found on chromosome 15. This variant could not be experimentally verified in either normal or cancerous tissues. There are 39 reported single nucleotide polymorphisms (SNPs) for the gene, in which three result in amino acid substitutions. SAGE analysis shows a clear upregulation of KLK10 in ovarian, pancreatic, colon, and gastric cancers. The gene is, however, downregulated in breast and prostate cancers. A three-fold decrease in expression levels was noted in actinic keratosis, compared to normal skin from the same patient. The differential regulation of KLK10 in ovarian and prostate cancers was experimentally verified by RT-PCR analysis. In addition, a significant number of clones were isolated from carcinomas of the head and neck. Fewer clones were found in carcinomas of the skin, brain and prostate. Orthologues were identified in three other species, with the highest degree of homology observed with the mouse and rat orthologues (42% in each). In conclusion new splice variants of the KLK10 gene were identified. These in silico analyses show a differential expression of the gene in various malignancies and provide the basis for directing experimental efforts to investigate the possible role of the gene as a cancer biomarker.

Human tissue kallikrein gene family: applications in cancer

Human tissue kallikrein genes, located on the long arm of chromosome 19, are a subgroup of the serine protease family of proteolytic enzymes. Initially thought to consist of three members, the human kallikrein locus has now been extended and includes 15 tandemly located genes. These genes, and their protein products, share a high degree of homology and are expressed in a wide array of tissues, mainly those that are under steroid hormone control. PSA (hK3) is one of the human kallikreins, and is the most useful tumor marker for prostate cancer screening, diagnosis, prognosis and monitoring. hK2, another prostate-specific kallikrein, has also been proposed as a complementary prostate cancer biomarker. In the past 5 years, the newly discovered kallikreins (KLK4-KLK15) have been associated with several types of cancer. For example, hK4, hK5, hK6, hK7, hK8, hK10, hK11, hK13 and hK14 are emerging biomarkers for ovarian, breast, prostate and testicular cancer. New evidence raises the possibility that some kallikreins are directly involved with cancer progression. We here review the evidence linking kallikreins and cancer and their applicability as novel biomarkers for cancer diagnosis and management.

Ejaculates from the common marmoset (Callithrix jacchus) contain semenogelin and beta-microseminoprotein but not prostate-specific antigen

Human seminal plasma contains high concentrations of prostatic acid phosphatase (PAP), prostate-specific antigen (PSA), beta-microseminoprotein (MSP), semenogelin I (SgI), and semenogelin II (SgII), whereas only PAP and MSP are present in rodents. In order to gain a better understanding of the evolution and function of semen proteins, we have studied ejaculates from the common marmoset (Callithrix jacchus)-a New World monkey. Semen samples were analyzed with SDS-PAGE, Western blotting, and isoelectric focusing. Under reducing conditions the dominating protein components appear as heterogeneous material of 55-70 kDa and distinct protein bands of 85, 17, 16, and 15 kDa. The heterogeneous material contains glycosylated material detected by an antiserum recognizing both human SgI and SgII. Southern blotting indicates that the common marmoset has genes for both SgI and SgII. There are several marmoset MSP genes, but the strong immunoreactivity against one 15 kDa semen component with pI 7.3 suggests preferential expression of one gene in the prostate. Expression of two other genes cannot be excluded as indicated by weak reaction to isoforms with pI 6.6 and 4.9. Unexpectedly, PSA was not detected by either immunological methods or activity measurements. This is in agreement with results from Southern blotting suggesting that the common marmoset might not have a PSA gene. Thus, in this study we have shown that semen coagulum proteins are present in marmoset seminal plasma, but the lack of PSA precludes a similar liquefaction as of human semen.

Efficient transfer of PSA and PSMA cDNAs into DCs generates antibody and T cell antitumor responses in vivo

Gene therapy for prostate cancer may be realized through transduction of whole genes, such as PSA or PSMA, into immunotherapeutic dendritic cells (DCs). An oncoretroviral vector encoding human PSMA and a bicistronic oncoretroviral vector encoding human PSA and cell surface CD25 cDNAs were constructed. Remarkably, transfer of PSA/CD25 or PSMA cDNA during murine hematopoietic cell differentiation into DCs occurred with approximately 80% efficiency. In vitro, transduced DCs retained allostimulatory function and primed syngeneic T cells for tumor antigen-specific IFN-gamma secretion. In test experiments designed to elucidate mechanisms in vivo, syngeneic recipients of transduced DCs had increased anti-human PSA antibody titers and tumor-specific CD8(+) T cell IFN-gamma secretion with no detectable immune response to CD25. Gene-modified DC recipients had increased protection from specific tumor challenge for at least 18 weeks post-vaccination. DC vaccination also protected both male and female recipients. Gene-modified DC vaccination mediated regression of established, specific gene-expressing, TRAMP-C1 prostate cancer cell tumors. These findings indicate that antibody and cellular responses generated through PSA and PSMA gene transfer into DC yielded protective immunity, thereby providing further preclinical support for the implementation of immuno-gene therapy approaches for prostate cancer.

The evolution of the glandular kallikrein locus: identification of orthologs and pseudogenes in the cotton-top tamarin

Comparisons of the glandular kallikreins loci in human, mouse and rat revealed remarkable differences. For example, the mouse and the rat lack the genes encoding prostate-specific antigen (PSA) and human glandular kallikrein 2 (hK2). In contrast, the intergenic region between KLK1 and KLK15 is devoid of genes and spans only 1.5 kb in humans, but encompasses 23 KLK1-like genes spanning 290 kb in the mouse. To further elucidate the evolution of glandular kallikrein genes, we investigated the structure and organization of these genes in the cotton-top tamarin (Saguinus oedipus), a New World monkey. We conclude that this species has no PSA gene. Moreover, the ortholog of the hK2 gene is a pseudogene, as it contains several mutations that preclude formation of a functional serine protease. The expression of this gene was probably silenced by a 15-bp deletion observed in an androgen response element in the upstream promoter region. Replacing the deleted base pairs in vitro with nucleotides from the human counterpart dramatically restored the transcriptional activity to a level that even surpassed that of the human ortholog. We also determined the nucleotide sequence of KLK15 and the intergenic region between this gene and KLK1 in the cotton-top tamarin. The region between KLK1 and KLK15 is conserved between the cotton-top tamarin and humans, and there are no signs of the extension seen in the mouse. KLK15 appeared to be functional, thus, we predict that it generates a protease with specificity similar to that of the human ortholog.

Autoimmunity against a tissue kallikrein in IQI/Jic Mice: a model for Sjogren's syndrome

We have recently characterized IQI/Jic mice as a model for Sjogren's syndrome (SS), a chronic autoimmune disease in humans. In SS, local lymphocytic infiltrations into salivary and lacrimal glands frequently develop to the involvement of systemic exocrine and nonexocrine organs, and the mechanism for progression of this disease remains obscure. Herein, we report identification of an autoantigen shared by various target organs in IQI/Jic mice. Polypeptides identified based on immunorecognition by autoantibodies in sera from IQI/Jic mice affected with autoimmune disease (>12 weeks of age) were tissue kallikrein (Klk)-1 and -13 and were cross-reactive to the autoantibodies. Interestingly, Klk-13, but not Klk-1, caused a proliferative response of splenic T cells from IQI/Jic mice from the age of 4 weeks onward. In addition, remarkably enhanced expression of Klk-13 was observed in the salivary glands of the mice in accordance with the development of inflammatory lesions. These results indicate that Klk-13 acts as an autoantigen and may increase T cells responsive to organs commonly expressing Klk-13, playing a pivotal role in the etiology of progression of disease in IQI/Jic mice. Our findings provide insights into the contributions of autoantigens shared by multiple organs in the progress of SS from an organ-specific to a systemic disorder.

Differences in substrate and inhibitor sequence specificity of human, mouse and rat tissue kallikreins

The kininogenase activities of mouse (mK1), rat (rK1) and human (hK1) tissue kallikreins were assayed with the bradykinin-containing synthetic peptides Abz-MTEMARRPPGFSPFRSVTVQNH2 (where Abz stands for o-aminobenzoyl) and Abz-MTSVIRRPPGFSPFRAPRV-NH2, which correspond to fragments Met374-Gln393 and Met375-Val393 of mouse and rat LMWKs (low-molecular-mass kininogens) with the addition of Abz. Bradykinin was released from these peptides by the mK1- and rK1-mediated hydrolysis of Arg-Arg and Arg-Ser (or Arg-Ala) peptide bonds. However, owing to preferential hydrolysis of Phe-Arg compared with the Arg-Ala bond in the peptide derived from rat LMWK, hK1 released bradykinin only from the mouse LMWK fragment and preferentially released des-[Arg9]bradykinin from the rat LMWK fragment (Abz-MTSVIRRPPGFSPFRAPRV-NH2). The formation of these hydrolysis products was examined in more detail by determining the kinetic parameters for the hydrolysis of synthetic, internally quenched fluorescent peptides containing six N- or C-terminal amino acids of bradykinin added to the five downstream or upstream residues of mouse and rat kininogens respectively. One of these peptides, Abz-GFSPFRAPRVQ-EDDnp (where EDDnp stands for ethylenediamine 2,4-dinitrophenyl), was preferentially hydrolysed at the Phe-Arg bond, confirming the potential des-[Arg9]bradykinin-releasing activity of hK1 on rat kininogen. The proline residue that is two residues upstream of bradykinin in rat kininogen is, in part, responsible for this pattern of hydrolysis, since the peptide Abz-GFSPFRASRVQ-EDDnp was preferentially cleaved at the Arg-Ala bond by hK1. Since this peptidase accepts the arginine or phenylalanine residue at its S1 subsite, this preference seems to be determined by the prime site of the substrates. These findings also suggested that the effects observed in rats overexpressing hK1 should consider the activation of B1 receptors by des-[Arg9]bradykinin. For further comparison, two short internally quenched fluorescent peptides that bind to hK1 with affinity in the nM range and some inhibitors described previously for hK1 were also assayed with mK1 and rK1.

Cloning of a kallikrein pseudogene

OBJECTIVES

Kallikreins are a group of serine proteases clustered together on a small region of chromosome 19q13.4. Recent reports suggest that kallikreins are differentially expressed in malignancy and have potential as cancer biomarkers. The human kallikrein gene locus has now been fully characterized and 15 functional kallikreins were identified. Although many kallikrein pseudogenes have already been characterized in rodents, none have been identified in humans.

METHODS AND RESULTS

In the current study, we identified the first human kallikrein pseudogene named PsiKLK1 and mapped it between the KLK2 and KLK4 genes. This pseudogene shares a moderate degree of similarity with the adjacent functional kallikreins. It has a conserved histidine residue of the catalytic triad of serine proteases and its surrounding motif, but lacks the aspartate and serine residues. Positions of some cysteine residues are also conserved in the pseudogene. This pseudogene lacks intronic sequences and should thus be classified as a processed pseudogene. EST and PCR analyses indicate that this pseudogene may be transcriptionally active, because mRNA was detected in many tissues including the prostate, testis, pituitary, and adrenal glands, as well as in tissues of the female genital organs.

DISCUSSION

The mRNA sequence of the gene is, however, defective and is not predicted to code for a protein. Highly conserved sequences were found in the flanking region of the pseudogene, thus supporting the view that it evolved by retrotransposition. We also identified another serine protease fragment that has only the conserved histidine residue. The functional significance of the pseudogene and the other fragment is yet to be identified.

Taxon-specific evolution of glandular kallikrein genes and identification of a progenitor of prostate-specific antigen

In a previous study we demonstrated that repeated duplications of the tissue kallikrein gene (Klk1) had resulted in 24 paralogs in mouse. Here we demonstrate a different evolution of rat glandular kallikrein genes. Repeated duplications of an approximately 30-kb region, encompassing Klk1, Klk15, and Klk2-ps, resulted in 10 copies of each gene, but only the Klk1 paralogs are functional. The number of genes varies also between nonrodent mammals, e.g., there are probably no paralogs to KLK1 in cow and pig, whereas horse could have up to 5. In the dog, the gene encoding the prostatic arginine esterase was identified as an ortholog to the progenitor of the PSA and hK2 genes, and it carries the same conserved androgen-responsive elements directing prostate transcription as these genes. This is highly interesting with respect to animal models of benign prostate hyperplasia and prostate adenocarcinoma--diseases that have been described only in humans and dogs.

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 update on human and mouse glandular kallikreins

Human glandular kallikreins are secreted serine proteases, involved in many biological processes. Recently, the complete organization of the human and mouse genomic loci has been elucidated. These loci harbor the largest clusters of serine proteases within the human and mouse genomes. Mouse orthologs to all human kallikrein genes, except for KLK2 and KLK3 genes, have now been identified. Here, we describe an update of the genomic organization of these families in human and mouse, and provide some thoughts for future research directions.

A genomic analysis of rat proteases and protease inhibitors

Proteases perform important roles in multiple biological and pathological processes. The availability of the rat genome sequence has facilitated the analysis of the complete protease repertoire or degradome of this model organism. The rat degradome consists of at least 626 proteases and homologs, which are distributed into 24 aspartic, 160 cysteine, 192 metallo, 221 serine, and 29 threonine proteases. This distribution is similar to that of the mouse degradome but is more complex than that of the human degradome composed of 561 proteases and homologs. This increased complexity of rat proteases mainly derives from the expansion of several families, including placental cathepsins, testases, kallikreins, and hematopoietic serine proteases, involved in reproductive or immunological functions. These protease families have also evolved differently in rat and mouse and may contribute to explain some functional differences between these closely related species. Likewise, genomic analysis of rat protease inhibitors has shown some differences with mouse protease inhibitors and the expansion of families of cysteine and serine protease inhibitors in rodents with respect to human. These comparative analyses may provide new views on the functional diversity of proteases and inhibitors and contribute to the development of innovative strategies for treating proteolysis diseases.

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.

Human and mouse proteases: a comparative genomic approach

The availability of the human and mouse genome sequences has allowed the identification and comparison of their respective degradomes--the complete repertoire of proteases that are produced by these organisms. Because of the essential roles of proteolytic enzymes in the control of cell behaviour, survival and death, degradome analysis provides a useful framework for the global exploration of these protease-mediated functions in normal and pathological conditions.