Testosterone effect on the synthetic rate of two esteropeptidases in the mouse submaxillary gland

Reversible Conversion among Subtypes of Salivary Gland Duct Cells as Identified by Production of a Variety of Bioactive Polypeptides

Four major kallikreins (mK1, mK22, mK9, and mK13) were identified in the mouse submandibular gland (SMG). mK1, a true tissue kallikrein, was used as a protein marker to identify different types of SMG granular convoluted tubule (GCT) cells along with epidermal growth factor (EGF), nerve growth factor (NGF), and renin. Kallikrein mK1 was localized in a very small number (~5%) of GCT cells, which were scattered throughout the GCT, indicating that the majority of GCT cells are mK1-negative. Among mK1-positive cells, particularly strong signals were observed in a small number of narrow cells, recognized as slender granular cells (SG cells, Type IV), in the GCT. After postnatal development of the SMG, GCT cells are no longer uniform based on the bioactive substances (mK1, EGF, NGF, and renin) that they produce and secrete. GCT cells were classified into four subtypes, Types I–IV, and it became clear that these subtypes are complicatedly and reversibly converted by the endocrine hormones 5α-dihydrotestosterone (DHT) and triiodothyronine (T₃). Duct segments with similar morphology or hormone dependency were recognized in the sublingual and parotid glands. The presence of duct cells with such characteristics is therefore a common feature of the three major salivary glands of rodents.

Interference of kallikrein 1b26 (klk1b26) translation by microRNA specifically expressed in female mouse submandibular glands: an additional mechanism for sexual dimorphism of klk1b26 protein in the glands

Background

Mouse kallikrein 1b26 (klk1b26) protein is more abundant in male submandibular glands (SMGs) than in female ones. This sexual dimorphism has been thought to be due to increased mRNA synthesis stimulated by androgen. However, the klk1b26 protein level in female SMG is far less than that expected from the mRNA level, suggesting an additional mechanism for down-regulation of klk1b26 expression in female SMGs.

Methods

We examined the effects of small non-coding RNAs in mouse SMGs on in vitro translation of klk1b26 using a reticulocyte lysate system and reverse transcription (RT)-PCR for klk1b26 mRNA. Statistical analyses were performed with a computer package (Microsoft Excel).

Results

The microRNA (miRNA) preparation from female SMGs, but not male SMGs, interfered with the in vitro translation of the klk1b26 protein and inhibited the RT-PCR for klk1b26 mRNA with forward primers targeting its 5'-terminal region (between the 15th and 40th nucleotide from the 5'-terminal). The miRNA preparation from castrated mouse SMGs showed the inhibitory effect on the klk1b26 translation, but that from a 5α-dihydrotestosterone-treated female mouse SMGs did not. Synthetic miRNAs (miR-325 and miR-1497a), which have partial complementarity with klk1b26 mRNA at its 5'-terminal region (15th to 40th nucleotide position from the 5'-terminal), also interfered with the in vitro klk1b26 translation. When the female miRNA preparation was incubated with a 30-nucleotide-long single-strand oligoDNA (named [15th-44th]ssDNA, whose sequence corresponded to the 15th to 44th position from the 5'-terminal of klk1b26 mRNA) prior to the addition into the in vitro translation system, the inhibitory effect of the miRNA preparation on klk1b26 translation disappeared, while [15th-44th]ssDNA itself had no effect on the translation. Preincubation of the miRNA preparation with another single-strand DNA ([169th-198th]ssDNA, whose sequence corresponded with 169th to 198th position of klk1b26 mRNA) did not show the inhibitory effect.

Conclusions

The small non-coding RNA, most probably miRNA, specifically expressed in female mouse SMGs interfered with klk1b26 protein synthesis in the in vitro translation system. Therefore sexual dimorphism observed in klk1b26 expression in mouse SMGs is due at least in part to the female-specific small non-coding RNA in SMGs.

Thyroid hormone (3,5,3'-triido-L-thyronine) masking/inversion of stimulatory effect of androgen on expression of mk1, a true tissue kallikrein, in the mouse submandibular gland

We studied hormonal regulation of the expression of mkl, a true tissue kallikrein, in the submandibular gland (SMG) of ICR, C3H/ HeN, and F1 (mice from male C3H/HeN x female ICR and in the ones from male ICR x female C3H/HeN). In these mouse strains, mk1 was low in content in males, abundant in females, and increased remarkably by castration of males. In the case of ICR and both F1 mice, injection of 5alpha-dihydrotestosterone (DHT) reduced the mkl level of castrated and female mice. However, the mkl content in female C3H/ HeN mice (or castrated C3H/HeN) was further increased by DHT. To investigate the real action of DHT on mk1 expression, we examined the effects of adrenoectomy/glucocorticoid (dexamethasone, Dex) administration; DHT administration into castrated and adrenoectomized mice; ovariectomy/female hormone (17beta-estradiol, progesterone) administration; and hypophysectomy/combinatory administration of DHT, Dex, and thyroid hormone (3,5,3'-triiodo-L-thyronine, T3) on the mk1 expression in the SMG of ICR mice. Adrenoectomy or ovariectomy did not change the characteristic pattern of mk1 expression in male and female ICR mice. In hypophysectomized (Hypox) ICR male mice, the mk1 content was increased to the same level as in normal ICR females, and DHT administration into the Hypox mice further increased the mk1 level. However, combinatory administration of DHT + T3 or of DHT + T3 + Dex into the Hypox mice lowered the mkl content to the level of normal ICR males, whereas T3 single administration had no effect. Dex single administration into the Hypox mice increased the mkl level to an even higher than that observed with DHT administration. The mk1 level in Hypox mice was not significantly changed by coadministration of Dex with T3. From these results, we conclude that 1) mk1 expression is fundamentally stimulated by androgen (DHT) as are other mk isozymes, such as mk9, mk13, mk22, and mk26 in the mouse SMG, 2) the effect (stimulatory) of DHT on mk1 expression becomes, however, inverted (inhibitory) in the presence of T3. Although the serum T3 level of C3H/HeN female (0.52 ng/ml) was not significantly different from that of C3H/HeN males or ICR mice, coadministration of T3 into C3H/HeN females with a fixed amount of DHT (20 mg/kg body weight) dose dependently repressed the DHT-induced increase in mkl expression, suggesting the lower sensitivity of C3H/HeN females to T3.

A new electrophoretic variant of alpha subunit of Na+/K(+)-ATPase from the submandibular gland of rats

The alpha catalytic subunits of Na+/K(+)-ATPase were isolated from the kidney and brain of rats (alpha 1 and alpha 2, respectively). The antisera raised against these subunits were used as probes to analyze the isoform of catalytic subunits of Na+/K(+)-ATPase in various tissues of rats. Of 27 rat tissues examined, most had a catalytic subunit identical to alpha 1 but some, such as the nervous and muscle tissues, had both alpha 1 and alpha 2 isoforms as judged by their reactivities to antisera and their electrophoretic mobility. We found that the submandibular gland contained a new electrophoretic variant of immunoreactive alpha subunit (designated alpha(S) in this report) in addition to alpha 1 identical to those found in kidney and brain. The new variant, alpha(S), strongly cross-reacted with anti-alpha 1 antiserum, but to a lesser extent with anti-alpha 2 antiserum. The alpha(S) had a molecular mass which was found to be slightly less (approx. 90 kDa) than brain and kidney alpha 1. We examined whether or not the alpha(S) is formed by proteolytic cleavage of alpha subunits during preparation and concluded that this is not the case. The alpha(S) reacted with [gamma-32P]ATP, resulting in the formation of radioactive alpha subunit which was stabilized by 2 mM ouabain but which was labile in the presence of 70 mM potassium chloride. Since N-terminal amino acid sequence of alpha(S) protein [G()DKY()PAAVS] corresponds exactly and uniquely with the sequence of the alpha 1 chain between residues 1 and 11, it is very probable that alpha(S) protein originated from alpha 1 protein following the post-translational processing.

Trypsin-like protease and glucose-6-phosphate dehydrogenase in the human submandibular salivary gland

The proteolytic activity of N-benzoyl-D,L-arginine-p-nitroanilide hydrochloride, a trypsin-like protease, was weak, whereas strong glucose-6-phosphate dehydrogenase activity was found in all subjects. The enzyme activities of males and females were similar.

Characterization of two esteroproteases from the male mouse submandibular gland

Three major esteroproteases, proteases A and D and P-esterase, obtained from the glands were studied kinetically and chemically; two (proteases A and D) were identified. Protease A is composed of a single subunit, molecular weight (27,600) similar to the native molecule (27,000); protease D consists of three subunits, approximate molecular weights of 9200, 7600 and 4600. P-esterase contains two subunits, approximate molecular weights of 7100 and 14,000. Protease A exhibits a strong kinin-releasing activity; the other two enzymes have low activity. Protease D binds to low molecular weight-epidermal growth factor, forming a complex which has an electrophoretic mobility similar to that of high molecular weight-epidermal growth factors. When beta-nerve growth factor was incubated with protease A, the amino-terminal amino acid, serine, was lost from the growth factor and a new amino-terminal amino acid, methionine, appeared. These data indicate that proteases D and A are the same proteins as epidermal growth factor-binding protein and beta-nerve growth factor endopeptidase, respectively. From a comparison of the peptide maps of trypsin-digests of the enzymes, the proteases A and D were inferred to have a similar primary structure.

Growth-promoting actions of extracts from mouse submaxillary glands on human endothelial cells in culture

Extracts of submaxillary glands from two different strains of inbred mice were mitogenic for human endothelial cells in culture. The mitogenic activity of extracts from glands of males of the SWR/J and C57BL/10J strains were equivalent, and the growth stimulating effect was unrelated to renin or esteroproteolytic activity. Mitogenic activity in extracts from SWR/J females was less than that from males, and extracts from C57BL/10J females were inactive. The polypeptide growth factors, epidermal (EGF) and fibroblast (FGF) growth factors, also stimulated replication of endothelial cells. Cells from either umbilical arteries or veins responded to submaxillary extracts, EGF, or FGF with a similar increase in cell number, increase in protein and enhanced uptake of 3H-thymidine. The proliferative response was associated with decreased activity of angiotensin I converting enzyme which is localized on the endothelial surface. Nerve growth factor (NGF) was not mitogenic for endothelial cells. Extracts of submaxillary glands from male mice of either strain contained approximately 20 times more EGF than extracts from females, as determined by immunodiffusion. Mitogenic activity of the extracts was completely inhibited by antiserum to EGF, suggesting that the active component of these preparations is EGF.

Regulation of trypsin-like esteroprotease synthesis by 5 alpha-dihydrotestosterone and triiodothyronine in mouse submandibular gland

The hormonal regulation of trypsin-like esteroprotease synthesis in mouse submandibular gland was studied at the isozyme level. Antiserum to a mixture of two purified esteroproteases precipitated all the esteroproteases in a crude extract of this gland. Measurement of incorporation of [3H]leucine showed that total esteroprotease synthesis was stimulated by both 5 alpha-dihydrotestosterone and triiodothyronine and that the two hormones had synergistic effects. The observed correlation between the increases of synthetic rate and specific activity of this enzyme suggests that the enzyme level is regulated mainly by the rate of enzyme synthesis. Newly synthesized esteroprotease-antibody complexes gave four peaks of radioactivity with esteroprotease activity and one peak without enzyme activity on isoelectric focusing in acrylamide gel containing 8 M urea. The radioactivities of these five peaks were increased similarly by the two hormones separately or in a combination. These results suggest that the actions of androgens and thyroid homrones in esteroprotease synthesis are indistinguishable at the isozyme level.

Synergistic effects of thyroxine and glucocorticoid in induction of trypsin-like esteroprotease in mouse submandibular gland

The actions of thyroxine, 5 alpha-dihydrotestosterone and hydrocortisone singly or in combination in enzyme regulation in the submandibular gland were studied in intact and adrenalectomized female mice. 1. Adrenalectomy decreased the activity of trypsin-like esteroprotease (EC 3.4.4.-), and administration of hydrocortisone to adrenalectomized mice restored the activity to normal. 2. Hydrocortisone and thyroxine had synergistic effects in induction of esteroprotease in adrenalectomized mice, but 5 alpha-dihydrotestosterone and hydrocortisone did not have synergistic effects in either intact or adrenalectomized mice. 3. The activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) was not influenced by change in the glucocorticoid level, but was increased by thyroxine and 5 alpha-dihydrotestosterone in both adrenalectomized mice and intact mice.4. Isoelectric focusing in polyacrylamide gel showed that there are three distinct activities of esteroprotease in this gland with isoelectric points of 5.6, 6.2 and 7.3. Both thyroxine and 5 alpha-dihydrotestosterone similarly induced these activities and glucocorticoids did not affected the isozyme patterns induced by the other two hormones.

Histochemical demonstration of mouse submandibular esterproteases with a new chromogenic substrate

A new method for the histochemical demonstration of mouse submandibular esterproteases has been developed. The substrate is N-acetyl-L-methionine alpha-naphthyl ester. The main enzyme reaction was found in the apical region of the secretory tubules with a marked sex difference as expected. First attempts were made to differentiate histochemically between the various esterproteolytic enzymes.

Regulation of the secretory process of granular components from the convoluted tubular cells of the mouse submandibular gland

Autonomic regulation of the secretion of granule components in the convoluted tubular cells of male mouse submandibular glands was investigated with the use of an agar gel diffusion test using an antisera for male specific components. Whereas the injection of neither a parasympathomimetic agent (pilocarpine) nor a beta-adrenergic agent (isoproterenol) decreased the amount of the components in the glands, the injection of alpha-adrenergic agents (norepinephrine or phenylephrine) significantly decreased the amount of male specific components. Phenoxybenzamine, an alpha-blocker, completely inhibited these actions of norepinephrine and phenylephrine. These facts suggest that the alpha-adrenergic receptor participates in the secretion of male specific components present in the granules in the convoluted tubular cells of mouse submandibular glands.

Genetic control of renin activity in the submaxillary gland of the mouse

Administration of androgen to female mice is known to increase the level of several proteins in the submaxillary gland, including nerve growth factor, epidermal growth factor, esteroproteolytic activity, and renin. In the present study, renin activity has been assessed in extracts of submaxillary gland of female mice from two inbred strains (SWR/J and C57BL/10J), from F1 and F2 hybrids, and from backcrosses between F1 and parental strains. In both uninduced and induced mice, renin activity of submaxillary gland was more than 100-fold greater in SWR/J than in C57BL/10J mice as measured by either an enzymatic assay or an immunodiffusion method. This difference was not due to differences in plasma testosterone levels between the strains, and the enzymes from the two strains had similar pH optima, substrate specificities, heat stabilities, and apparent Michaelis constants. In the submaxillary gland the difference was relatively specific for renin because increases in esteroproteolytic activity, nerve growth factor, and epidermal growth factor after androgen treatment appeared to be similar in both strains. Studies with the various hybrids indicate that the difference in renin activity between the two strains is apparently due to a single regulatory gene.

Biochemical and morphological studies of rat submandibular gland: II. Partial purification of proteins from granule-rich fraction

Soluble proteins derived from a centrifuged and filtered granule-rich fraction of homogenized rat submandibular gland were analyzed by gel filtration, ion-exchange chromatography, and polyacrylamide gel electrophoresis. Both the granule-rich fraction and final supernatant fraction contained alkaline esterase activity. The major protein component, derived from granules of the convoluted tubules, was further resolved into a series of peptides ranging in molecular weight from 9,000 to 55,000 daltons.

[Esterase XX. Disc-electrophoretic investigations on the polymorphism of the esterases of the house mouse (author's transl)]

For the further clarification of the polymorphism of mouse-esterase and its hormonal control, which in part have not yet been fully comprehended, disc-electrophoretic analyses of eight organs were made, using a strain with the Tfm-mutation. In addition, quantitative assays of esterase activity as well as histochemical studies were performed. The individual organs are characterized by a specific banding pattern of esterase, which is essentially conditioned by the diverse activity of a limited number of bands. Partly these may be regarded as primary gene products, partly they seem to be secondary modifications. The few incidences of band-linkage justify the expectations, that further gene loci will be discovered. In four organs of Tfm-mutants a lower esterase activity was found than in the controls, which was especially distinct in the kidney. The behaviour of the testosterone-dependent bands in the kidneys of Tfm-mutants seems to indicate two different mechanisms of the effect of testosterone on these bands.