Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.5 (thrombin)
 33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hepatocyte growth factor activator (HGFA) is a serine protease and a potent activator of prohepatocyte growth factor/scatter factor (pro-HGF/SF), a multifunctional growth factor that is critically involved in tissue morphogenesis, regeneration, and tumor progression. HGFA circulates as a zymogen (pro-HGFA) and is activated in response to tissue injury. Although thrombin is considered to be an activator of pro-HGFA, alternative pro-HGFA activation pathways in tumor microenvironments remain to be identified. In this study, we examined the effects of kallikrein 1-related peptidases (KLKs), a family of extracellular serine proteases, on the activation of pro-HGFA. Among the KLKs examined (KLK2, KLK3, KLK4 and KLK5), we identified KLK4 and KLK5 as novel activators of pro-HGFA. Using N-terminal sequencing, the cleavage site was identified as the normal processing site, Arg407-Ile408. The activation of pro-HGFA by KLK5 required a negatively charged substance such as dextran sulfate, whereas KLK4 could process pro-HGFA without dextran sulfate. KLK5 showed more efficient pro-HGFA processing than KLK4, and was expressed in 50% (13/25) of the tumor cell lines examined. HGFA processed by these KLKs efficiently activated pro-HGF/SF, and led to cellular scattering and invasion in vitro. The activities of both KLK4 and KLK5 were strongly inhibited by HGFA inhibitor type 1, an integral membrane Kunitz-type serine protease inhibitor that inhibits HGFA and other pro-HGF/SF-activating proteases. These data suggest that KLK4 and KLK5 mediate HGFA-induced activation of pro-HGF/SF within tumor tissue, which may thereafter trigger a series of events leading to tumor progression via the MET receptor.
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PMID:Activation of hepatocyte growth factor activator zymogen (pro-HGFA) by human kallikrein 1-related peptidases. 1822 92

In prostate cancer, the mechanism by which the stromal cells surrounding the cancer epithelium become reactive and overproduce growth factors is unclear. Furthermore, the precise process of how these stromal cells stimulate the cancer epithelium is not fully understood. We recently found that protease-activated receptor-1 (PAR-1) in these reactive stromal cells is upregulated. To investigate the role of PAR-1 in the stromal-epithelial interaction, WPMY-1 stromal myofibroblasts were stimulated with PAR-1 agonists including thrombin and PAR-1 activating peptide. We show that WPMY-1 cells have functional PAR-1 by signaling through ERK1/2. Conditioned media (CM) from PAR-1 agonists-treated WPMY-1 cells stimulate the epithelial LNCaP cells leading to ERK1/2 activation and cell proliferation. Cytokine array analysis of the CM demonstrates that PAR-1 induces stromal cells to release numerous cytokines, of which interleukin 6 (IL-6) is the major factor responsible for mitogenic signaling in LNCaP cells. CM further induces expression of prostate-specific kallikrein-related peptidase-3 (KLK3/PSA) and KLK4 in LNCaP cells via the IL-6 pathway. Moreover, KLK4 functions as a potent agonist of PAR-1 by cleaving the receptor at the proper site on cell surface. KLK4 triggers transmembrane signaling and upregulates IL-6 in WPMY-1 cells through PAR-1. Immunohistochemical analysis indicates that PAR-1 is predominantly expressed in peritumoral stroma while KLK4 is produced exclusively by the epithelial cancer cells. These data provide evidence for a novel double-paracrine mechanism whereby cancer epithelium produces KLK4 to activate PAR-1 in the surrounding stroma, which in-turn releases cytokines (IL-6) that stimulate cancer cells to proliferate and increase production of KLKs.
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PMID:Kallikrein-related peptidase-4 initiates tumor-stroma interactions in prostate cancer through protease-activated receptor-1. 1979 18

Certain serine proteases are considered to be signaling molecules that act through protease-activated receptors (PARs). Our recent studies have implicated PAR1 and PAR4 (thrombin receptors) and PAR2 (trypsin receptor) in human colon cancer growth. Here we analyzed the expression of KLK4, a member of the kallikrein-related peptidase (KLK) family of serine proteases and explored whether this member can activate PAR1 and PAR2 in human colon cancer cells. Immunohistochemistry showed KLK4 expression in human colon adenocarcinomas and its absence in normal epithelia. KLK4 (1 micromol/L) initiated loss of PAR1 and PAR2 from the HT29 cell surface as well as increased intracellular calcium transients in HT29 cells. This KLK4-induced Ca2+ flux was abrogated after an initial challenge of the cells with TRAP (SFLLR-NH2; 100 micromol/L), which is known to desensitize PAR1 and PAR2. Interestingly, PAR1 blocking antibody, which inhibits cleavage and activation by thrombin, dramatically reduced KLK4-induced Ca2+ influx, but blocking cleavage of PAR2 failed to attenuate the KLK4-induced Ca2+ flux. Consistently, desensitization with AP1 (TFFLR-NH2), targeting PAR1, attenuated most of the Ca2+ flux induced by KLK4. KLK4 also induced a rapid and significant ERK1/2 phosphorylation in HT29 cells. Our results demonstrate, for the first time, that KLK4 is aberrantly expressed in colon cancer and capable of inducing PAR1 signaling in cancer cells. These data suggest that KLK4 signaling via PAR1 may represent a novel pathway in colon tumorigenesis.
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PMID:Kallikrein-related peptidase 4: a new activator of the aberrantly expressed protease-activated receptor 1 in colon cancer cells. 2005 42