Matrix metalloproteinases (MMPs) are Zn(2+)-binding endopeptidases that degrade various components of the extracellular matrix (ECM). The MMPs are enzymes implicated in normal and pathologic tissue remodeling processes, wound healing, angiogenesis, and tumor invasion. MMPs have different substrate specificities and are encoded by different genes. Sato et al. (1994) cloned a cDNA for the human gene from a placenta cDNA library (they called the gene MMP-X1 and the gene product membrane-type metalloproteinase).
Proteins of the matrix metalloproteinase (MMP) family are involved in the breakdown of extracellular matrix in normal physiological processes, such as embryonic development, reproduction, and tissue remodeling, as well as in disease processes, such as arthritis and metastasis. Most MMP's are secreted as inactive proproteins which are activated when cleaved by extracellular proteinases. However, the protein encoded by this gene is a member of the membrane-type MMP (MT-MMP) subfamily; each member of this subfamily contains a potential transmembrane domain suggesting that these proteins are expressed at the cell surface rather than secreted. This protein activates MMP2 protein, and this activity may be involved in tumor invasion.
Enzyme, Hydrolase, Peptidase/Protease
In the ovary, extensive tissue remodeling is required during both follicular development and the break down of the follicular
wall at the time of ovulation. Extracellular proteases such as serine proteases and matrix metalloproteinases (MMPs) are
thought to play pivotal roles in these processes.
Extracellular Matrix, Plasma membrane
Liu et al used in situ hybridization to study the regulation and distribution of mRNA coding for MMP-2 (gelatinase A) and its cell surface activator membrane-type MMP1 (MT1-MMP)
during gonadotropin induced ovulation in the rat. In ovaries of untreated immature rats, the levels of MT1-MMP
and MMP-2 mRNA were low. MMP-2 mRNA was found in theca-interstitial cells while MT1-MMP mRNA was found in
both granulosa and theca-interstitial cells and both messages were induced after stimulation with PMSG. After an ovulatory
dose of hCG, the expression of MT1-MMP was dramatically down regulated in the granulosa cell layers of large
preovulatory follicles but the expression remained and appeared to be up regulated together with MMP-2 in the
theca-interstitial cells surrounding the large preovulatory follicles. The expression kinetics and tissue distribution supports
the notion that MT1-MMP may have dual functions in the ovary. Initially MT1-MMP may act as a matrix degrading protease
inside the follicle during follicular development and later, just prior to ovulation, as an activator of proMMP-2 in
theca-interstitial cells surrounding preovulatory follicles.
Expression regulated by
Membrane Type 1-Matrix Metalloproteinase (MMP)-Associated MMP-2 Activation Increases in the Rat Ovary in Response to an Ovulatory Dose of Human Chorionic Gonadotropin.
Jo M, et al .
Gonadotropins stimulate ovarian proteolytic enzyme activity that is believed to be important for the remodeling of the follicular extracellular matrix. Membrane type 1-matrix metalloproteinase (MT1-MMP) has been identified in vitro as an activator of pro-MMP-2 by forming a complex with tissue inhibitors of metalloproteinase-2 (TIMP-2). In the present study, the expression pattern of MT1-MMP mRNA and the role of MT1-MMP were examined in the ovary using the gonadotropin-treated immature rat model. Ovaries were collected at selected times after eCG or hCG. RNase protection assays revealed a transient increase in MT1-MMP mRNA beginning 4 h after hCG. High expression of MT1-MMP mRNA was localized to the theca-interstitial layer of developing and preovulatory follicles, while low expression was observed in the granulosa cell layer of developing follicles by in situ hybridization. The localization pattern of MT1-MMP mRNA was compared with TIMP-2 mRNA. Both MMP-2 and TIMP-2 mRNA were expressed in the theca layer of preovulatory follicles, showing a similarity to MT1-MMP mRNA expression. To further determine whether MT1-MMP activates pro-MMP-2 in the ovary, crude plasma membrane fractions from preovulatory ovaries were analyzed by gelatin zymography. In plasma membrane fractions, pro-MMP-2 increased around the time of ovulation. Upon incubation, pro-MMP-2 was activated with the highest levels of activation at 12 h post-hCG. The addition of MT1-MMP antibody or excess TIMP-2 to membrane fractions inhibited pro-MMP-2 activation. The increase in MT1-MMP mRNA may be an important part of the mechanism necessary for the efficient generation of active MMP-2 during the ovulatory process.
Granulosa, Theca, Luteal cells
Liu et al examined the physiological regulation pattern and cellular distribution of messenger RNAs coding for membrane type MMP 1 (MT1-MMP, MMP-14) in the CL of adult pseudopregnant (psp) rat. MT1-MMP, known to activate progelatinase A and procollagenase-3 in vitro, was constitutively expressed during the formation, function, and regression of the CL and may therefore be involved in the activation of these MMPs.
Preovulatory, Corpus luteum
Species: mouse -
type: null mutation fertility: unknown Comment:Holmbeck et al. (1999) generated mice deficient in the Mmp14 gene, which they called MT1-MMP.
MMP14 deficiency caused craniofacial dysmorphism, arthritis, osteopenia, dwarfism, and fibrosis of soft tissues due to
ablation of a collagenolytic activity that is essential for modeling of skeletal and extraskeletal connective tissues.