Matriptase Activation, an Early Cellular Response to Acidosis

Abstract

Extracellular acidosis often rapidly causes intracellular acidification, alters ion channel activities, and activates G proteincoupled receptors. In this report, we demonstrated a novel cellular response to acidosis: induction of the zymogen activation of matriptase. Acid-induced matriptase activation is ubiquitous among epithelial and carcinoma cells and is characterized by rapid onset, fast kinetics, and the magnitude of activation seen. Trace amounts of activated matriptase can be detected 1 min after cells are exposed to pH 6.0 buffer, and the vast majority of latent matriptase within the cells is converted to activated matriptase within 20 min. Matriptase activation may be a direct response to proton exposure because acid-induced matriptase activation also occurs in an in vitro, cell-free setting in which intracellular signaling molecules and ion channel activities are largely absent. Acid-induced matriptase activation takes place both on the cell surface and inside the cells, likely due to the parallel intracellular acidification that activates intracellular matriptase. Following matriptase activation, the active enzyme is immediately inhibited by binding to hepatocyte growth factor activator inhibitor 1, resulting in stable matriptase-hepatocyte growth factor activator inhibitor 1 complexes that are rapidly secreted. As an early response to acidosis, matriptase activation can also be induced by perturbation of intracellular pH homeostasis by 5-(N-methyl-N-isobutyl)-amiloride and 5-(N-ethyl-Nisopropyl)-amiloride, both of which inhibit Na ؉ /H ؉ exchangers, and diisothiocyanostilbene-2,2-disulfonic acid, which can inhibit other acid-base ion channels. This study uncovers a novel mechanism regulating proteolysis in epithelial and carcinoma cells, and also demonstrates that a likely function of matriptase is as an early response to acidosis.Matriptase, a type 2 transmembrane serine protease, is broadly expressed by epithelial and carcinoma cells (1-3), and plays essential roles in the maintenance of epithelial integrity, particularly for epidermal terminal differentiation and barrier function (4 -6). A rare human inherited genetic disorder, autosomal recessive ichthyosis, is associated with two missense mutations of the human ST14 gene, which encodes matriptase (7,8). In addition, the protease can exhibit potent oncogenic activity via ras-dependent and ras-independent pathways when it is even slightly overexpressed in the skin of transgenic mice (9). Several tumor xenograft models also provide further evidence that matriptase is strongly associated with cancer cell proliferation, invasion, and metastasis (10, 11). As is typical for classical serine proteases, matriptase is synthesized as a zymogen and must undergo activation by cleavage at Arg 614 (R2VVGG) to gain full proteolytic activity. It is the activity of the mature enzyme that is believed to be responsible for both the physiological and pathological functions of the enzyme identified by studies of animal models and human genetics (12)(13)(14).In contr...

Matriptase Expression and Zymogen Activation in Human Pilosebaceous Unit

“…The skin tissue sections were obtained with written informed consent from Tri-Service General Hospital, National Defense Medical Center under the IRB 099-05-019, approved by TSGHIRB. The specificity of these mAbs and their applications in immunohistochemical staining can be found in our previous studies (Benaud et al, 2001;Chen et al, 2011;Lin et al, 1999;Tseng et al, 2010;Wang et al, 2009). Mouse IgG was used as a negative control and the well-characterized staining at intercellular junctions and the distribution profiles in the epidermal layers (Chen et al, 2013a) were used as criteria for the quality of the immunohistochemical staining of the hair follicles.…”

“…The total matriptase mAbs M24 and M32 recognize both latent and activated forms of human matriptase. M69 mAb is specific for activated matriptase and does not recognize latent matriptase, and M19 mAb specifically recognizes human HAI-1 (Chen et al, 2010b;Lin et al, 1997;Lin et al, 1999;Tseng et al, 2010). HGF protein was detected using a goat polyclonal antibody (Santa Cruz Biotechnology Inc., Santa Cruz, CA) that recognizes the beta subunit of HGF.…”

Mechanisms for the control of matriptase activity in the absence of sufficient HAI-1

“…Matriptase activation can be induced by several nonprotease factors, including sphingosine 1-phosphate in mammary epithelial cells (2), androgens in LNCaP prostate cancer cells (10), and suramin in several matriptase-expressing epithelial and carcinoma cells (12). Aspects of the extracellular environment, such as acidity or the presence of reactive oxygen species, can also stimulate cells to activate matriptase (11,36). Once activated, matriptase must apparently immediately act on its substrates, since free-active matriptase has a very short half-life.…”

Epidermal Serine Proteases and Their Inhibitors in Atopic Dermatitis

“…Matriptase gene mutations lead to ichthyosis as recently reported (Alef et al 2008). Matriptase is immediately activated by exposure to an acidic pH, as it occurs in skin, suggesting that matriptase activation may be a direct response to proton exposure (Tseng et al 2010). Recent evidence showed that during epidermal differentiation, the matriptase-prostasin proteolytic cascade is tightly regulated by two mechanisms, either by prostasin activation temporally coupled to matriptase autoactivation or by the hepatocyte growth factor activator-inhibitor-1(HAI-1), which is rapidly inhibiting not only active matriptase but also active prostasin, resulting in an extremely brief window of opportunity for both active matriptase and active prostasin to act on their substrates (Chen et al 2010).…”