title: Kallikrein-related peptidase 4: a new activator of the aberrantly expressed protease-activated receptor 1 in colon cancer cells.
abstract: 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.
authors.affiliation: INSERM U773, Faculté de Médecine Xavier Bichat 75018 Paris, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Gratio
authors.forename: Nathalie
authors.initials: N
authors.lastname: Beaufort
authors.forename: Lina
authors.initials: L
authors.lastname: Seiz
authors.forename: Josefine
authors.initials: J
authors.lastname: Maier
authors.forename: G Duke
authors.initials: GD
authors.lastname: Virca
authors.forename: Mekdes
authors.initials: M
authors.lastname: Debela
authors.forename: Nicolai
authors.initials: N
authors.lastname: Grebenchtchikov
authors.forename: Viktor
authors.initials: V
authors.lastname: Magdolen
authors.forename: Dalila
authors.initials: D
authors.lastname: Darmoul
mesh_terms: D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism; D003110:Colonic Neoplasms / Q000201:enzymology* / Q000473:pathology*; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D019073:HT29 Cells; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D007610:Kallikreins / Q000378:metabolism*; D044463:Receptor, PAR-1 / Q000378:metabolism*; D044464:Receptor, PAR-2 / Q000378:metabolism
chemical_list: D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D048049:Extracellular Signal-Regulated MAP Kinases; D007610:Kallikreins; C120801:kallikrein 4