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

Gallium Nanoparticle-Mediated Reduction of Brain Specific Serine Protease-4 in an Experimental Metastatic Cancer Model

Purpose:

Tumor growth and metastasis depend on angiogenesis; therefore, efforts are being made to develop specific angiogenic inhibitors. Gallium (Ga) is the second most common metal ion, after platinum, used in cancer treatment. Its activities are numerous and various. In the present study, we aimed to investigate the effect of Ga on brain metastasis arising from hepatocellular carcinoma (HCC).

Materials and methods:

Forty experimental rats (divided into 4 groups) received diethylnitrosamine (DEN) at a dose (20 mg/kg.b.wt.; for 6 weeks) to induce HCC and were treated with Ga nanoparticles (GaNPs) with the bacterium Bacillus licheniformis (1mg/kg.b.wt.). Liver functions (alanine aminotransferase; (ALT), aspartate aminotransferase; (AST) and gamma glutamyl transferase; (GGT) and alpha-fetoprotein (AFP)) were assessed with histopathological examination of liver sections to confirm the induction of HCC. In addtion, brain-specific serine protease 4 (BSSP4), extracellular signal-regulated kinase (ERK), a microtubule-associated protein (Tau), vascular endothelial growth factor (VEGF), vascular cells adhesion molecule-1 (VCAM-1), cytochrome P450 (CYP450), lipid peroxidation (MDA) and glutathione-S-transferase (GST) were measured in brain tissue.

Results:

GaNPs ranged from 5 to 7 nm. HCC was confirmed by elevation in liver enzymes and AFP. Additionally, histopathological examination of liver showed focal area of anaplastic hepatocytes with other cells forming acini associated with fibroblastic cell proliferation. In brain, compared to the DEN alone group, we found that GaNPs modulated brain metastasis by reducing CYP450 and BSSP4 mRNA, and protein expression of p-ERK and p-Tau, and angiogenesis mediators (VEGF and VCAM-1). Also, GaNPs elevated lipid peroxidation and GST activity.

Conclusion:

It is concluded that GaNPs may prevent metastasis via inhibition of BSSP4 mRNA expression leading to suppression of a variety of growth factors and cell adhesion molecules involved in tumor growth and angiogenesis.

Discovering sparse transcription factor codes for cell states and state transitions during development

Computational analysis of gene expression to determine both the sequence of lineage choices made by multipotent cells and to identify the genes influencing these decisions is challenging. Here we discover a pattern in the expression levels of a sparse subset of genes among cell types in B- and T-cell developmental lineages that correlates with developmental topologies. We develop a statistical framework using this pattern to simultaneously infer lineage transitions and the genes that determine these relationships. We use this technique to reconstruct the early hematopoietic and intestinal developmental trees. We extend this framework to analyze single-cell RNA-seq data from early human cortical development, inferring a neocortical-hindbrain split in early progenitor cells and the key genes that could control this lineage decision. Our work allows us to simultaneously infer both the identity and lineage of cell types as well as a small set of key genes whose expression patterns reflect these relationships.

The physiology and pathobiology of human kallikrein-related peptidase 6 (KLK6)

The human kallikrein-related peptidase 6 (KLK6) gene belongs to the 15-member kallikrein (KLK) gene family mapping to chromosome 19q13.3-13.4. Encoding for an enzyme with trypsin-like properties, KLK6 can degrade components of the extracellular matrix. The successful utilisation of another KLK member (KLK3/PSA) for prostate cancer diagnosis has led many to evaluate KLK6 as a potential biomarker for other cancer and diseased states. The observed dysregulated expression in cancers, neurodegenerative diseases and skin conditions has led to the discovery that KLK6 participates in other cellular pathways including inflammation, receptor activation and regulation of apoptosis. Moreover, the improvements in high-throughput genomics have not only enabled the identification of sequence polymorphisms, but of transcript variants, whose functional significances have yet to be realised. This comprehensive review will summarise the current findings of KLK6 pathophysiology and discuss its potential as a viable biomarker.

The autolytic regulation of human kallikrein-related peptidase 6

Human kallikrein-related peptidase 6 (KLK6) is a member of the kallikrein family of serine-type proteases, characterized as an arginine-specific digestive-type protease capable of degrading a wide-variety of extracellular matrix proteins. KLK6 has been proposed to be a useful biomarker for breast and ovarian cancer prognosis, is abundantly expressed in the CNS and cerebrospinal fluid, and is intimately associated with regions of active inflammatory demyelination in multiple sclerosis (MS) lesions. Inhibition of KLK6 results in delayed onset and reduced severity of symptoms associated with experimental autoimmune encephalomyelitis, suggesting a key effector role for this protease in CNS inflammatory disease. KLK6 has been shown to autolytically cleave internally, leading to inactivation and suggesting a negative feedback inhibition control mechanism. Alternatively, the ability of KLK6 to self-activate has also been reported, suggesting a positive feedback activation loop control mechanism. Activation of pro-KLK6 requires hydrolysis after a Lys residue; however, KLK6 exhibits 2 order of magnitude reduced affinity for hydrolysis after Lys versus Arg residues; therefore, the ability to autolytically activate has been called into question. In the present study the catalytic activity of KLK6 toward its pro-sequence and internal autolytic sequence is characterized. The results show that the ability of KLK6 to activate pro-KLK6 is essentially negligible when compared to the rate of the internal autolytic inactivation or to the ability of other proteases to activate pro-KLK6. The results thus show that the primary autolytic regulatory mechanism of KLK6 is negative feedback inhibition, and activation is likely achieved through the action of a separate protease.

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.

Kallikrein 8 is involved in skin desquamation in cooperation with other kallikreins

Kallikrein type serine proteases, KLK8/neuropsin, KLK6, and KLK7, have been implicated in the proliferation and differentiation of epidermal keratinocytes and in the pathogenesis of psoriasis. However, their mechanistic roles in these processes remain largely unknown. We applied 12-O-tetradecanoylphorbol-13-acetate on the wild type (WT) and the Klk8 gene-disrupted (Klk8(-/-)) mouse skin, inducing keratinocyte proliferation similar to the human psoriatic lesion. Klk8 mRNA as well as Klk6 and Klk7 mRNA were up-regulated after 12-O-tetradecanoylphorbol-13-acetate application in the WT mice. In contrast, Klk8(-/-) mice showed minimum increases of Klk6 and Klk7 transcripts, the proteins, and enzymatic activities. Relative to the WT, the Klk8(-/-) skin showed less proliferation and an increase in the number of cell layers in the stratum corneum. However, overexpression of Klk8 by adenovirus vector in knock-out keratinocytes did not result in an increase in Klk6 or Klk7 mRNA. The inefficient cleavage of adhesion molecules DSG1 and CDSN in Klk8(-/-) skin contributes to a delay in corneocyte shedding, resulting in the hyperkeratosis phenotype. We propose that in psoriatic lesion, KLK8 modulates hyperproliferation and prevents excessive hyperkeratosis by shedding the corneocytes.

Implications of protease M/neurosin in myelination during experimental demyelination and remyelination

Protease M/neurosin is a serine protease expressed by oligodendrocytes (OLGs) in the central nervous system (CNS). To investigate the role of protease M/neurosin during experimental demyelination and remyelination, mice were fed cuprizone (bis-cyclohexanon oxaldihydrazone). Semi-quantitative RT-PCR analysis and immunohistochemistry revealed that the expressions of protease M/neurosin mRNA and protein were rapidly reduced in demyelination, whereas the expression of protease M/neurosin was increased in pi form of glutathione-S-transferases (GST-pi)-positive OLGs during remyelination. Cultured primary OLGs displayed a strong correlation between protease M/neurosin and myelin basic protein (MBP). After tumor necrosis factor-alpha (TNF-alpha) and IFN-gamma stimulation, these proteins showed colocalization in the oligodendroglial process. The suppression of protease M/neurosin using RNAi reduced the level of MBP mRNA in cultured OLGs. In contrast, the reduced level of protease M/neurosin was not associated with oligodendroglial cell death or differentiation in cultured OLGs. This study identifies that protease M/neurosin in OLGs is closely associated with the expression of the MBP and the PLP gene. Our data emphasize that the maintenance of myelination is an important function of protease M/neurosin in OLGs, suggesting its relation to the oligodendroglial response to myelin disorders.

Divergence between motoneurons: gene expression profiling provides a molecular characterization of functionally discrete somatic and autonomic motoneurons

Studies in the developing spinal cord suggest that different motoneuron (MN) cell types express very different genetic programs, but the degree to which adult programs differ is unknown. To compare genetic programs between adult MN columnar cell types, we used laser capture microdissection (LCM) and Affymetrix microarrays to create expression profiles for three columnar cell types: lateral and medial MNs from lumbar segments and sympathetic preganglionic motoneurons located in the thoracic intermediolateral nucleus. A comparison of the three expression profiles indicated that approximately 7% (813/11,552) of the genes showed significant differences in their expression levels. The largest differences were observed between sympathetic preganglionic MNs and the lateral motor column, with 6% (706/11,552) of the genes being differentially expressed. Significant differences in expression were observed for 1.8% (207/11,552) of the genes when comparing sympathetic preganglionic MNs with the medial motor column. Lateral and medial MNs showed the least divergence, with 1.3% (150/11,552) of the genes being differentially expressed. These data indicate that the amount of divergence in expression profiles between identified columnar MNs does not strictly correlate with divergence of function as defined by innervation patterns (somatic/muscle vs. autonomic/viscera). Classification of the differentially expressed genes with regard to function showed that they underpin all fundamental cell systems and processes, although most differentially expressed genes encode proteins involved in signal transduction. Mining the expression profiles to examine transcription factors essential for MN development suggested that many of the same transcription factors participate in combinatorial codes in embryonic and adult neurons, but patterns of expression change significantly.

Expression of Myelencephalon-Specific Protease after Cryogenic Lesioning of the Rat Parietal Cortex

The gene for myelencephalon-specific protease (MSP) is a member of the kallikrein gene family and in rats is expressed mainly in the central nervous system. Its function and alteration in brain injury have not yet been clarified. We examined the expression of MSP after cryogenic injury (CI) using in situ hybridization, immunohistochemistry, and Western blotting. Analysis of MSP mRNA by in situ hybridization revealed a higher level of expression around the cryogenic area than on the contralateral side at 2-7 days after CI, with peak expression occurring 7 days after CI. Immunohistochemical analysis demonstrated expression of MSP protein at 1 day after CI, in the same region in which MSP mRNA was observed, with peak expression again at 7 days after CI, in the area around the lesion. Double immunohistochemical labeling revealed that MSP was expressed mainly in oligodendrocytes. These results suggest that expression of MSP may be related to the turnover of myelin-associated proteins and extracellular matrix proteins after CI. The regulation of active MSP may be important in the physiological or pathological changes involved in remyelination or demyelination.

Barx2 functions through distinct corepressor classes to regulate hair follicle remodeling

The hair-growth cycle, a complex biological system requiring coordinate alterations in gene expression and cellular behavior, provides a challenging model for investigating the interplay of specific transcriptional regulation events. Here we report that the Barx2 homeodomain factor serves as a regulator of hair follicle remodeling (catagen), and loss of Barx2 in mice causes a defect both in the initiation and progression of catagen, resulting in a protracted first catagen, and later, causing short hair in adult gene-deleted mice. Barx2 negatively regulates its own promoter, and our study highlights the role of Barx2 as a repressor in the skin that can, unexpectedly, functionally interact with two WD40-domain factors distantly related to the yeast corepressor Tup1. These two corepressors, transducin-like enhancer of split and transducin beta-like 1, function through distinct and independent interactions with Barx2 for the repression of gene targets, including the Barx2 gene itself, emphasizing the roles of complementary repression strategies in engrailed homology-1 motif-containing homeodomain factors. Together, our data suggest that the hair-remodeling defect of Barx2 mutant mice could be explained, in part, by failure to repress one or more critical target genes.

Differential expression of neuropsin and protease M/neurosin in oligodendrocytes after injury to the spinal cord

Neuropsin and protease M/neurosin are serine proteases expressed by neurons and glial cells, and serve a variety of functions in the central nervous system (CNS). The current study demonstrates changes in the expression of these proteases following hemisection of the mouse spinal cord. Within unlesioned spinal cord, neuropsin mRNA expression was occasionally observed in the gray but not white matter, while the level of protease M/neurosin mRNA was higher in the white matter. After injury to the spinal cord, neuropsin mRNA expression was induced in the white matter in the area immediately adjacent to the lesion, peaking at 4 days post-injury and disappearing by 14 days. Enhanced expression of protease M/neurosin mRNA was observed throughout the white and gray matter surrounding the lesion, peaking at 4 days and persisting for 14 days. Neuropsin mRNA was expressed predominantly by CNPase-positive oligodendrocytes. Furthermore, most of these cells were also associated with immunoreactivity for protease M/neurosin protein. Within unlesioned spinal cord, most protease M/neurosin mRNA-expressing cells were CNPase-positive oligodendrocytes, and a substantial fraction of these cells also showed immunoreactivity for NG2, a marker for oligodendrocyte progenitors. After injury, protease M/neurosin mRNA expression within NG2-positive cells was significantly decreased, while the constitutive expression in CNPase-positive oligodendrocytes appeared to be preserved. These findings suggest that each subpopulation of oligodendrocytes based on the expression of neuropsin and protease M/neurosin has different roles in the response of the spinal cord to injury as well as in normal homeostasis.

Distinct promoters regulate tissue-specific and differential expression of kallikrein 6 in CNS demyelinating disease

Kallikrein 6 is a serine protease expressed abundantly in normal adult human and rodent CNS, and therein is regulated by injury. In the case of CNS demyelinating disease, K6 expression in CNS occurs additionally in perivascular and parenchymal inflammatory cells suggesting a role in pathogenesis. Herein we describe two unique transcripts that occur within the human and mouse K6 genes that differ in their 5'-untranslated regions. These transcripts have identical translation initiation sites in exon 3, are expressed in a tissue-specific fashion and are differentially regulated in response to CNS injury. While the human and mouse 5'-transcripts differ in sequence they are identical in genomic organization and tissue-specific expression. The most 5'-transcript, designated transcript 1, includes exon 1-7, and was detectable in all CNS regions, but not in any non-CNS tissues examined (spleen, thymus, liver, kidney, pancreas, submandibular gland and peripheral nerve). In contrast, transcript 2 lacks exon 1, but contains a unique sequence at the 5'-end of exon 2, designated exon 2A. Transcript 2 was expressed both in CNS and in each peripheral tissue. In a murine model of human CNS demyelinating inflammatory disease induced by Theiler's picornovirus, mouse K6 transcript 1 was up-regulated in brain and spinal cord at acute and more chronic phases of CNS inflammation and demyelination, while overall transcript 2 expression was not significantly altered. However, in isolated splenocyte cultures, transcript 2 was up-regulated two-fold by cellular activation. Tissue-specific expression patterns and differential regulation in CNS disease indicates that each K6 5'-transcript is probably regulated by unique promoter elements and may serve as a molecular target to treat inflammatory demyelinating disease.

Granzyme N, a Novel Granzyme, Is Expressed in Spermatocytes and Spermatids of the Mouse Testis1

We cloned a cDNA for a novel granzyme, granzyme N (Gzmn), from a mouse testes cDNA library. The testes contained two distinct species of Gzmn mRNA, one of which codes for a complete protein of 248 amino acids with three essential residues required for catalytic activity. The Gzmn mRNA was specifically expressed in the testes of adult mice. The Gzmn expression was found to initiate in the testes at 3 wk of age and to become more prominent as the animal reached sexual maturity. In situ hybridization analysis revealed that both spermatocytes and spermatids of the adult mouse testes express Gzmn mRNA. Consistent with these findings, the protein was immunohistochemically detected in the spermatocytes and spermatids, although some of the germ cells showed no positive staining. Gzmn was demonstrated to be a secretory and N-glycosylated protein that exists in two protein forms in the testes extract. In the cryptorchid testes, the expression of Gzmn transcript was drastically reduced on Postoperative Day 10, whereas the protein level was gradually decreased starting on Day 6. The local heating (43 degrees C, 20 min) of the testes did not change the Gzmn expression level at either 8 or 16 h after treatment. These results suggest that Gzmn is not involved in the process of germ cell apoptosis induced by heat shock, but that it may be involved in spermatogenesis in the mouse testes.

Expression of myelencephalon-specific protease in transient middle cerebral artery occlusion model of rat brain

Myelencephalon-specific protease (MSP) is one of the serine proteases and is expressed in the central nervous system of rats. Its function and alternation in brain injury have not yet been clarified. In this study, we investigated the expression of MSP after transient middle cerebral artery occlusion (MCAO) using in situ hybridization and immunohistochemistry. In situ localization of MSP mRNA demonstrated a higher level in the corpus callosum and around the ischemic area from 12 h to 14 days after MCA reperfusion, with the peak of expression coming 3 days after reperfusion in both regions. Immunohistochemically, the expression of protein was found 1 day after reperfusion in the same brain region that was observed for mRNA. The peak was 7 days after reperfusion in both regions. Micro-autoradiography, immunostaining and double immunohistochemical labeling revealed the expression of MSP to be located mainly in the oligodendrocytes. The present results indicate that MSP may be related to the turnover of the myelin-associated proteins and the extracellular matrix proteins after transient MCAO. The activation of MSP may play a role in remodeling processes such as neurite outgrowth and remyelination.

Targeting kallikrein 6‐proteolysis attenuates CNS inflammatory disease

Kallikrein 6 (K6, MSP) is a newly identified member of the Kallikrein family of serine proteases that is preferentially expressed in the adult central nervous system (CNS). We have previously demonstrated that K6 is abundantly expressed by inflammatory cells at sites of CNS inflammation and demyelination in animal models of multiple sclerosis (MS) and in human MS lesions. To test the hypothesis that this novel enzyme is a mediator of pathogenesis in CNS inflammatory disease, we have evaluated whether autonomously generated K6 antibodies alter the clinicopathological course of disease in murine proteolipid protein139-151-induced experimental autoimmune encephalomyelitis (PLP139-151 EAE). We demonstrate that immunization of mice with recombinant K6 generates antibodies that block K6 enzymatic activity in vitro, including the breakdown of myelin basic protein (MBP), and that K6-immunized mice exhibit significantly delayed onset and severity of clinical deficits. Reduced clinical deficits were reflected in significantly less spinal cord pathology and meningeal inflammation and in reduced Th1 cellular responses in vivo and in vitro. These data demonstrate for the first time that K6 participates in enzymatic cascades mediating CNS inflammatory disease and that this unique enzyme may represent a novel therapeutic target for the treatment of progressive inflammatory disorders, including MS.

Role of kallikrein enzymes in the central nervous system

Kallikreins are a subgroup of the serine protease family of enzymes. Until recently, it was thought that the human kallikrein gene family includes only three members. Over the past 3 years, the human kallikrein gene locus on chromosome 19q13.4 has been characterized. This family includes 15 members for which new nomenclature has been established. A number of kallikreins are expressed in the central nervous system (CNS). Experimental evidence has shown that at least two kallikreins, KLK6 and KLK8, have potential functions in the CNS. KLK8 (neuropsin) is highly expressed in brain tissues and may play a role in brain development, plasticity and response to stress. Of particular interest is the possible involvement of kallikreins in the pathogenesis of Alzheimer's disease (AD). KLK6 (zyme/protease M/neurosin) seems to be down regulated in serum and tissues of Alzheimer's disease patients and may be involved in amyloid metabolism.

Decreased cerebrospinal fluid levels of neurosin (KLK6), an aging-related protease, as a possible new risk factor for Alzheimer's disease

Neurosin is a kallikrein-like serine protease expressed preferentially in the human brain. It is localized in senile plaques and neurofibrillary tangles in the brains of individuals with Alzheimer's disease (AD) and in Lewy bodies in patients with Parkinson's disease. Neurosin is present in the cerebrospinal fluid (CSF) as a proenzyme and does not show any enzymatic activity. We have developed a sandwich ELISA system using monoclonal and polyclonal antibodies against human neurosin and have measured neurosin levels in the CSF from AD and non-CNS disease patients. Both male and female patients with peripheral neuropathy showed statistically positive correlations between CSF neurosin concentrations and age (males, n = 52, r = 0.482, p < 0.005; females, n = 43, r = 0.365, p < 0.005). In contrast, such positive correlation was not observed in the CSF from patients with AD. Further, some such patients showed extremely low levels of CSF neurosin. Our results suggest that neurosin is an aging-related protease and that a decreased CSF concentration of neurosin may be a risk factor for developing AD.

Crystal structure and biochemical characterization of human kallikrein 6 reveals that a trypsin-like kallikrein is expressed in the central nervous system

The human kallikreins are a large multigene family of closely related serine-type proteases. In this regard, they are similar to the multigene kallikrein families characterized in mice and rats. There is a much more extensive body of knowledge regarding the function of mouse and rat kallikreins in comparison with the human kallikreins. Human kallikrein 6 has been proposed as the homologue to rat myelencephalon-specific protease, an arginine-specific degradative-type protease abundantly expressed in the central nervous system and implicated in demyelinating disease. We present the x-ray crystal structure of mature, active recombinant human kallikrein 6 at 1.75-A resolution. This high resolution model provides the first three-dimensional view of one of the human kallikreins and one of only a few structures of serine proteases predominantly expressed in the central nervous system. Enzymatic data are presented that support the identification of human kallikrein 6 as the functional homologue of rat myelencephalon-specific protease and are corroborated by a molecular phylogenetic analysis. Furthermore, the x-ray data provide support for the characterization of human kallikrein 6 as a degradative protease with structural features more similar to trypsin than the regulatory kallikreins.

Developmental changes and localization of mouse brain serine proteinase mRNA and protein in mouse brain

Serine proteases are known to be involved in neural development and various functions in the central nervous system. Mouse brain serine proteinase (mBSP) is expressed almost exclusively in the mouse brain and it has been characterized at the molecular and biochemical levels. In this study, we analyzed the developmental changes and localization of mBSP mRNA and protein in the mouse brain, using reverse transcription-polymerase chain reaction, Western blotting, and immunohistochemistry. Expression of mBSP was strong in the white matter and the nerve tracts after postnatal day 30, especially in the cerebellum and the medulla oblongata. These results suggest that mBSP contributes to development and sustaining the functions in the mouse brain.

Keratinocyte-specific onset of serine protease BSSP expression in experimental carcinogenesis

Malignant transformation of mouse skin by chemical carcinogens and tumor promoters, such as the phorbol ester 12-O-tetradecanoylphorbol-13-acetate, is a multistage process leading to the formation of squamous cell carcinomas. In an effort to identify target genes whose expression is associated with skin tumorigenesis we combined elements of suppression subtractive hybridization with differential screening to isolate genes that are differentially upregulated in mouse skin after short-term treatment with 12-O-tetradecanoylphorbol-13-acetate and that exhibit a high constitutive expression in squamous cell carcinomas. Here, we report the detailed analysis of one of these cDNAs encoding the serine protease BSSP in mouse skin. Phorbol ester application increases BSSP expression in keratinocytes of the epidermis and the hair follicle several-fold starting 4 h post- treatment. Transcriptional activation of BSSP by 12-O-tetradecanoylphorbol-13-acetate was found to be independent of c-Fos expression and resistant to downregulation by glucocorticoids. By monitoring BSSP expression throughout experimental skin carcinogenesis we found strong constitutive expression in hyperplastic epidermis as well as in proliferatively active keratinocytes of benign and malignant skin tumors. These results establish a novel link between expression of an as yet ill-defined serine protease and skin carcinogenesis.

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.