Molecular cloning, purification and in situ localization of human colon kallikrein

We have cloned and characterized a full-length cDNA encoding tissue kallikrein from a human colon carcinoma cell line (T84). The nucleic acid sequence of the colon kallikrein cDNA is identical to that of renal/pancreatic or tissue kallikrein cDNA. Reverse-transcription PCR followed by Southern-blot analysis using specific oligonucleotide probes showed expression of tissue kallikrein in human colon, pancreas and kidney. Tissue kallikrein mRNA was localized in glandular epithelial cells (goblet cells) in colon by in situ hybridization histochemistry. Human colon kallikrein was purified to apparent homogeneity by DEAE-Sepharose Cl-6B, aprotinin-affinity, and HQ/M perfusion chromatography. The purified colon kallikrein migrated as a broad, 40-45 kDa band in SDS/PAGE and was recognized by antibodies to human tissue kallikrein. The linear displacement curves for the colon kallikrein in an RIA were parallel with the human tissue kallikrein standard curve, indicating their immunological identity. The N-terminal sequence of the purified colon kallikrein matches completely with that of purified urinary or tissue kallikrein. These results indicate that human colon kallikrein is transcribed from the tissue kallikrein gene.

Muscle delivery of human kallikrein gene reduces blood pressure in hypertensive rats

We recently found that transgenic mice expressing human tissue kallikrein develop sustained hypotension. The result suggests that a continuous supply of human tissue kallikrein could have a prolonged effect on blood pressure reduction. In the present study, we investigated the potential of using human tissue kallikrein for gene therapy by injecting a kallikrein gene construct into the skeletal muscle of spontaneously hypertensive rats. Expression of the human tissue kallikrein messenger RNA in spontaneously hypertensive rats was identified by reverse transcription-polymerase chain reaction with Southern blot. Human tissue kallikrein was detected in the injected animals by an enzyme-linked immunosorbent assay. Injection of the human kallikrein gene into spontaneously hypertensive rats caused a significant reduction of systemic blood pressure, ranging from 15 to 26 mm Hg, compared with the control group. The differences were significant 1 week after the injection and continued for more than 2 months. Blood pressure reduction could be reversed after the administration of the bradykinin antagonist Hoe 140. The results indicate that somatic delivery of the human tissue kallikrein gene induces a sustained reduction of systemic blood pressure in spontaneously hypertensive rats. The present study raises the possibility of applying kallikrein gene therapy to the treatment of human hypertensive diseases.

Tacrolimus analysis: a comparison of different methods and matrices

We determined the through blood and plasma concentrations of tacrolimus from the day of transplantation through 30 days posttransplantation in four liver and four kidney transplant patients by three different methods. The first method involved a solid phase extraction of the blood or plasma using Sep-Pak columns (SPs) followed by quantitation of tacrolimus using an enzyme-linked immunosorbent assay (ELISA); the second method involved a liquid-liquid extraction using methylene chloride (MC) followed by quantitation of tacrolimus using the ELISA, and the third method involved a high-performance liquid chromatography (HPLC) fractionation of the extract obtained from the solid-phase extraction and quantitation of tacrolimus in the fractions by ELISA. The trough plasma tacrolimus concentrations ranged from 0.1 to 5.2 ng/ml. While the trough plasma concentrations of tacrolimus were similar and independent of the method of analysis in kidney transplant patients and in liver transplant patients with normal biochemical profile, in patients with liver dysfunction, tacrolimus plasma concentrations were higher when measured by SP-ELISA and MC-ELISA methods as compared to the HPLC-ELISA method. In plasma samples obtained from liver transplant patients with liver dysfunction, the presence of some metabolites that cross-reacted with the antibody used in the ELISA could be documented in the HPLC fraction corresponding to the metabolites. This indicates that while tacrolimus metabolites that cross-react significantly with the antibody used in the ELISA do not accumulate in kidney transplant patients, they can appear in the plasma of patients, they can appear in the plasma of patients with liver dysfunction. The trough blood tacrolimus concentrations in patients were significantly higher than the corresponding plasma concentrations and ranged from 1.4 to 107 ng/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Direct gene delivery of human tissue kallikrein reduces blood pressure in spontaneously hypertensive rats

Hypertension is a multigene and multifactorial disorder affecting approximately 25% of the population. To demonstrate potential therapeutic effects of human tissue kallikrein in hypertension, spontaneously hypertensive rats were subjected to somatic gene therapy. Two human tissue kallikrein DNA constructs, one under the promoter control of the metallothionein metal response element and the other under the control of the Rous sarcoma virus 3'-LTR, were generated. We delivered naked DNA constructs into spontaneously hypertensive rats via intravenous injection. The expression of human tissue kallikrein in rats was identified in the heart, lung, and kidney by reverse transcription polymerase chain reaction followed by Southern blot analysis and an ELISA specific for human tissue kallikrein. A single injection of both human kallikrein plasmid DNA constructs caused a sustained reduction of blood pressure which began 1 wk after injection and continued for 6 wk. A maximal effect of blood pressure reduction of 46 mmHg in rats was observed 2-3 wk after injection with kallikrein DNA as compared to rats with vector DNA (n = 6, P < 0.05). The hypotensive effect caused by somatic gene delivery of human tissue kallikrein in hypertensive rats is reversed by subcutaneous injection of aprotinin, a potent tissue kallikrein inhibitor. No antibodies to either human tissue kallikrein or kallikrein DNA were detected in rat sera after injection of the human kallikrein gene. These results show that direct gene delivery of human tissue kallikrein causes a sustained reduction in systolic blood pressure in genetically hypertensive rats and indicate that the feasibility of kallikrein gene therapy for treating human hypertension should be studied.

Intramuscular delivery of rat kallikrein-binding protein gene reverses hypotension in transgenic mice expressing human tissue kallikrein

The tissue kallikrein-kinin system has been postulated to play a role in blood pressure regulation. The activity of tissue kallikrein is controlled by a number of factors in vivo. Rat kallikrein-binding protein (RKBP) is a serine proteinase inhibitor which binds to and inhibits tissue kallikrein's activity in vitro. We have recently developed several hypotensive transgenic mouse lines which express human tissue kallikrein. In order to investigate the role of RKBP in blood pressure regulation, we delivered the RKBP to these transgenic mice by intramuscular injection. Expression of the RKBP was detected in skeletal muscle by reverse transcription-polymerase chain reaction and Southern blot analysis at 10, 20, 30, and 40 days post-injection. Immunoreactive RKBP levels in the muscle and serum of these mice were quantified by a RKBP-specific enzyme-linked immunosorbent assay and Western blot analysis. The levels of RKBP mRNA and immunoreactive protein were detectable at 10 days post-injection and increased significantly at 20 and 30 days. During this period, RKBP delivery significantly increased systemic blood pressure in the kallikrein transgenic mice to a level comparable to that of normotensive control mice. The RKBP and vector DNA delivery had no effect on the blood pressure of normotensive control mice. No serum antibodies to RKBP or its DNA were detected in the mice 40 days post injection. These results suggest that the increase of systemic blood pressure by RKBP delivery in these hypotensive transgenic mice may be mediated by inhibiting tissue kallikrein activity.

Cloning, sequence analysis and expression of the gene encoding the mouse bradykinin B2 receptor

The bradykinin B2 receptor (B2R) mediates most of the biological effects of kinins. In the present study, we have cloned and sequenced the gene (B2R) from a mouse embryonic stem (ES) cell genomic library. Mouse B2R is 7 kb in length containing three exons of 0.3, 0.23 and 3.7 kb separated by two introns of 2.5 and 0.41 kb. The first and second exons are noncoding while the third exon contains the full-length coding region and a long 3' noncoding region. An ATG translation start codon, TGA stop codon and a polyadenylation signal (AATAAA) were identified in the third exon. B2R encodes a protein of 41,470 Da and 366 amino acids (aa) forming seven transmembrane (TM) domains. At the aa level, B2R shares 91 and 82% sequence identity with the rat and human B2R, respectively. In the 5' flanking region, a consensus TATA box, a putative cAMP-response element, a putative phorbol ester-response element, a putative AP-1-binding site and a putative IL-6-response element were identified. Southern blot analysis following reverse transcription and PCR showed that B2R is expressed in most mouse tissues, except the liver and spleen, which is consistent with the wide distribution of B2R activity as deduced from pharmacological studies.

Detection of a kallikrein in the mouse lactating mammary gland: a possible processing enzyme for the epidermal growth factor precursor

Kallikreins are a multigene subfamily of serine proteases that may have a role in processing precursors of polypeptide hormones and growth factors. The epidermal growth factor (EGF) immunoreactivity in mouse milk is derived from the membrane-bound EGF precursor located on the lumenal border of the alveolar cells in the mammary gland. Release of EGF into the milk requires the hydrolysis of the EGF precursor at Arg-X cleavage sites. We report the presence of a candidate EGF precursor-processing enzyme in the lactating mouse mammary gland. Kallikrein transcripts in the mouse lactating mammary gland were detected by primer-directed enzyme amplification of complementary DNA (cDNA). Primers to selected conserved regions of the kallikrein cDNA resulted in an amplified product of the predicted size (573 basepairs). Sequence analysis of the product over three nonconserved regions identified mGK-6 (mouse renal kallikrein) as the primary kallikrein in BALB/c mouse lactating mammary gland. Transcription products for the EGF-binding protein (mGK-9), mGK-1, MGK-3, and mGK-4 were not detected by enzyme amplification with specific primers corresponding to these kallikrein cDNAs. Positive immunohistochemical staining of the apical membrane of mammary alveolar cells was detected with a polyclonal antiserum to mouse kallikrein. Incubation of cell membranes isolated from lactating mammary glands released soluble EGF-immunoreactive material. Aprotinin partially inhibited the release of this material, whereas other protease inhibitors, such as leupeptin, benzamidine, and limabean trypsin inhibitor, had no detectable effect. These results support the hypothesis that the release of EGF-immunoreactive material into the milk is in part dependent upon a kallikrein enzyme (mGK-6) in the BALB/c mouse lactating mammary gland.

Histopathology of lymphatic tissues in transgenic mice expressing human tissue kallikrein gene

BACKGROUND

Tissue kallikrein is a member of a family of closely related serine proteinases whose genetics are currently under intense investigation, but whose functions are still poorly understood. Functions of human tissue kallikrein, other than production of inflammatory kinins, are not readily amenable to investigation. A current mechanism for examining the function of a gene product is to introduce the gene with tissue-specific and/or inducible promoters into a suitable host that can then be experimentally manipulated.

EXPERIMENTAL DESIGN

Five transgenic mouse lines were established by backcross matings of transgenic founder mice containing the human tissue kallikrein gene. The inserted genomic material included the full-length kallikrein coding sequence as well as 800 bp in the upstream promoter region and 300 bp in the 3' noncoding region (PHK). Two of the five strains contained, in addition to the complete coding region and 3' flanking sequence, an upstream, zinc-inducible metallothionein promoter (MRE-PHK). Tissues from animals containing human kallikrein gene constructs (as determined by Southern blot of tail DNA) were examined histologically, and compared with control tissues from siblings negative for the gene.

RESULTS

Transgenic mice exhibited tissue pathology in several lymphatic organs. Cytoarchitecture was disrupted in both thymus and spleen. The distinction between cortex and medulla in the thymus was usually blurred, and cytolysis was common. Spleens exhibited decreased T cell-dependent zones (periarteriolar sheath), with active hematopoietic foci throughout the red pulp. In lymph nodes, cortical nodules were rare. The deep cortex (paracortical area) was usually normal in heterozygotes, but often depleted in homozygous animals. Comparable results were obtained in all five transgenic strains.

CONCLUSIONS

Expression of human tissue kallikrein appears to exert a profound effect on the cytoarchitecture of lymphatic tissues and a general decrease in lymphocytes, particularly in T cell-dependent areas. These findings presumably reflect altered function of lymphatic tissues in transgenic mouse strains carrying the human kallikrein gene.

Structure and chromosomal localization of the gene (BDKRB2) encoding human bradykinin B2 receptor

The bradykinin B2 receptor (BDKRB2) has high affinity for the intact kinins, which mediate a wide spectrum of biological effects, including pain, inflammation, vasodilation, and smooth muscle contraction and relaxation. In the present study, we have cloned and sequenced the gene encoding human bradykinin B2 receptor from a human genomic library. The B2 receptor gene contains three exons separated by two introns. The first and second exons are noncoding, while the third exon contains the full-length coding region, which encodes a protein of 364 amino acids forming 7 transmembrane domains. The human B2 gene shares high sequence identity with rat and mouse B2 receptor genes and significant similarity with the gene encoding the angiotensin II type I receptor in the nucleotide sequence and exon-intron arrangement. In the 5' flanking region, a consensus TATA box and several putative transcription factor-binding sites have been identified. Genomic Southern blot analysis showed that the B2 receptor is encoded by a single-copy gene that was localized to chromosome 14q32 by in situ hybridization. In a Southern blot analysis following reverse transcription and polymerase chain reaction, the human B2 receptor was found to be expressed in most human tissues.

Molecular cloning, sequence analysis, and chromosomal localization of the human protease inhibitor 4 (kallistatin) gene (PI4)

The gene encoding human protease inhibitor 4 (kallistatin; gene symbol PI4), a novel serine proteinase inhibitor (serpin), has been isolated and completely sequenced. The kallistatin gene is 9618 bp in length and contains five exons and four introns. The structure and organization of the kallistatin gene are similar to those of the genes encoding alpha 1-antichymotrypsin, protein C inhibitor, and alpha 1-antitrypsin. The kallistatin gene is also similar to the genes encoding rat and mouse kallikrein-binding proteins. The first exon of the kallistatin gene is a noncoding 89-bp fragment, as determined by primer extension. The fifth exon, which contains 308 bp of noncoding sequence, encodes the reactive center of kallistatin. In the 5'-flanking region of the kallistatin gene, 1125 bp have been sequenced and a consensus promoter segment with potential transcription regulatory sites, including CAAT and TATA boxes, an AP-2 binding site, a GC-rich region, a cAMP response element, and an AP-1 binding site, has been identified within this region. The kallistatin gene was localized by in situ hybridization to human chromosome 14q31-q32.1, close to the serpin genes encoding alpha 1-antichymotrypsin, protein C inhibitor, alpha 1-antitrypsin, and corticosteroid-binding globulin. In a genomic DNA Southern blot, kallistatin-related genes were identified in monkey, mouse, rat, bovine, dog, cat, and a ground mole. The patterns of hybridization revealed clues of human serpin evolution.

Molecular cloning and sequence analysis of rat bradykinin B2 receptor gene

The bradykinin B2 receptor mediates the effect of kinin. In order to understand the structure and regulation of its expression, we have cloned and sequenced the gene encoding the rat bradykinin B2 receptor and its 5' flanking region from a rat genomic library. The B2 receptor gene spans 7.3 kb in length and contains three exons which are separated by two introns. It encodes a peptide of 366 amino acids. The transcription initiation site was mapped by the primer extension assay. A variant TATA box sequence, an IL-6 response element and a cAMP response element were identified in the 5' flanking region of the rat bradykinin B2 receptor gene.

Directly labeled DNA probes using fluorescent nucleotides with different length linkers

Directly labeled fluorescent DNA probes have been made by nick translation and PCR using dUTP attached to the fluorescent label, Cy3, with different length linkers. With preparation of probes by PCR we find that linker length affects the efficiency of incorporation of Cy3-dUTP, the yield of labeled probe, and the signal intensity of labeled probes hybridized to chromosome target sequences. For nick translation and PCR, both the level of incorporation and the hybridization fluorescence signal increased in parallel when the length of the linker arm is increased. Under optimal conditions, PCR yielded more densely labeled probes, however, the yield of PCR labeled probe decreased with greater linear density of labeling. By using a Cy3-modified dUTP with the longest linker under optimal conditions it was possible to label up to 28% of the possible substitution sites on the target DNA with reasonable yield by PCR and 18% by nick translation. A mechanism involving steric interactions between the polymerase, cyanine-labeled sites on template and extending chains and the modified dUTP substrate is proposed to explain the inverse correlation between the labeling efficiency and the yield of DNA probe synthesis by PCR.

Cyanine dye dUTP analogs for enzymatic labeling of DNA probes

Fluorescence in situ hybridization (FISH) has become and indispensable tool in a variety of areas of research and clinical diagnostics. Many applications demand an approach for simultaneous detection of multiple target sequences that is rapid and simple, yet sensitive. In this work, we describe the synthesis of two new cyanine dye-labeled dUTP analogs, Cy3-dUTP and Cy5-dUTP. They are efficient substrates for DNA polymerases and can be incorporated into DNA probes by standard nick translation, random priming and polymerase chain reactions. Optimal labeling conditions have been identified which yield probes with 20-40 dyes per kilobase. The directly labeled DNA probes obtained with these analogs offer a simple approach for multicolor multisequence analysis that requires no secondary detection reagents and steps.

Family physicians' disagreements with the US Preventive Services Task Force recommendations

BACKGROUND

The 1989 recommendations of the US Preventive Services Task Force (USPSTF) represent an emerging consensus about which clinical preventive services should be delivered. However, practicing physicians disagree with a number of the recommendations in the Task Force prevention guidelines, and the reasons for disagreement have not been widely explored.

METHODS

A survey questionnaire assessing physician agreement or disagreement with the USPSTF recommendations was sent to all 1784 active members of the Ohio Academy of Family Physicians in October 1990. A factor analysis was performed on the items with which at least 5% of physicians disagreed. Associations of physician demographics and attitudes with the factor scores were then examined.

RESULTS

At least 5% of the 898 responding physicians disagreed with 67 of 150 USPSTF recommendations. Physicians disagreed with the USPSTF recommendations in three ways: (1) they believed that screening for some cancers is appropriate, even though not recommended by the USPSTF; (2) they believed that screening for other diseases in some populations is appropriate, even though not recommended by the USPSTF; and (3) they disagreed with some USPSTF recommendations for screening that is considered time-consuming or intrusive. Further analyses showed that practice setting and experience with the USPSTF guidelines were predictive of all three disagreement factors. Physician age, race, residency training, and reasons for disagreement were associated with two of the three factors.

CONCLUSIONS

Physician disagreement with the USPSTF recommendations was not random but clustered into three distinct factors. An opportunity exists to design educational interventions for targeted subgroups of physicians. The views of practicing physicians should be incorporated into future guidelines.

Molecular cloning and characterization of a novel kallikrein transcript in colon and its distribution in human tissues

1. We have cloned and characterized a new species of kallikrein cDNA from a human colon cDNA library. The new kallikrein cDNA clone contains a part of intron 2 of the tissue kallikrein gene which is spliced to the remaining exon sequences. It does not contain exons 1 and 2. 2. An in-frame open reading frame is present in the new kallikrein cDNA allowing translation of a 216-amino acid product. The intron-containing kallikrein transcript was detected in salivary glands, pancreas, kidney, colon, prostate gland, testis, spleen, and lung by reverse-transcription/polymerase chain reaction followed by Southern blot analysis using an intron-containing kallikrein-specific oligonucleotide probe. 3. The results indicate that the new species of kallikrein may be processed by alternative splicing or arises from a different transcription initiation site.

Prostasin is a novel human serine proteinase from seminal fluid. Purification, tissue distribution, and localization in prostate gland

A novel serine proteinase, designated as prostasin, has been purified from human seminal fluid to apparent homogeneity by DEAE-Sepharose CL-6B and aprotinin-affinity chromatography. The purified protein migrates as two close bands with an apparent molecular mass of 40 kDa on SDS-polyacrylamide gel electrophoresis under reducing conditions. It can be labeled with [14C]diisopropyl fluorophosphate and has a pI ranging from 4.5 to 4.8. Sequence analysis reveals that the two protein bands have an identical NH2-terminal amino acid sequence which is different from any known protein sequence in the SwissPro or GenBank data base. The NH2-terminal 20-amino acid sequence shares 50-55% identity with human alpha-tryptase, elastase 2A and 2B, chymotrypsin, acrosin, and the catalytic chains of hepsin, plasma kallikrein, and coagulation factor XI. Prostasin has trypsin-like activity with a pH optimum of 9.0, hydrolyzing peptidyl fluorogenic substrates: D-Pro-Phe-Arg-MCA, D-Phe-Phe-Arg-MCA, D-Val-Leu-Arg-MCA, and Z-Gly-Pro-Arg-AFC. It is inhibited by aprotinin, antipain, leupeptin, and benzamidine. The tissue distribution of prostasin was determined by a newly developed radioimmunoassay. Linear displacement curves for immunoreactive prostasin in body fluids and tissues were parallel with the standard curve of purified prostasin, indicating their immunological identity. Immunoreactive prostatin levels were 8.61 +/- 0.42 microgram/ml in the seminal fluid and 0.201 +/- 0.029 microgram/ml in urine. Prostasin is present at high levels in the prostate gland (143.7 +/- 15.9 ng/mg protein), moderate levels (2-6 ng/mg protein) in colon, lung, kidney, pancreas, salivary gland, liver, and bronchi, but it is not detected in the brain, muscle, testis, ventricle, atrium, and aorta. Immunohistochemical localization reveals that prostasin is present in epithelial cells and ducts of the prostate gland. These studies indicate that prostasin purified from seminal fluid is a novel serine proteinase and originates from the prostate gland.

Activation of serpins and their cognate proteases in muscle after crush injury

Direct muscle injury was induced in rats in order to evaluate alterations in the balance of serine proteases and inhibitors (serpins) as a response to tissue damage. It was previously found that certain proteases, specifically urokinase-like plasminogen activator (uPA) and others, required activation in order to effect regeneration. We hypothesized that the magnitude and temporal sequence of serpin activation would follow, pari passu, activation of their cognate proteases. In addition to uPA, tissue PA (tPA) and tissue kallikrein were the proteases studied. The serpins we analyzed were protease nexin I (PNI), PA inhibitor 1 (PAI-1, and the kallikrein-binding protein (KBP). uPA nearly doubled 48 h after injury, while there was no change in amidolytic activity after addition of fibrin monomer as an estimation of tPA activity. Tissue kallikrein activity, barely detectable in normal muscle, slowly increased, nearly tripling at 7 days after injury. Greater magnitude and more rapid changes in muscle serpins occurred over the same post-injury time course. By 24 h PNI increased threefold, while PAI-1 increased more slowly, reaching double the control values by 5 days after injury. Surprisingly, KBP, the serpin-class inhibitor of tissue kallikrein, had the most robust response, increasing tenfold over control 48 h after crush injury of muscle. These results further implicate the serpin:protease balance in tissue injury. Participation of complex receptors, such as the alpha 2-macroglobulin receptor/low density lipoprotein receptor-related protein (LRP), various growth factors, cytokines, and other molecules, in regulating this balance is implicated by these data.

Human tissue kallikrein induces hypotension in transgenic mice

We investigated the role of the kallikrein-kinin system in blood pressure control by developing transgenic mice overexpressing human tissue kallikrein. Two lines of transgenic mice carrying the human tissue kallikrein gene under the control of the mouse metallothionein metal-responsive promoter were established. Human tissue kallikrein was identified in pancreas, salivary gland, kidney, liver, and spleen of the transgenic mice by a specific radioimmunoassay for human tissue kallikrein. The immunoreactive human tissue kallikrein reached high levels in the circulation. The linear displacement curves for the transgenic product were parallel with the human tissue kallikrein standard curve, indicating their immunologic identity. The expression of human tissue kallikrein transcript in the transgenic mice was further confirmed by Northern blot analysis and by reverse transcription-polymerase chain reaction followed by Southern blot. Both lines of transgenic mice had significantly lowered blood pressure (86.4 +/- 13.5 mm Hg [mean +/- SD], n = 8 and 78.9 +/- 12.4 mm Hg, n = 8) compared with control mice (100.9 +/- 5.0 mm Hg, n = 8). Induction with zinc did not lower the blood pressure further despite elevated expression of the transgene. Administration of aprotinin, a potent tissue kallikrein inhibitor, restored the blood pressure of the transgenic mice but had no significant effect on control littermates. Our findings raise the possibility of tissue kallikrein being a powerful modulator of blood pressure and provide a new animal model for the study of blood pressure regulation.

Subcellular distribution of tissue kallikrein and Na,K-ATPase alpha-subunit in rat parotid striated duct cells

Intracellular protein distribution and sorting were examined in rat parotid striated duct cells, in which tissue kallikrein is apical, and Na,K-ATPase is basolateral. Electron-microscopic immunogold cytochemistry, with both polyclonal and monoclonal antibodies, demonstrated these enzymes at opposite poles of the cells and in distinct intracellular sites. Kallikrein was found within apical secretory granules, whereas Na,K-ATPase was present on basolateral cell membranes. In addition, kallikrein was localized throughout cisternae of all Golgi profiles, whereas Na,K-ATPase (alpha-subunit) was found only in small peripheral vesicles and/or lateral cisternal extensions of a basal subset of Golgi profiles. These differences in the subcellular distribution of the two marker antigens were most clearly seen with double immunogold labelling. Our results suggest that kallikrein, an apical, regulated secretory protein, and Na,K-ATPase, a basolateral, constitutively transported membrane protein, are segregated at (or prior to) the level of the Golgi apparatus rather than in the trans-Golgi network (TGN), as was expected.

Kallistatin: a novel human serine proteinase inhibitor. Molecular cloning, tissue distribution, and expression in Escherichia coli

We have recently purified a novel human serine proteinase inhibitor (serpin), designated as kallistatin, which binds to tissue kallikrein and inhibits kallikrein's kininogenase and amidolytic activities. In the present studies, we have cloned a full-length cDNA encoding kallistatin from human liver RNA by the polymerase chain reaction. The cDNA is 1284 base pairs in length and encodes 427 amino acid residues, including a 26-residue signal peptide and a 401-residue mature peptide. The translated amino acid sequence of kallistatin matches with the protein sequence and shares 44-46% sequence identity with human alpha 1-antichymotrypsin, protein C inhibitor, corticosteroid-binding globulin, alpha 1-antitrypsin, thyroxin-binding globulin, and rat kallikrein-binding protein. Kallistatin is a new member of the serpin superfamily with a unique reactive site P1-P1' of Phe-Ser. Four potential glycosylation sites are found in the translated amino acid sequence of kallistatin. In a Southern blot analysis following reverse transcription and polymerase chain reaction, kallistatin was found to be expressed in human liver, stomach, pancreas, kidney, aorta, testes, prostate, artery, atrium, ventricle, lung, renal proximal tubular cell, and a colonic carcinoma cell line T84. A genomic Southern blot using the full-length kallistatin cDNA probe revealed simple banding patterns suggesting the gene encoding kallistatin is single-copied. The kallistatin cDNA encoding the mature peptide was expressed in Escherichia coli. The recombinant kallistatin forms an SDS-stable complex with 125I-human tissue kallikrein and has a molecular mass of 40 kDa. The cloning of human kallistatin cDNA established the identity of the novel kallikrein inhibitor and its expression in a functional form in E. coli provides means for studying its structure-function relationship through protein engineering.

A prospective review system of nonurgent consultation requests in a family medicine residency practice

BACKGROUND

This study describes a system for prospectively reviewing non-urgent consultation or referral requests in a family practice residency program.

METHODS

A committee composed of four rotating family physicians met weekly during a 22-month period to review all non-urgent proposed consultations. The committee either approved consultations or made other recommendations to the primary care physician for clinical management. Data were prospectively recorded to determine what types of referrals were most commonly made and approved, and if the number of consultations changed after the system was instituted.

RESULTS

The committee reviewed 930 non-urgent consultation requests. The consultation request rate was 2.5 per 100 patients seen. The number of consultation requests declined significantly over the study period. (P = .0007) Seventy-two percent of consultation requests were approved; 28% were not and resulted in recommendations for alternate management. Non-approval was most likely for referrals to specialists in podiatry, rheumatology, endocrinology, neurology, gastroenterology, cardiology, and allergy. The approval rate for consultations was not significantly related to patient age, sex, or type of health insurance. Patients with multiple consultation requests were more likely to have a prepaid health insurance plan or governmental insurance than private insurance.

CONCLUSIONS

Prospective review of consultations and referrals can result in a decrease in the rate of consultations and referrals made by family physicians. Alternative management can frequently be recommended. Potential benefits of this system may include significant medical care cost savings and education for physicians.

Molecular cloning and sequence analysis of the monkey and human tissue kallikrein genes

Cynomolgus monkey renal kallikrein cDNA and genomic human tissue kallikrein gene were cloned. The monkey gene encodes a 257 amino acid (aa) preprokallikrein and exhibits 95% and 92% homology to the human at nucleotide (nt) and aa level, respectively. The monkey gene encodes a 233-aa mature kallikrein versus a 238-aa in human. The human kallikrein gene and urinary kallikrein both contain a Lys-162 instead of the reported Glu-162. Human, monkey and rat renal/pancreatic kallikrein genes evolve with a N-glycosylation containing domain (aa 81-87) which is absent in porcine and is non-glycosylable in mice. Only human kallikrein evolves with an additional Thr-108 and with a N-glycosylation site at aa-141.

Expression and characterization of rat kallikrein-binding protein in Escherichia coli

Rat kallikrein-binding protein is a novel serine-proteinase inhibitor that forms a covalent complex with tissue kallikrein. We have purified rat kallikrein-binding protein and cloned the cDNA and the gene encoding rat kallikrein-binding protein [Chao, Chai, Chen, Xiong, Chao, Woodley-Miller, Wang, Lu and Chao (1990) J. Biol. Chem. 265, 16394-16401; Chai, Ma, Murray, Chao and Chao (1991) J. Biol. Chem. 266, 16029-16036]. In the present study, we have expressed rat kallikrein-binding protein in Escherichia coli with a T7-polymerase/promoter expression system. A high level of expression was detected by an e.l.i.s.a. with an average of 24.2 mg of recombinant rat kallikrein-binding protein per 1 of culture. The recombinant protein appeared as a major protein in a crude extract of Escherichia coli on SDS/PAGE. It showed a molecular mass of 43 kDa and was recognized by polyclonal antibody to the native rat kallikrein-binding protein in Western-blot analysis. The recombinant rat kallikrein-binding protein has been purified to apparent homogeneity by DEAE-Sepharose CL-6B, hydroxyapatite Bio-Gel HPHT and Mono P 5/5 column chromatography. The purified recombinant rat kallikrein-binding protein showed immunological identity with the native rat kallikrein-binding protein purified from rat serum, in a specific e.l.i.s.a. To confirm the fidelity of the expression, the N-terminal ten amino acids of the recombinant rat kallikrein-binding protein were sequenced and were shown to match perfectly with those of the native rat kallikrein-binding protein. The purified recombinant rat kallikrein-binding protein formed SDS- and heat-stable complexes with rat tissue kallikrein (rK1) and T-kininogenase (rK10) in vitro, but not with other enzymes in the rat kallikrein gene family, such as tonin (rK2) and S3 protein (rK9), which indicates enzyme-specific binding. The properties of the recombinant rat kallikrein-binding protein including its size, charge, complex formation with target enzymes and immunological characteristics were compared with those of the native protein. This expression system provides a simple way to obtain a large amount of the biologically active recombinant protein, to study structure-function relationships of the rat kallikrein-binding protein and its interaction with its target enzymes.

Regulation of kininogen gene expression and localization in the lung after monocrotaline-induced pulmonary hypertension in rats

Pyrrolizidine monocrotaline (MCT) from plant seed produces pulmonary endothelial cell injury, pulmonary hypertension, and inflammation in rats, providing a useful animal model for studying progressive pulmonary vascular disease. Kininogen is the precursor of proinflammatory kinins and may also exert anti-inflammatory actions by inhibiting cysteine proteinases. Given the potential roles of kininogen in vascular injury and inflammation, we have investigated the regulation of kininogen gene expression in the MCT-induced pulmonary hypertensive rat model. Sprague-Dawley rats, in groups of six, were given a single subcutaneous injection of monocrotatine (60 mg/kg body wt) and sacrificed 10 and 20 days later. Northern blot hybridization using a kininogen cDNA probe showed kininogen gene expression in the liver, lung, and kidney. MCT treatment induced a time-dependent increase in kininogen mRNA levels, whereas it reduced rat alpha 1-antitrypsin and kallikrein-binding protein mRNA levels in the liver. Similarly, kininogen mRNA levels were low in the normal lung and were increased 7.5- and 13.7-fold, respectively, after MCT injection for 10 and 20 days. Immunoreactive kininogen levels in perfused liver and lung extracts of rats receiving MCT injection increased up to 20-fold, as measured by a T-kininogen radioimmunoassay. Western blot analyses showed that a 68-kilodalton immunoreactive kininogen increased in the serum and lung extracts of MCT-treated rats compared to those in the control rats. In control rats, immunostaining for kininogen in the lung was most marked in venous endothelial cells and alveolar macrophages. After MCT treatment, staining for kininogen increased dramatically throughout the lung tissues, often covering the epithelial surfaces of alveoli and bronchi. The present studies have shown that the toxin MCT altered the synthesis and distribution of pulmonary kininogen and suggest that the kininogen/kinin system may be associated with the pulmonary vascular injury, remodeling, and inflammation seen in this animal model.

Upregulation of renin-angiotensin system and downregulation of kallikrein in obstructive nephropathy

The purpose of this study was to delineate the effects of prolonged (1 and 5 wk) unilateral ureteral obstruction (UUO) on the intrarenal renin-angiotensin and kallikrein-kinin systems in the rat. Systolic blood pressure (SBP) and plasma angiotensin (ANG) II levels were significantly higher at 1 and 5 wk of obstruction than in sham-operated groups. Also, plasma renin activity and ANG I levels were elevated at 1 wk (P < 0.05), and plasma angiotensin-converting enzyme (ACE)-kininase II activity was elevated at 5 wk (P < 0.05). Blockade of ANG II receptors with losartan (Dup 753) prevented the rise in SBP after UUO and normalized SBP in chronically hypertensive UUO rats. Renin mRNA levels and ANG II content were elevated in the obstructed kidneys at 1 and 5 wk compared with sham-operated kidneys (P < 0.05). ACE-kininase II activity was elevated in both the obstructed and contralateral kidneys at 5 wk compared with sham-operated kidneys (P < 0.05). In marked contrast to renin, total immunoreactive kallikrein contents and tissue kallikrein mRNA levels in the obstructed kidneys were reduced to 25% of sham-operated kidneys both at 1 and 5 wk (P < 0.001). The results indicate that urinary obstruction activates renin and suppresses kallikrein gene expression. Activation of ACE-kininase II by UUO also serves to enhance intrarenal ANG II generation and kinin degradation. The results implicate ANG II overproduction and kinin deficiency in the pathogenesis of UUO-induced hypertension and intrarenal vasoconstriction.

Lead poisoning in children

In October 1991, the Centers for Disease Control issued new recommendations lowering the acceptable blood lead level. This change was based on data indicating that irreversible adverse neurodevelopmental effects occur in children with chronic low-level exposure to lead. The primary source of lead poisoning is still lead-based paint, particularly in older urban housing. Other sources of lead poisoning are also common. Almost all U.S. children are considered at risk of lead poisoning and should be screened for lead poisoning. Parents should be provided with information about potential sources of lead during routine well-child visits. Multidisciplinary efforts should be made to reduce all lead exposure. Oral chelation therapy on an outpatient basis is now available to treat less severe cases of lead poisoning.

Tissue kallikrein and tonin levels in submandibular glands of STZ-induced diabetic rats and the effects of insulin

The levels of tissue kallikrein, tonin, and other kallikrein-like proteinases were determined in extracts of rat submandibular glands 3 mo after the induction of diabetes with STZ (65 mg/kg i.v.). Total kallikrein-like proteinase activity was assayed catalytically with the fluorogenic substrate DVLR-AFC. Tissue kallikrein was assayed by using the same substrate in the presence of SBTI. Activity of other kallikrein-like proteinases was defined as the difference between the total kallikrein-like activity and that of tissue kallikrein. Tonin was assayed by using the substrate ZVKKR-AFC in the presence of aprotinin. Results were compared with age-matched controls and with diabetic rats that had received daily insulin injections for the last week of the test period. The results showed that all activities were significantly reduced in diabetic glands compared with controls. Insulin treatment restored concentrations of tissue kallikrein activity, whereas the activities of tonin and other kallikrein-like proteinases were unchanged. RIA supported these findings. The results indicate that in rat submandibular glands, insulin affects the synthesis of kallikrein-like proteinases in different ways and, allowing for the slowness of the processes involved, insulin may exert a direct influence on the regulation of tissue kallikrein synthesis but only have indirect effects on the synthesis of tonin and the closely related kallikrein-like proteinases.

Kallistatin: a novel human tissue kallikrein inhibitor. Purification, characterization, and reactive center sequence

A novel human tissue kallikrein inhibitor designated as kallistatin has been purified from plasma to apparent homogeneity by polyethylene glycol fractionation and successive chromatography on heparin-Agarose, DEAE-Sepharose, hydroxylapatite, and phenyl-Superose columns. A purification factor of 4350 was achieved with a yield of approximately 1.35 mg per liter of plasma. The purified inhibitor migrates as a single band with an apparent molecular mass of 58 kDa when analyzed on SDS-polyacrylamide gel electrophoresis under reducing conditions. It is an acidic protein with pI values ranging from 4.6 to 5.2. No immunological cross-reactivity was found by Western blot analyses between kallistatin and other serpins. Kallistatin inhibits human tissue kallikrein's activity toward kininogen and tripeptide substrates. The second-order reaction rate constant (ka) was determined to be 2.6 x 10(4) M-1 s-1 using Pro-Phe-Arg-MCA. The inhibition is accompanied by formation of an equimolar, heat- and SDS-stable complex between tissue kallikrein and kallistatin, and by generation of a small carboxyl-terminal fragment from the inhibitor due to cleavage at the reactive site by tissue kallikrein. Heparin blocks kallistatin's complex formation with tissue kallikrein and abolishes its inhibitory effect on tissue kallikrein's activity. The amino-terminal residue of kallistatin is blocked. Sequence analysis of the carboxyl-terminal fragment generated from kallistatin reveals the reactive center sequence from P1' to P15', which shares sequence similarity with, but is different from known serpins including protein C inhibitor, alpha 1-antitrypsin, and alpha 1-antichymotrypsin. The results show that kallistatin is a new member of the serpin superfamily that inhibits human tissue kallikrein.

Differential developmental expression of the rat kininogen genes

The rat liver expresses two low molecular weight kininogens (T-KG and K-KG). Although they share 90% of the nucleotide sequence in their 5' flanking regions, T- and K-KG genes are differentially regulated. The T-KG gene is inducible, and its protein is a potent thiol-protease inhibitor. In contrast, K-KG gene is expressed constitutively and encodes the precursor of the vasoactive nonapeptide bradykinin. To further elucidate the differential regulation of T- and K-KG genes, we examined their developmental expression in the Sprague-Dawley rat. Northern blots of total liver RNA were probed with oligonucleotides complementary to T and K-KG mRNA under high-stringency conditions. A single T-KG mRNA (1.8 kb) and two K-KG mRNA species (1.6 and 2.3 kb) were consistently detected at all ages studied. Steady state T-KG mRNA levels increased 3.5-fold at birth and remained high during the 1st week of postnatal life only to decline thereafter. T-KG immunoreactivity in the liver and plasma determined by Western blot analysis paralleled T-KG mRNA expression. In marked contrast, K-KG mRNA expression was not altered during the transition from fetal to neonatal life, nor was it affected by postnatal maturation. The results demonstrate that the fetal rat liver synthesizes kininogens and that T- and K-KG genes are differentially regulated during development. Up-regulation of T-KG synthesis after birth may serve a protective function in the newborn via its antiprotease activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular cloning and characterization of rKlk10, a cDNA encoding T-kininogenase from rat submandibular gland and kidney

We have cloned and determined the nucleotide sequence of a novel kallikrein-like mRNA, designated rKlk10*, from rat submandibular gland and kidney with the aid of the polymerase chain reaction (PCR). This cDNA contains 737 base pairs comprising the sequence encoding a mature protein of 235 amino acid residues, partial zymogen peptide, and 3' noncoding sequence. Sequence comparisons showed that rKlk10 mRNA shares 87 and 88% sequence identity with rat tissue kallikrein at nucleic acid and amino acid levels, respectively. It encodes a 26,428-Da acidic protein whose derived amino acid sequence matches completely with the partial amino acid sequence of a kallikrein-like enzyme designated as T-kininogenase, K10 protein, or antigen-gamma purified from rat submandibular gland [Xiong et al. (1990) J. Biol. Chem. 265, 2822-2827; Gutman et al. (1991) Eur. J. Biochem. 784, 1-5; Berg et al. (1991) Biochem. J. 280, 19-25]. The protein encoded by rKlk10 retains the key amino acid residues determining kallikrein cleavage specificity. Northern blot analysis with an rKlk10-specific oligonucleotide probe showed that its mRNA level in the submandibular gland is decreased dramatically by administration of the beta agonist isoproterenol. Tissue-specific expression of rKlk10 was analyzed by Northern blotting and Southern blotting of PCR-amplified cDNA, which showed that rKlk10 is expressed at high levels in the submandibular gland and low levels in the kidney but not in seven other tissues including prostate, liver, heart, adrenal gland, testes, pituitary, and pancreas. rKlk10 cDNAs cloned from the kidney and submandibular gland show sequence identity.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of rat tissue kallikrein gene family members by rat kallikrein-binding protein and alpha 1-proteinase inhibitor

The regulation of tissue kallikrein activity by plasma serine proteinase inhibitors (serpins) was investigated by measuring the association rate constants of six tissue-kallikrein family members isolated from the rat submandibular gland, with rat kallikrein-binding protein (rKBP) and alpha 1-proteinase inhibitor (alpha 1-PI). Both these serpins inhibited kallikreins rK2, rK7, rK8, rK9 and rK10 with association rate constants in the 10(3)-10(4) M-1.s-1 range, whereas only 'true' tissue kallikrein rK1 was not susceptible to alpha 1-PI. This results in slow inhibition of rK1 by plasma serpins, which could explain why this kallikrein is the only member of the gene family identified so far that induces a transient decrease in blood pressure when injected in minute amounts into the circulation.

Specificity determinants of rat tissue kallikrein probed by site-directed mutagenesis

Site-specific mutagenesis was employed to study structure-function relationships at the substrate binding site of rat tissue kallikrein. Four kallikrein mutants, the Pro219 deletion (P219del), the 34-38 loop Tyr-Tyr-Phe-Gly to Ile-Asn mutation [YYFG(34-38)IN], the Trp215----Gly exchange (W215G) and the double mutant with Tyr99----His and Trp215----Gly exchange (Y99H:W215G) were created by site-directed mutagenesis to probe their function in substrate binding. The mutant proteins were expressed in Escherichia coli at high levels and analyzed by Western blot. These mutant enzymes were purified to apparent homogeneity. Each migrated as a single band on SDS-PAGE, with slightly lower molecular mass (36 kDa) than that of the native enzyme, (38 kDa) because of their lack of glycosylation. The recombinant kallikreins are immunologically identical to the native enzyme, displaying parallelism with the native enzyme in a direct radioimmunoassay for rat tissue kallikrein. Kinetic analyses of Km and kcat using fluorogenic peptide substrates support the hypothesis that the Tyr99-Trp215 interaction is a major determinant for hydrophobic P2 specificity. The results suggest an important role for the 34-38 loop in hydrophobic P3 affinity and further show that Pro219 is essential to substrate binding and efficient catalysis of tissue kallikrein.

Localization, synthetic regulation, and biology of renal atriopeptin-like prohormone

We recently demonstrated the synthesis and secretion of an atriopeptin (AP)-like prohormone in rat neonatal and adult cortical kidney cell cultures. However, these cultures contained proximal as well as distal tubular epithelial cells; thus characterization of the peptide synthetic cell was not possible. Also, by immunohistochemical techniques, we localized this AP-like prohormone to the distal cortical nephron in adult rat kidney. In this study, we examined further details of the kidney cortical cell type that expresses and secretes this AP-like peptide in adult renal cortical cell cultures, its regulation by adenylate cyclase via adenosine 3',5'-cyclic monophosphate (cAMP) generation, and its ability to stimulate guanylate cyclase. Tubular fragments were derived from cortical tissue of adult Sprague-Dawley rats and separated into four fractions on Percoll density gradient. Cell cultures generated from fraction 3 secreted 5- to 10-fold the amount of this renal peptide compared with fractions 2 and 4. Further cell culture characterization was performed by agonist-stimulated cAMP formation, kallikrein localization, and prostaglandin E2 formation. From these analyses, it was determined that tissue band 3 was enriched for distal cortical connecting tubules. To further evaluate whether mammalian distal nephron synthesizes an AP-like protein, we determined that two immortalized mouse cell lines, derived from either the distal convoluted tubule or cortical collecting tubule, synthesized a radiolabeled AP after being pulsed with [35S]-methionine.(ABSTRACT TRUNCATED AT 250 WORDS)

Biochemical characterization and substrate specificity of rat prostate kallikrein (S3): comparison with tissue kallikrein, tonin and T-kininogenase

A tissue kallikrein-like enzyme encoded by S3 mRNA was purified to homogeneity from rat prostate gland. The apparent molecular mass of the prostate enzyme is 32 kDa as determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The intact 32 kDa enzyme is split into two bands of lower molecular mass, 18 and 14 kDa, under reducing conditions on SDS-PAGE. NH2-terminal amino acid sequence analyses of the intact enzyme and heavy and light chains revealed the identity to the translated sequence of a prostate kallikrein cDNA (S3). Isoelectric focusing indicated that the prostate enzyme is a basic protein with pI of 7.30-7.45. Specific activities of the prostate kallikrein toward angiotensin I, angiotensinogen and rat low M(r) kininogen as well as tripeptide chromogenic substrates were compared with those of tissue kallikrein, tonin and T-kininogenase. The kinin-releasing activity is inhibited by leupeptin, antipain, benzamidine and soybean trypsin inhibitor. A sensitive and specific radioimmunoassay for the rat prostate kallikrein shows that the immunoreactive kallikrein levels in prostate and submandibular gland were 23.78 +/- 2.62 micrograms/mg protein (n = 5) and 12.29 +/- 2.25 micrograms/mg protein (n = 5), respectively. The results indicate that the prostate kallikrein S3 is expressed at high levels in both prostate and submandibular glands.

Differential regulation of kininogen gene expression by estrogen and progesterone in vivo

Kininogens which have multifunctional domains, serve as the precursors of potent vasoactive kinin peptides and also function as cysteine proteinase inhibitors. Given its potential role in blood pressure homeostasis and inflammation, we have examined the regulation of rat kininogen gene expression by sex hormones in vivo. Our studies indicate a differential regulation of kininogen gene expression in rat liver by estrogen and progesterone. Northern and dot blot analysis using a rat low molecular weight kininogen cDNA probe show that kininogen mRNA levels in the liver of female rats are 4-fold higher than those in male rats. Ovariectomy results in a reduction of kininogen transcripts in the liver, while estradiol replacement of the ovariectomized rats increases kininogen mRNA levels. Similarly, Northern blot analysis using a kallikrein cDNA probe shows that estradiol treatment induces an increase of kallikrein gene expression in the kidney of the same animals. In contrast, progesterone treatment of the ovariectomized rats results in an increase in renal kallikrein mRNA levels while it reduces kininogen gene expression as compared to vehicle-treated ovariectomized animals. Immunoreactive kininogen levels in the serum, analyzed by a direct radioimmunoassay and Western blot, are increased by estradiol but slightly decreased by progesterone treatment. Western blot of serum proteins on a two-dimensional polyacrylamide gel reveals that in estradiol-treated ovariectomized rats, the levels of several 68,000 Da kininogens varying in charge are markedly higher than those in ovariectomized rats. The results indicate that estrogen is one of the determinants in regulating low molecular weight kininogen gene expression in vivo. The impact of estrogen-regulated kininogen expression on cardiovascular function awaits further investigation.

Substrate specificities of tissue kallikrein and T-kininogenase: their possible role in kininogen processing

The present studies demonstrate the importance of subsite interactions in determining the cleavage specificities of kallikrein gene family proteinases. The effect of substrate amino acid residues in positions P3-P'3 on the catalytic efficiency of tissue kallikreins (rat, pig, and horse) and T-kininogenase was studied using peptidyl-pNA and intramolecularly quenched fluorogenic peptides as substrates. Kinetic analyses show the different effects of D-amino acid residues at P3, Pro at P'2, and Arg at either P'1 or P'3 on the hydrolysis of substrates by tissue kallikreins from rat and from horse or pig. T-Kininogenase was shown to differ from tissue kallikrein in its interactions at subsites S2, S'1, and S'2. As a result of these differences, Abz-FRSR-EDDnp with Arg at P'2 is a good substrate for tissue kallikreins from horse, pig, and rat but not for T-kininogenase. Abz-FRRP-EDDnp and Abz-FRAPR-EDDnp with Pro at P'2 (rat high molecular weight kininogen sequence) are susceptible to rat tissue kallikrein but not to tissue kallikreins from horse and pig. Arg at P'3 increased the susceptibility of the Arg-Ala bond to rat tissue kallikrein. These data explain the release of bradykinin by rat tissue kallikrein and of kallidin by tissue kallikreins from other animal species. Abz-FRLV-EDDnp and Abz-FRLVR-EDDnp (T-kininogen sequence) are good substrates for T-kininogenase but not for tissue kallikrein. Arg at the leaving group (at either P'1, P'2, or P'3) lowers the Km values of T-kininogenase while Val at P'2 increases its kcat values.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo catabolism of human kallikrein-binding protein and its complex with tissue kallikrein

We recently identified and purified a novel human kallikrein-binding protein (HKBP) from human plasma. The HKBP forms a 92 kd sodium dodecyl sulfate-stable and heat-stable complex with tissue kallikrein. This study was undertaken to characterize the plasma clearance and tissue distribution of exogenously administered HKBP and its complex with tissue kallikrein. Human tissue kallikrein was first incubated with purified HKBP, and the high-molecular-weight complex was separated from unbound proteins on a high-pressure liquid chromatography gel filtration column. Tissue kallikrein, kallikrein-binding protein, and their complex were labeled with iodine-125 and then injected intravenously into Sprague-Dawley rats. The disappearance rates of trichloracetic acid-precipitable radioactivity from the circulation were determined. The clearance profile of HKBP shows a nonlinear pattern with an apparent half-life of 65 minutes (n = 4). The plasma clearance of HKBP complexed with kallikrein shows a similar profile but a shorter half-life of 33 minutes (n = 3). HKBP and its complex with kallikrein were mainly taken up by the liver but to a lesser degree by the kidney, lung, and other tissues. Labeled human kallikrein has an apparent half-life of 8 minutes (n = 4), and its clearance consists of a fast and a slow component. The data indicate that kallikrein-HKBP complex is cleared from the circulation two times faster than that of the binding protein alone and that it persists in the circulation four times longer than kallikrein alone. The results support the notion that more than one pathway exists for the metabolism of tissue kallikrein and that HKBP plays a role in modulating tissue kallikrein's bioavailability.

Spatial and temporal expression of kallikrein and its mRNA during nephron maturation

To determine the relationships between nephron maturation and the ontogeny of intrarenal kallikrein, the expression and distribution of kallikrein and its mRNA were examined in fetal, neonatal, and adult Sprague-Dawley rats. Kallikrein-like immunoreactivity was first expressed 1 day before birth in the upper limb of S-shaped bodies. Immediately after birth, kallikrein immunostaining was present along the apical membranes of inner cortical distal tubules, whereas subcapsular less mature comma-shaped vesicles did not express kallikrein. After completion of nephrogenesis, kallikrein was also seen in the distal and connecting tubules of the outer cortex. In situ hybridization localized the kallikrein message in the distal tubules of inner cortical nephrons in newborns and outer cortex in adults. The transition from newborn to adult life was associated with six- and fourfold increase in renal kallikrein content and mRNA accumulation, respectively. We conclude that immature distal tubules have the transcriptional and translational capacity to express the kallikrein gene and protein and that the renal kallikrein gene is developmentally regulated. The spatial and temporal changes in intrarenal kallikrein expression during ontogeny are consistent with the hypothesis that the kallikrein-kinin system plays a role in the maturation of renal functions.

Effects of diabetes and insulin on expression of kallikrein and renin genes in the kidney

We previously showed that renal prokallikrein synthesis is reduced in streptozotocin (STZ)-diabetic rats. Plasma renin activity is also reduced in diabetic rats. To investigate the molecular mechanisms underlying these changes, we examined the effects of diabetes and insulin treatment on renal kallikrein and renal renin mRNA levels and the activities of these enzymes. Rats made diabetic by STZ were either treated with 1.5 to 1.75 U PZI insulin daily to maintain moderate hyperglycemia (plasma glucose 200 to 300 mg/dl, D + I) or left untreated to produce severe hyperglycemia (plasma glucose greater than 400 mg/dl, D). Control (C) rats were also studied. After three weeks, renal kallikrein mRNA was reduced 50% in D rats. A proportional reduction in immunoreactive kallikrein was also observed (37.8 +/- 2.5 vs. 55.8 +/- 6.8 ng/mg protein, D vs. C, P less than 0.001). Kallikrein mRNA and immunoreactive kallikrein levels in D + I rats were not different from C rats. Renin mRNA level was also markedly reduced in D rats, compared to C rats. This was associated with reduced plasma renin concentration (4.5 +/- 0.2 vs. 10.5 +/- 1.6 ng Ang I/ml/hr, D vs. C, P less than 0.01). However, renal renin concentration was unchanged (0.84 +/- 0.17 vs. 0.84 +/- 1.3 micrograms Ang I/mg protein/hr, D vs. C). In D + I rats, renin mRNA level and plasma renin concentration were not different from C levels. However, renal renin concentration was increased (1.49 +/- 0.27 micrograms Ang I/mg protein/hr) compared to C rats (P less than 0.05). beta-actin mRNA levels were unchanged in either diabetic rat group.(ABSTRACT TRUNCATED AT 250 WORDS)

New specific assays for tonin and tissue kallikrein activities in rat submandibular glands. Assays reveal differences in the effects of sympathetic and parasympathetic stimulation on proteinases in saliva

At least fourteen separate bands of proteinase activity, labelled A-N, were identified by an enzyme overlay membrane technique, using oligopeptide-7-amino-4-trifluoromethylcoumarin (AFC) substrates in rat submandibular gland extracts fractionated on pH 4-6.5 isoelectric focusing gels. The proteinases were eluted into an ammonium bicarbonate buffer pH 9.8 containing 0.1% Triton X-100 and the relative contribution of each band to total activity evaluated using D-Val-Leu-Arg-AFC (DVLR-AFC) and Z-Val-Lys-Lys-Arg-AFC (ZVKKR-AFC) as substrates. Immunoblotting of band eluants run on sodium dodecyl sulphate gels with antibodies showed that band A was identical with tonin and bands K-N contained tissue kallikrein. Tonin was found to hydrolyse ZVKKR-AFC but not DVLR-AFC. Estimates of the Km values of tissue kallikrein for DVLR-AFC and tonin for ZVKKR-AFC were found to be similar (approx. 20 microM) yet the former enzyme hydrolysed its substrate five times faster. Tonin was inhibited by soybean trypsin inhibitor (SBTI) but not by aprotinin. Tissue kallikrein, on the other hand, was inhibited by aprotinin but was considerably more resistant to inhibition by SBTI. In tissue extracts 95% of the ZVKKR-AFC lytic activity in the presence of 1 microM aprotinin is due to tonin and a similar percentage of the DVLR-AFC hydrolysing activity in the presence of 10 microM SBTI is due to tissue kallikrein. These findings were used for the specific measurement of these two proteinases in submandibular gland extracts and in saliva without prior purification. Using these inhibitor based assays we revealed qualitative differences in the composition of proteinases secreted into saliva during parasympathetic versus sympathetic stimulation of the submandibular gland. The distribution of proteinases in sympathetic saliva is very similar to that found in submandibular extracts but on parasympathetic stimulation, although much less proteinase is released, the contributions of the more acidic isomers of tissue kallikrein are increased and that of tonin and other proteinases dramatically decreased. The data suggest that parasympathetic and sympathetic nerves induce proteinase secretion via different pathways.

Expression of kallikrein-binding protein and alpha 1-antitrypsin genes in response to sex hormones, growth, inflammation and hypertension

We have recently purified rat kallikrein-binding protein (RKBP) and alpha 1-antitrypsin (alpha 1-AT) to homogeneity and isolated, sequenced cDNAs encoding these potential regulators of tissue kallikreins. Characterization of the cDNA and the gene has established the identity of the kallikrein-binding protein as a new member of the serpin (serine proteinase inhibitor) superfamily. Using the cDNA probes in Northern blot hybridization, we found a differential regulation of RKBP and alpha 1-AT gene expression in the liver. Ovariectomy results in a 67% reduction of RKBP mRNA levels but a 30% increase of alpha 1-AT mRNA levels. Estradiol or progesterone treatment of the ovariectomized rats increases RKBP transcripts by 2.5- and 6.5-fold, respectively, but reduces alpha 1-AT mRNA level by 30% and 45%, respectively. In contrast to kininogen expression, both RKBP and alpha 1-AT mRNA levels in the liver are at the lowest at birth and rapidly increase during growth and development. Rats injected with endotoxin from 4 to 24 h show a time-dependent decrease of RKBP mRNA levels while the same treatment induces alpha 1-AT gene expression. RKBP mRNA levels in the normotensive Wistar Kyoto (WKY) rats are higher than those in the spontaneously hypertensive rats (SHR) while there are no differences of alpha 1-AT mRNA levels between SHR and WKY.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative studies on P2 specificity of wild-type rat tissue kallikrein, Y99H:W215G mutant and tonin

To probe residues responsible for P2 specificity, we have recently created a mutant enzyme from rat tissue kallikrein with Tyr99 to His and Trp215 to Gly exchange (Y99H:W215G) using site-specific mutagenesis. In the present study, additional characterization of substrate specificities of both wild-type tissue kallikrein, Y99H:W215G mutant and native tonin was performed using synthetic Ac-X-Arg-pNA substrates especially designed for testing P2 specificity. Kinetic analyses of Km and kcat demonstrate a clear correlation between dramatically reduced affinity for hydrophobic P2 side-chain and the loss of the Tyr99-Trp215 hydrophobic pair. Analyses of rat tonin reveal a correlation between increased reaction rate and P2 hydrophilicity although tonin displays similar pattern in P2 affinity as compared with tissue kallikrein, suggesting a less hydrophobic environment in the substrate-binding pocket of rat tonin. The results strongly support the hypothesis that Tyr99-Trp215 interaction is the major determinant for P2 specificity and that the presence of a hydrophobic side-chain in P2 position substantially facilitates substrate hydrolysis of tissue kallikrein-like enzymes.

Localization of kallikrein gene family proteases in rat tissues

Monoclonal antibodies specific for three kallikrein gene family enzymes (tissue kallikrein, esterase A and tonin) have been used to determine the tissue and cellular distributions of these proteases as well as their association with other relevant molecules (kininogen, kallikrein-binding protein, and Na,K-ATPase alpha-subunit). Secretion of these enzymes from salivary glands was also analyzed. The results of these localization studies provide important clues to the functions of different members of this closely related family of serine proteases.

Evolution of the kallikrein gene family

All kallikrein-like genes that have been studied to date are composed of 5 exons and the tertiary structures of the encoded enzymes are remarkably similar. In the mouse and rat, these genes are highly conserved, tightly linked and tandemly arranged. In other species, such as the human, the family is less well defined and seems to be much smaller than that of the mouse and rat. Although extensively studied, the exact physiologic significance is not known for many kallikrein gene family members, however, they are thought to play important roles in processing biologically important peptide precursors. Given the potential importance of these mammalian enzymes as a group of highly selective peptide processing enzymes, it would be helpful to know more about the ways in which this family varies from species to species, especially with respect to the size of the family in each species. The evolutionary mechanisms which have shaped this family of genes are largely unknown, however, enough data has been generated to begin understanding the pathway by which this gene family has evolved.

Determinants of tissue kallikrein cleavage specificity in the limited proteolysis of kininogens

Further evidence for interactions at tissue kallikrein extended binding sites, as determinants of the kininogen cleavage specificities is presented. Differences in the cleavage sites in kininogen hydrolysis by rat and other tissue kallikreins is related to subsite S1' specificity, while the low susceptibility of rat kininogen to horse tissue kallikrein is explained by the difference in their subsite S3'.

Molecular cloning and sequence analysis of the mouse kallikrein-binding protein gene

A genomic clone (MKBP-10) encoding the mouse kallikrein-binding protein (MKBP) was isolated from a mouse genomic DNA library by screening with a rat kallikrein-binding protein (RKBP) cDNA probe. The total sequenced region of the MKBP gene spans 8615 base pairs. The exon and intron locations of the RKBP gene were identified by similarity with the RKBP gene. The MKBP gene encodes a prepeptide of 417 amino acid residues which exhibits 71% homology with RKBP. A TATA box sequence was located in the 5' flanking region of the MKBP gene by similarity with the consensus sequence TATAAAA.