title: Kallikrein-related peptidase 4 (KLK4) initiates intracellular signaling via protease-activated receptors (PARs). KLK4 and PAR-2 are co-expressed during prostate cancer progression.
abstract: Kallikrein-related peptidase 4 (KLK4) is one of the 15 members of the human KLK family and a trypsin-like, prostate cancer-associated serine protease. Signaling initiated by trypsin-like serine proteases are transduced across the plasma membrane primarily by members of the protease-activated receptor (PAR) family of G protein-coupled receptors. Here we show, using Ca(2+) flux assays, that KLK4 signals via both PAR-1 and PAR-2 but not via PAR-4. Dose-response analysis over the enzyme concentration range 0.1-1000 nM indicated that KLK4-induced Ca(2+) mobilization via PAR-1 is more potent than via PAR-2, whereas KLK4 displayed greater efficacy via the latter PAR. We confirmed the specificity of KLK4 signaling via PAR-2 using in vitro protease cleavage assays and anti-phospho-ERK1/2/total ERK1/2 Western blot analysis of PAR-2-overexpressing and small interfering RNA-mediated receptor knockdown cell lines. Consistently, confocal microscopy analyses indicated that KLK4 initiates loss of PAR-2 from the cell surface and receptor internalization. Immunohistochemical analysis indicated the co-expression of agonist and PAR-2 in primary prostate cancer and bone metastases, suggesting that KLK4 signaling via this receptor will have pathological relevance. These data provide insight into KLK4-mediated cell signaling and suggest that signals induced by this enzyme via PARs may be important in prostate cancer.
authors.affiliation: Institute of Health and Biomedical Innovation and School of Life Sciences, Queensland University of Technology, Corner Musk Ave. and Blamey St., Kelvin Grove, Queensland 4059, Australia.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Ramsay
authors.forename: Ying
authors.initials: Y
authors.lastname: Dong
authors.forename: Melanie L
authors.initials: ML
authors.lastname: Hunt
authors.forename: MayLa
authors.initials: M
authors.lastname: Linn
authors.forename: Hemamali
authors.initials: H
authors.lastname: Samaratunga
authors.forename: Judith A
authors.initials: JA
authors.lastname: Clements
authors.forename: John D
authors.initials: JD
authors.lastname: Hooper
mesh_terms: D000818:Animals; D001665:Binding Sites; D001859:Bone Neoplasms / Q000473:pathology / Q000556:secondary; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D018450:Disease Progression; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005453:Fluorescence; D006801:Humans; D007150:Immunohistochemistry; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism*; D007610:Kallikreins / Q000378:metabolism* / Q000494:pharmacology; D008297:Male; D051379:Mice; D010455:Peptides / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000473:pathology*; D044463:Receptor, PAR-1 / Q000378:metabolism*; D044464:Receptor, PAR-2 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D010455:Peptides; D010750:Phosphoproteins; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D048049:Extracellular Signal-Regulated MAP Kinases; D007610:Kallikreins; C120801:kallikrein 4; D002118:Calcium