Molecular cloning of a novel trypsin-like serine protease (neurosin) preferentially expressed in brain

The effects of stimulating protease-activated receptor-1 and -2 in A172 human glioblastoma

Human glioblastoma cell line A172 expressed protease-activated receptor-1 and -2 (PAR-1 and PAR-2). We investigated the effects of the stimulation of these receptors by receptor-activating agonist peptides on the Ca2+ signaling, protein kinase C translocation, cell morphology and cell proliferation in A172. Both PAR-1 agonist SFLLRN and PAR-2 agonist SLIGKV induced an increase in [Ca2+]i. The prior treatment of A172 with PAR-2 agonist SLIGKV did not influence the [Ca2+]i response to PAR-1 agonist SFLLRN or thrombin, however, the prior treatment with PAR-1 agonist SFLLRN or thrombin completely abolished the second response to PAR-2 agonist SLIGKV. Treatment with each agonist peptide produced thinner and fewer processes in A172. The PAR-2 agonist inhibited the proliferation of A172 significantly while PAR-1 agonist did not. PKC-alpha and gamma were translocated from cytosol to membrane with either PAR-1 or PAR-2 stimulation, however, L was specifically translocated with SFLLRN, and lambda with SLIGKV, respectively. These results indicated that PAR-1 and PAR-2 stimulation produced a similar [Ca2+]i response and morphological changes in A172 glioblastoma while the effects on the cell proliferation and activation of PKC isozymes were distinct, suggesting that different signal transduction pathways were activated by these receptors. The uni-directional cross desensitization implies a functional linkage between PAR-1 and PAR-2 receptors.

Tissue-specific expression patterns and fine mapping of the human kallikrein (KLK) locus on proximal 19q13.4

The tissue or glandular kallikreins (KLK) are members of a highly conserved multigene family encoding serine proteases that are central to many biological processes. The rodent KLK families are large, highly conserved and clustered at one locus. The human KLK gene family is clustered on chromosome 19q13.3-13.4, and until recently consisted of just three members. However, recent studies have identified up to 11 new members of the KLK family that are less conserved than their rodent counterparts. Using a Southern blot and sequence analysis of 10 BACs and cosmids spanning approximately 400 kilobases (kb) either side of the original KLK 60-kb locus, we demonstrated that these genes also lie adjacent to this. We have also clarified the position of several microsatellite markers in relation to the extended KLK locus. Moreover, from Southern blot analysis of the cosmids and BACs with a degenerate oligonucleotide probe to the histidine-encoding region of serine proteases, we have shown that there are no other serine protease genes approximately 400 kb centromeric and 220 kb telomeric of the extended locus. We performed an extensive analysis of the expression patterns of these genes by poly(A)(+) RNA dot blot and reverse transcriptase-polymerase chain reaction analysis, and demonstrated a diverse pattern of expression. Of interest are clusters of genes with high prostate (KLK2-4) and pancreatic (KLK6-13) expression suggesting evolutionary conservation of elements conferring tissue specificity. From these findings, it is likely that the human KLK gene family consists of just 14 clustered genes within 300 kb and thus is of a comparable size to the rodent families (13-24 genes within 310 and 480 kb, respectively). In contrast to the rodent families, the newest members of the human KLK family are much less conserved in sequence (23-44% at the protein level) and appear to consist of at least four subfamilies. In addition, like the rat, these genes are expressed at varying levels in a diverse range of tissues although they exhibit quite distinct patterns of expression.

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.

cDNA cloning and tissue-specific splicing variants of mouse hippostasin/TLSP (PRSS20)

Two splicing variants of mouse hippostasin/TLSP (PRSS20) were identified and termed brain-type and prostate-type, respectively. Mouse hippostasin/TLSP showed 76.8% identity to the human homologue. Transient expression showed that both translational products were secreted into the conditioned medium. Mouse hippostasin/TLSP was expressed preferentially in the fetal brain and the prostate, but not in the neonatal brain. The brain expressed only brain-type hippostasin/TLSP, while the prostate expressed both types.

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.

Human kallikrein 6 (zyme/protease M/neurosin): a new serum biomarker of ovarian carcinoma

BACKGROUND

There is an urgent need for discovery and validation of new serum biomarkers for ovarian carcinoma. Early diagnosis of ovarian cancer with serologic analysis may improve clinical outcomes through administration of effective treatment. Human kallikrein 6 (hK6, encoded by the KLK6 gene) is a serine protease of the kallikrein gene family. Recently, we were able to develop an immunofluorometric procedure for the quantitative measurement of hK6 in biologic fluids, including serum.

METHODS

We have used an hK6-specific immunofluorometric assay to quantify hK6 protein in a large number of serum samples from normal individuals, as well as from patients with various malignancies.

RESULTS

We report for the first time, significant increase of serum hK6 concentration in a large proportion of patients with ovarian carcinoma. The elevations of hK6 appear to be relatively specific for ovarian cancer because other malignancies did not cause any increase in the concentration of this biomarker in serum. Serial hK6 measurements appear to correlate with CA125 levels in patients monitored postsurgery.

CONCLUSIONS

This is the first report describing significant elevations of hK6 concentration in serum of ovarian cancer patients. These data suggest that hK6 may represent a potential new biomarker for diagnosis and monitoring of ovarian carcinoma.

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 KLK7 (PRSS6) gene, encoding for the stratum corneum chymotryptic enzyme is a new member of the human kallikrein gene family - genomic characterization, mapping, tissue expression and hormonal regulation

The human stratum corneum chymotryptic enzyme (HSCCE; PRSS6, KLK7 gene) has been purified from human stratum corneum and is known to participate in the cell shedding process. The cDNA of the gene has previously been reported. Here, we describe the identification of 5' and 3' extensions of the published mRNA, and the complete genomic organization of the gene. KLK7 is composed of five coding exons which have similar lengths to exons of other kallikrein-like genes. The intron phases are completely conserved between this gene and other members of the kallikrein-like gene family. Precise mapping of KLK7 has indicated that it is located at chromosomal locus 19q13. 3-q13.4 between the already known genes zyme (KLK6) (centromere) and neuropsin (KLK8) (telomere). Until recently, it was thought that this gene is expressed only in the skin. We here provide evidence that KLK7 is also expressed at relatively high levels in the central nervous system, kidney, mammary and salivary glands. Its expression is up-regulated by estrogens and glucocorticoids in the breast carcinoma cell line BT-474. The cDNA and protein of this gene are homologous to sequences of other kallikrein-like genes. The gene encodes for a secreted protein. Phylogenetic analysis, the close structural similarities, and its co-localization in the same chromosomal region, suggest that the gene encoding for the stratum corneum chymotryptic enzyme is a new member of the expanded human kallikrein gene family.

Localization of a novel type trypsin-like serine protease, neurosin, in brain tissues of Alzheimer's disease and Parkinson's disease

Neurosin, a novel type of trypsin-like serine protease, has been shown to be preferentially expressed in human brain by northern blotting. We examined neurosin immunolabeling in the brains of neurologically normal persons and patients with Alzheimer's disease (AD) and with Parkinson's disease. We also identified the expression of the mRNA for neurosin by in situ hybridization histochemistry and reverse transcription-polymerase chain reaction (RT-PCR). The neurosin antibody stained all of the nuclei of various cell types. In neurons, there was also staining of neuronal cytoplasm, nucleoli and their processes. In AD, staining of neurons with processes was rare in the damaged areas. Some senile plaques, extracellular tangles and Lewy bodies were also positive for neurosin. Expression of the mRNA for neurosin was seen in neurons in the gray matter, and in microglial cells in the white matter. In AD, the intensity of the signal for neurosin mRNA in the gray matter was decreased compared with normal control brains. The relative levels of neurosin mRNA in AD brains, measured by RT-PCR, were lower than those in controls. These results suggest that in human brain neurosin plays various physiological roles, and that in AD this molecule, like other serine proteases, may have a role in the degradation of such substances as beta-amyloid protein.

Immunofluorometric assay of human kallikrein 6 (zyme/protease M/neurosin) and preliminary clinical applications

BACKGROUND

The human kallikrein gene family has contributed the best prostatic biomarkers currently available, including prostate-specific antigen (PSA) and human glandular kallikrein 2 (hK2). Recently, new members of the human kallikrein gene family have been identified. One new member is the KLK6 gene, encoding for human kallikrein 6 (hK6), which is also known as zyme/protease M/neurosin. In this paper, we describe development of antibodies and a sensitive immunofluorometric procedure for hK6 protein.

METHODS

Recombinant hK6 protein was used as immunogen to develop polyclonal antibodies in rabbits and mice. These antibodies were used to develop a sandwich-type time-resolved immunofluorometric procedure for hK6.

RESULTS

The newly developed hK6 immunofluorometric assay has a detection limit of 0.5 microg/L and upper concentration range of 200 microg/L. The assay is highly specific (no detectable cross-reactivity from PSA and hK2) and was used to quantify hK6 protein in various biologic fluids. Highest concentrations of hK6 were found in milk of lactating women, cerebral spinal fluid, nipple aspirate fluid, and breast cyst fluid. hK6 was also detected in male and female serum, in the majority of seminal plasmas and in a small fraction of amniotic fluids and breast tumor cytosols. hK6 was not detectable in urine. Chromatographic studies indicated that hK6 is present in these biologic fluids in its free, 30-kDa form.

CONCLUSIONS

This is the first reported sensitive immunofluorometric procedure for quantifying hK6 protein. hK6 is a secreted proteolytic enzyme that is found at high levels in cerebrospinal fluid and all breast secretions. This assay will facilitate further studies to examine the possible application of hK6 in diagnostics, including cancer and neurodegenerative disorders.

Synaptic microenvironments--structural plasticity, adhesion molecules, proteases and their inhibitors

Proteolytic regulation might be essential in neural plasticity in mature brain as well as the developing brain. An increasing number of studies support the idea that structural changes in the synapses are closely associated with synaptic plasticity. Proteases and their inhibitors in a synaptic microenvironment are important in the regulation of dynamic changes in the extracellular matrix components associated with synaptic plasticity. In the present article, the possible roles of neuronal proteases, protease inhibitors and extracellular macromolecules are reviewed.

A novel isoform of a kallikrein-like protease, TLSP/hippostasin, (PRSS20), is expressed in the human brain and prostate

cDNAs encoding two splicing variants of a serine protease, termed hippostasin, were isolated by a PCR-based cloning strategy. The difference of 5' nucleotide sequence resulted in the variation in the amino terminal ends of the two, brain and prostate, types of human hippostasin. The longest ORF of the brain-type was 250 amino acids with a putative signal peptide, while that of the prostate-type was 282 amino acids. Homology search using the amino acid sequence revealed that prostate-type hippostasin was identical to TLSP (PRSS20), which is expressed in human primary keratinocytes (1). Transient expression analysis showed that both brain- and prostate-type TLSP/hippostasin were secreted into the conditioned medium as about 40 kDa proteins. Human TLSP/hippostasin showed 47% and 45% identity to trypsinogen II and kallikrein, respectively. In fact, the recombinant human TLSP/hippostasin efficiently cleaved Bz-Phe-Arg-4-methylcoumaryl-7-amide, a kallikrein substrate, and weakly cleaved other substrates for kallikrein and trypsin. Northern blot analysis detected a 1.3 kb band in the whole brain and a 1.4 kb band in the prostate and the lung. In situ hybridization revealed that it was expressed preferentially by the pyramidal neurons in the human hippocampus and secretory epithelial cells in the prostate. These results indicated that TLSP/hippostasin is involved in the functions of the human central nervous system and prostate and that it is a multifunctional protease present in various organs.

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.

Molecular and biochemical characterization of a serine proteinase predominantly expressed in the medulla oblongata and cerebellar white matter of mouse brain

A full-length cDNA clone of a serine proteinase, mouse brain serine proteinase (mBSP), was isolated from a mouse brain cDNA library. mBSP, which has been recently reported to be expressed in the hair follicles of nude mice, is most similar (88% identical) in sequence to rat myelencephalon-specific protease. The mBSP mRNA was steadily expressed in the brain of adult mice with a transient expression in the early fetal stage during development. The genomic structure of the mouse gene for mBSP was determined. The gene, which is mapped to chromosome 7B4-B5, is about 7.4 kilobases in size and contains 7 exons. Interestingly, the 5'-untranslated region of the mBSP gene was interrupted by two introns. In situ hybridization analyses revealed that mBSP is expressed in the white matter of the cerebellum, medulla oblongata, and capsula interna and capsula interna pars retrolenticularis of mouse brain. Further, mBSP was immunolocalized to the neuroglial cells in the white matter of the cerebellum. Recombinant mBSP was produced in the bacterial expression system and activated by lysyl endopeptidase digestion, and the activated enzyme was purified for characterization. The enzyme showed amidolytic activities preferentially cleaving Arg-X bonds when 4-methylcoumaryl-7-amide-containing peptide substrates were used. Typical serine proteinase inhibitors, such as diisopropyl fluorophosphates, phenylmethanesulfonyl fluoride, soybean trypsin inhibitor, aprotinin, leupeptin, antipain, and benzamidine, strongly inhibited the enzyme activity. The recombinant mBSP effectively hydrolyzed fibronectin and gelatin, but not laminin, collagens I and IV, or elastin. These results suggest that mBSP plays an important role in association with the function of the adult mouse brain.

Purification and characterization of a trypsin-like serine proteinase from rat brain slices that degrades laminin and type IV collagen and stimulates protease-activated receptor-2

A trypsin-like serine proteinase was purified from the incubation medium of rat brain slices by gelatin zymography. The purification consisted of ammonium sulfate precipitation, benzamidine-Sepharose 6B affinity chromatography, and carboxymethyl-cellulose and gel filtration chromatographies. The gelatinolytic activity, identified at 22 kDa (P22) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing conditions, was eluted as one active peak throughout the purification, and the final preparation gave a single protein peak on reverse-phase HPLC. Diisopropyl fluorophosphate, benzamidine, p-toluenesulfonyl-L-lysine chloromethyl ketone, and aprotinin completely inhibited the activity of P22, whereas phenanthroline, p-toluene-sulfonyl-L-phenylalanine chloromethyl ketone, and elastinal did not. P22 efficiently digested the extracellular matrix proteins laminin and type IV collagen. P22 produced an increase in intracellular Ca2+ concentration in A172 glioblastoma, which was desensitized through prior stimulation with protease-activated receptor-2 agonist peptide SLIGKV, indicating that P22 can stimulate protease-activated receptor-2. Rat brain penetration injury induced gelatinolytic activity in the lesioned area whose molecular size was consistent with that of P22. These results indicated that on incubation of rat brain slices, a trypsin-like serine proteinase was secreted into the medium that was capable of digesting extracellular matrix and stimulating protease-activated receptor-2. It is suggested that the gelatinolytic activity induced by brain injury might be that of P22.

The new human kallikrein gene family: implications in carcinogenesis

The traditional human kallikrein gene family consists of three genes, namely KLK1 [encoding human kallikrein 1 (hK1) or pancreatic/renal kallikrein], KLK2 (encoding hK2, previously known as human glandular kallikrein 1) and KLK3 [encoding hK3 or prostate-specific antigen (PSA)]. KLK2 and KLK3 have important applications in prostate cancer diagnostics and, more recently, in breast cancer diagnostics. During the past two to three years, new putative members of the human kallikrein gene family have been identified, including the PRSSL1 gene [encoding normal epithelial cell-specific 1 gene (NES1)], the gene encoding zyme/protease M/neurosin, the gene encoding prostase/KLK-L1, and the genes encoding neuropsin, stratum corneum chymotryptic enzyme and trypsin-like serine protease. Another five putative kallikrein genes, provisionally named KLK-L2, KLK-L3, KLK-L4, KLK-L5 and KLK-L6, have also been identified. Many of the newly identified kallikrein-like genes are regulated by steroid hormones, and a few kallikreins (NES1, protease M, PSA) are known to be downregulated in breast and possibly other cancers. NES1 appears to be a novel breast cancer tumor suppressor protein and PSA a potent inhibitor of angiogenesis. This brief review summarizes recent developments and possible applications of the newly defined and expanded human kallikrein gene locus.

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.

Characterization of a recombinant soluble form of human placental leucine aminopeptidase/oxytocinase expressed in Chinese hamster ovary cells

Serum levels of human placental leucine aminopeptidase/oxytocinase (P-LAP) increase with gestation. cDNA cloning of P-LAP revealed that the enzyme is a type II membrane-bound protein containing the consensus HEXXH(X)18E motif found in the M1 family of zinc-metallopeptidase proteins. In this study, a recombinant soluble form of P-LAP found in maternal serum was expressed in Chinese hamster ovary cells, purified to homogeneity and then characterized. Although N-terminal sequencing revealed a four-amino-acid deletion, the purified enzyme was active and was shown to be a zinc-containing homodimeric protein with molecular mass of 280 kDa in solution. Using artificial substrates, it was shown that the enzyme has broad specificity and is inhibited by several compounds known as aminopeptidase inhibitors. Subsequently, sequential N-terminal amino-acid liberation of several peptide hormones by the enzyme was monitored and structures of the products were determined. Among the hormones having a cysteine residue at their N-terminal end and intramolecular disulfide bonds, it was found that vasopressin and oxytocin, but not calcitonin and endothelins, were cleaved by the enzyme. Because the molecular properties of oxytocinase so far reported often conflict, our results provide an initial biochemical and enzymatic characterization of moleculary defined P-LAP/oxytocinase.

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.

Protease M/neurosin mRNA is expressed in mature oligodendrocytes

No proteases have been identified to be oligodendrocyte-specific though there are phenomena in which proteases may be committed. We have cloned a cDNA for mouse homologue of protease M/neurosin, serine protease, and localized its mRNA in the mouse brain. The cDNA and the deduced amino acid sequences were 66% identical to those of human protease M/neurosin. In situ hybridization histochemistry revealed that the mRNA was localized in the mature oligodendrocytes which expressed proteolipid protein mRNA. Developmentally, protease M/neurosin mRNA was expressed by oligodendrocytes 2 to 7 days after the maturation. Thus, protease M/neurosin may be important to the processes occurring after the maturation of oligodendrocytes such as myelination or turnover of the proteins in the myelin.

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.

Enhanced hippocampal long-term potentiation and learning by increased neuronal expression of tissue-type plasminogen activator in transgenic mice

Adult cortical neurons can produce tissue-type plasminogen activator (tPA), an extracellular protease that plays a critical role in fibrinolysis and tissue remodelling processes. There is growing evidence that extracellular proteolysis may be involved in synaptic plasticity, axonal remodelling and neurotoxicity in the adult central nervous system. Here we show that transgenic mice overexpressing tPA in post-natal neurons have increased and prolonged hippocampal long-term potentiation (LTP), and improved performance in spatial orientation learning tasks. Extracellular proteolysis catalysed by tPA may facilitate synaptic micro-remodelling, and thereby play a role in activity-dependent neuronal plasticity and learning.

A novel form of human neuropsin, a brain-related serine protease, is generated by alternative splicing and is expressed preferentially in human adult brain

We have cloned cDNAs encoding two isoforms of a human novel serine protease. They encoded sequences of 260 and 305 amino acids, and both showed significant homology to mouse neuropsin. Mouse neuropsin has been reported to be involved in hippocampal plasticity, therefore we designated the proteins as type 1 and type 2 neuropsin, respectively. The amino acid sequences of the two types of human neuropsin were identical, except that type 2 carried an insert of 45 amino acids at the C-terminus of the leader sequence. The essential three amino acids in the active site triad, His, Asp, and Ser, and the single putative N-glycosylation site were conserved in human and mouse neuropsin. Sequence analysis of the 946 bp genomic DNA spanning the region encoding the insertion sequence revealed that two isoforms were generated in human brain by alternative splicing. However, the mouse genomic sequence did not conserve the 3' acceptor consensus sequence at the corresponding position, suggesting that type 2 neuropsin was a species-specific splice variant. When the open reading frames of human neuropsin were expressed in insect cells, both types of neuropsin were detected in the conditioned media by western blot analysis using anti-human neuropsin serum. Northern blot hybridization and reverse transcription-polymerase chain reaction showed predominant expression of type 1 neuropsin in pancreas. Type 2 neuropsin was preferentially expressed in human adult brain and hippocampus, although both types were expressed in fetal brain and placenta in comparable amounts. Dot blot hybridization showed that neuropsin was expressed in various regions of adult brain, including the hippocampus and cerebral cortex, and also in various fetal tissues. These results suggest that human type 2 neuropsin may be important to the adult brain plasticity, although both types may be necessary for the development of the nervous system.

Crystal structure of neuropsin, a hippocampal protease involved in kindling epileptogenesis

Neuropsin is a novel serine protease, the expression of which is highly localized in the limbic areas of the mouse brain and which is suggested to be involved in kindling epileptogenesis and hippocampal plasticity. The 2.1-A resolution crystal structure of neuropsin provides the first three-dimensional view of one of the serine proteases highly expressed in the nervous system, and reveals a serine protease fold that exhibits chimeric features between trypsin and nerve growth factor-gamma (NGFgamma), a member of the kallikrein family. Neuropsin possesses an N-glycosylated "kallikrein loop" but forms six disulfide bonds corresponding to those of trypsin. The ordered kallikrein loop projects proline toward the active site to restrict smaller residues or proline at the P2 position of substrates. Loop F, which participates in forming the S3/S4 sites, is similar to trypsin rather than NGFgamma. The unique conformations of loops G and H form an S1 pocket specific for both arginine and lysine. These characteristic loop structures forming the substrate-binding site suggest the novel substrate specificity of neuropsin and give a clue to the design of its specific inhibitors.

Cloning and tissue distribution of a novel serine protease esp-1 from human eosinophils

We have cloned a novel serine protease designated as esp-1 from human eosinophils. The amino acid sequence deduced from the cDNA showed that ESP-1 comprises a signal peptide of 18 amino acids, a propeptide of 23 amino acids, an active form sequence of 273 amino acids starting from an Ile-Val-Gly-Gly-Glu motif, the catalytic triad of serine proteases that has been characterized as the essential amino acid residues for the proteolytic activity, and a hydrophobic amino acid stretch in the carboxyl terminus, suggesting this enzyme is a novel membrane-type serine protease. The tissue distributions of esp-1 expression revealed that this protease is not only expressed in human eosinophils, but also widely expressed in mononuclear cells and various tissues other than skeletal muscle and kidney and is most abundant in testis and prostate, and moderately so in lung, spleen and pancreas.

The expression and localization of serine proteinase inhibitor PI-6 mRNA in developmental and ischemic mouse brain

A serine proteinase inhibitor, PI-6, is a member of the serine proteinase inhibitor (serpin) superfamily. In the present study, we investigated the developmental expression of PI-6 in the mouse brain and the effect of experimental ischemia on the expression of PI-6 in the adult brain. Northern blot analysis showed a high level of expression of PI-6 mRNA in brain stem and diencephalon as compared with other regions in the adult brain. The expression of PI-6 mRNA in the whole brain was increased gradually until 11 days after birth and was decreased again in the adult brain. In situ hybridization analysis revealed that the mRNA was localized in pyramidal cell layer of the post-natal hippocampus, especially in CA3 region, and in layer V of the cerebral cortex. In the brain stem, two specific motor nuclei, the facial nucleus and the motor nucleus of trigeminal nerve, which are important to active feeding, were strongly positive for PI-6 mRNA. Brain ischemia induced by bilateral ligation of the common carotid artery led to an increase in PI-6 mRNA expression in the whole brain, accompanied by the degeneration of hippocampal pyramidal cells. These results indicate distinct temporal and spatial expression of PI-6 in the mouse brain and suggest the involvement of PI-6 in the maturation of neurons and degenerative and regenerative processes.

Serine proteases in rodent hippocampus

Brain serine proteases are implicated in developmental processes, synaptic plasticity, and in disorders including Alzheimer's disease. The spectrum of the major enzymes expressed in brain has not been established previously. We now present a systematic study of the serine proteases expressed in adult rat and mouse hippocampus. Using a combination of techniques including polymerase chain reaction amplification and Northern blotting we show that tissue-type plasminogen activator (t-PA) is the major species represented. Unexpectedly, the next most abundant species were RNK-Met-1, a lymphocyte protease not reported previously in brain, and two new family members, BSP1 (brain serine protease 1) and BSP2. We report full-length sequences of the two new proteases; homologies indicate that these are of tryptic specificity. Although BSP2 is expressed in several brain regions, BSP1 expression is strikingly restricted to hippocampus. Other enzymes represented, but at lower levels, included elastase IV, proteinase 3, complement C2, chymotrypsin B, chymotrypsin-like protein, and Hageman factor. Although thrombin and urokinase-type plasminogen activator were not detected in the primary screen, low level expression was confirmed using specific polymerase chain reaction primers. In contrast, and despite robust expression of t-PA, the usual t-PA substrate plasminogen was not expressed at detectable levels.

Expression of trypsin by epithelial cells of various tissues, leukocytes, and neurons in human and mouse

It has long been believed that trypsin is normally synthesized only in the pancreas. In the present study, expression of trypsin in human and mouse nonpancreatic tissues was examined. Northern blot analysis of normal human tissues indicated that the trypsin gene is expressed at high levels in the pancreas and spleen and considerably in the small intestine. However, in situ hybridization and immunohistochemistry demonstrated that trypsin is widely expressed in epithelial cells of the skin, esophagus, stomach, small intestine, lung, kidney, liver, and extrahepatic bile duct, as well as splenic and neuronal cells. In the spleen, trypsin message was detected in macrophages, monocytes, and lymphocytes in the white pulp. In the brain, it was detected in the nerve cells of the hippocampus and cerebral cortex. Analysis by gelatin zymography confirmed the presence of a latent or an active form of trypsin in various normal mouse tissues. Reverse transcription-polymerase chain reaction analysis also confirmed the expression of trypsin genes in the spleen, liver, kidney, and brain of normal mice. Such a broad distribution of trypsin suggests its general roles in the maintenance of normal epithelial cell functions, the immune defense system, and the central nervous system.

The axonally secreted serine proteinase inhibitor, neuroserpin, inhibits plasminogen activators and plasmin but not thrombin

Neuroserpin is an axonally secreted serine proteinase inhibitor that is expressed in neurons during embryogenesis and in the adult nervous system. To identify target proteinases, we used a eucaryotic expression system based on the mouse myeloma cell line J558L and vectors including a promoter from an Ig-kappa-variable region, an Ig-kappa enhancer, and the exon encoding the Ig-kappa constant region (C kappa) and produced recombinant neuroserpin as a wild-type protein or as a fusion protein with C kappa. We investigated the capability of recombinant neuroserpin to form SDS-stable complexes with, and to reduce the amidolytic activity of, a variety of serine proteinases in vitro. Consistent with its primary structure at the reactive site, neuroserpin exhibited inhibitory activity against trypsin-like proteinases. Although neuroserpin bound and inactivated plasminogen activators and plasmin, no interaction was observed with thrombin. A reactive site mutant of neuroserpin neither formed complexes with nor inhibited the amidolytic activity of any of the tested proteinases. Kinetic analysis of the inhibitory activity revealed neuroserpin to be a slow binding inhibitor of plasminogen activators and plasmin. Thus, we postulate that neuroserpin could represent a regulatory element of extracellular proteolytic events in the nervous system mediated by plasminogen activators or plasmin.

cDNA cloning of a novel trypsin inhibitor with similarity to pathogenesis-related proteins, and its frequent expression in human brain cancer cells

A novel trypsin inhibitor (P25TI) with an apparent molecular size of 25 kDa has previously been purified from the culture medium of human glioblastoma cells. In this study, the cDNA encoding P25TI was isolated by the polymerase chain reaction (PCR) screening system, and its complete amino acid sequence was determined. The cDNA consisted of 1440 nucleotides and encoded a sequence of 258 amino acids. The deduced structure of P25TI seemed to consist of a putative signal peptide sequence (residues 1-25), a propeptide sequence (26-60) and a mature protein (residues 61-258). The P25TI sequence has no homology to other proteinase inhibitors, but has similarity to insect venom allergens, mammalian testis-specific proteins and plant pathogenesis-related proteins. P25TI mRNA was frequently expressed in human neuroblastoma and glioblastoma cell lines. Although Northern blotting analysis failed to detect P25TI mRNA in various human tissues, PCR analysis showed its expression in the brain, placenta and lymphocytes.

Molecular cloning of a novel brain-specific serine protease with a kringle-like structure and three scavenger receptor cysteine-rich motifs

In order to find serine proteases specifically expressed in brain, we designed degenerate mixed primers for consensus sequences of serine protease domains. By PCR utilizing the primers, we have cloned a novel sequence from reverse transcripts of total RNA of mouse brain and used it as a probe to screen a mouse brain cDNA library. Overlapping cDNAs encoding a precursor of a novel brain specific serine protease (BSSP-3) were cloned. DNA insert of the longest clone consisted of 2614-bp with an entire open reading frame encoding a secretory/membrane-anchored precursor protein consisting of 761 amino acids (AA) which may be processed to yield an active enzyme of 245 AA. As found in known serine proteases, BSSP-3 enzyme domain contained a catalytic triad which consists of AA residues essential for the enzyme activity. In the upstream region of the enzyme domain that resides at C-terminus of the precursor protein, there are, from N-terminus to downstream, a sequence similar to a kringle structure and three repetitive ones highly similar to the scavenger receptor cysteine-rich (SRCR) motifs. Northern blot analysis demonstrated that mBSSP-3 mRNA was specifically expressed in the mouse brain, lung and kidney. We concluded that a novel brain serine protease, BSSP-3, is a new member of kringle and SRCR superfamilies.