Purification, characterization, and localization of follipsin, a novel serine proteinase from the fluid of porcine ovarian follicles

Localization of bradykinin B(2) receptor in the follicles of porcine ovary and increased expression of matrix metalloproteinase-3 and -20 in cultured granulosa cells by bradykinin treatment

We have recently shown that not only bradykinin, but also all components for the production of bradykinin, can be detected within the follicle of porcine ovaries. To elucidate the relevance of the intrafollicular bradykinin-producing system to its physiological role, we investigated the distribution of bradykinin receptor (B(2)R) mRNA and the protein in porcine ovaries. A cDNA encoding porcine B(2)R was first cloned from a porcine uterus cDNA library. The receptor mRNA was scarcely detected in the ovary by Northern blot analysis. Polymerase chain reaction analysis with total RNAs isolated from the ovary and from granulosa cells of small and large follicles demonstrated the ovarian expression of B(2)R mRNA. The B(2)R protein was detected by Western blot analysis in extracts of isolated granulosa cells. In situ hybridization of B(2)R mRNA and immunohistochemical analysis of the protein revealed that the receptor is expressed in the theca and granulosa cells of all growing follicles. The effect of bradykinin on the expression of some matrix metalloproteinase (MMP) genes was examined using isolated granulosa cells. Bradykinin treatment induced MMP-3 and MMP-20 gene expression to an extreme degree. The expression of MT1-MMP was also affected by bradykinin treatment. These results suggest that MMPs play a role in follicle rupture during ovulation. The present study provides new information regarding the mechanisms of bradykinin-induced ovulation in porcine ovaries.

Identification of components of the intrafollicular bradykinin-producing system in the porcine ovary

As a step in elucidating the biological role of plasma kallikrein (PK) present in the follicular fluid of mammalian ovaries, we examined pig ovary fluid to determine its constituent activators and substrates. Using the inactive precursor form of plasma kallikrein (prePK) as a substrate, we purified an enzyme capable of activating this protein. The prePK-activating enzyme was shown to be the active enzyme blood coagulation factor XIIa. We also isolated high molecular weight kininogen (HMW-K) from the same fluid. Incubation of HMW-K with the ovarian follicular fluid PK resulted in the production of the nanopeptide bradykinin (BK). Expression of prePK, blood coagulation factor XII, and HMW-K was examined by Northern blot analysis using ovary and liver poly(A)(+) RNA. All these transcripts were found in the liver, but none were found in the ovary. In addition, it was found that BK levels in the fluid derived from the small follicles were approximately 6 times higher than those from medium and large follicles. These results demonstrate the presence of a BK-producing system in the ovarian follicles and suggest the physiological importance of this peptide hormone in the early stages of follicular development and at ovulation.

Identification and partial characterization of a metallopeptidase from porcine ovaries

The follicular fluid of porcine ovaries contains an EDTA-sensitive enzyme activity for the synthetic substrate benzyloxycarbonyl-Val-Lys-Met-4-methylcoumaryl-7-amide. To investigate its characteristics and its identification, the enzyme was partially purified by ammonium sulfate fractionation followed by column chromatographies on DEAE-Cellulose and chelating Cellulofine columns. The enzyme activity was strongly inhibited by typical chelators, such as EDTA and o-phenanthroline, but after inhibition by EDTA the activity was completely restored with an appropriate amount of Zn2+ and Co2+ ions. It showed enzyme activity solely for benzyloxycarbonyl-Val-Lys-Met-4-methylcoumaryl-7-amide among the substrates tested. The molecular weight of the enzyme was estimated to be 400,000 by gel filtration. The enzyme activity in the fluid obtained from large follicles of porcine ovaries was significantly higher than that from smaller follicles. It appeared that the granulosa cell extract did not contain the metalloenzyme activity. Similar enzyme activities were detected in follicular fluids from bovine and human ovaries. These results suggest that the present enzyme is distinct from any other metalloendopeptidases thus far reported.

Identification and activation of profollipsin, a latent precursor form of porcine follipsin

A latent protease has been identified in column fractions obtained during the purification of the porcine ovarian serine protease follipsin. The latent enzyme was readily activated by trypsin treatment. The trypsin-activated enzyme was purified using a benzamidine-Sepharose 6B column and was shown to be composed of two distinct, covalently associated polypeptides with Mr of 45000 and 32000. This polypeptide chain composition, together with its substrate specificity, inhibition profile using various protease inhibitors, cross-reactivity with anti-follipsin antibody, and ability to activate single-chain precursor tissue plasminogen activator, indicated its identity as porcine follipsin. The activation of the enzyme with trypsin was found to occur by the hydrolysis of an internal peptide bond resulting in a two-chain structure. Thus, we conclude that the latent enzyme is the inactive precursor form (profollipsin) of follipsin. The present study also shows that the follicular fluid of porcine ovary contains a profollipsin-activating enzyme activity.

Purification and molecular cloning of carp ovarian cystatin

The ovarian fluid of carp consists of many components. Using the antiserum against carp serum, Western blot analysis of ovarian fluid was done in order to distinguish substances synthesized by the ovary from those derived from the serum. Several ovary-specific substances were detected including a protein of 12 kDa (p12), which was purified to homogeneity. Purified p12 displays a single band in SDS-PAGE under nonreducing condition and it can inhibit the enzymatic activity of papain with an apparent inhibition constant of 0.01 nM. The primary structure of p12 was partially determined by Edman degradation and fully elucidated by molecular cloning. A cDNA of 531 bp encoding p12 was obtained. The precursor of p12 has 129 residues, including a signal peptide of 18 residues and a mature protein of 111 residues. The N- and C-terminus of p12 are threonine and methionine, respectively. The p12 shares many common features of the family 2 cystatins of other species, including the similarity of the protein size (in the range of 110 to 120 residues), the presence of 4 cysteine residues and the occurrence of invariant residues throughout the molecule.

The N-terminal peptide of the inhibin alpha subunit What are its endocrine and paracrine roles?

alphaN inhibin (molecular mass 23 24 kD) is present in the pro-alphaN-alphaC subunit of inhibin and can be released by cleavage at the flanking arginine residues during posttranslational processing. Although the alphaN protein isolated from bovine follicular fluid has no inhibinlike (FSH suppressing) activity, alphaN is present in high molecular weight forms of biologically active inhibin found in follicular fluid and plasma. alphaN may modify the biological activity of inhibin by influencing its half-life or access to its receptor. alphaN may also play a role in regulating fertility through a local action on ovulation by the ovary that is independent of the actions of inhibin. The evidence suggests a unique physiological significance for the precursor peptides of the inhibin-alpha subunit in both the endocrine and paracrine control of fertility.

Cleavage specificity of porcine follipsin

Follipsin purified from the follicular fluid of porcine ovaries was studied for its specificity against various synthetic and peptide substrates. The enzyme cleaved only by an endopeptidase activity at the amide and peptide bonds of Arg-X, indicating strict specificity of the S1 pocket for arginine. The specificity for pocket S2 appears to favor either hydrophobic or basic side chains. A 10-residue peptide containing a portion of the activation site of human tissue plasminogen activator was synthesized and tested with the enzyme. The peptide was cleaved by follipsin at the Arg-Ile bond, as expected from the specificity deduced above. Furthermore, the enzyme successfully converted single-chain precursor tissue plasminogen activator (sctPA) to its active, two-chain form by cleaving the corresponding peptide bond. Comparison of the rates of single-chain precursor tissue plasminogen activator activation and tissue plasminogen activator peptide hydrolysis revealed that the former is a more efficient substrate than the latter.