title: Effects of lysophosphatidic acid on calpain-mediated proteolysis of focal adhesion kinase in human prostate cancer cells.
abstract: BACKGROUND
  Calcium-mediated proteolysis plays an important role in cell migration. Lysophosphatidic acid (LPA), a lipid mediator present in serum, enhances migration of carcinoma cells. The effects of LPA on calpain-mediated proteolysis were, therefore, examined in PC-3, a human prostate cancer cell line.
  
  
  METHODS
  Cultured PC-3 cells were used in studies utilizing pharmacologic interventions, immunoblotting, and confocal immunolocalization.
  
  
  RESULTS
  Focal adhesion kinase (FAK), a tyrosine kinase involved in cell adhesion, is rapidly proteolyzed in serum-starved PC-3 cells exposed to the calcium ionophore, ionomycin; Nck, p130CAS, PKCα, and Ras-GAP are also degraded. Thapsigargin, which causes more moderate increases in intracellular calcium, induces partial proteolysis of these proteins. Calpain inhibitors block the proteolytic responses to ionomycin and thapsigargin. Ionomycin does not induce proteolysis in cells maintained in serum, suggesting a protective role for growth factors contained in serum. LPA causes minor FAK proteolysis when added alone, but protects against ionomycin-induced proteolysis in a time-dependent manner. LPA also protects against the cell detachment that eventually follows ionomycin treatment. The response to LPA is blocked by an LPA receptor antagonist. A similar effect of LPA is observed in ionomycin-treated Rat-1 fibroblasts. In PC-3 cells, the protective effects of LPA and serum are correlated with phosphorylation and redistribution of paxillin, suggesting roles for phosphorylation-mediated protein-protein interactions.
  
  
  CONCLUSIONS
  The complex effects of LPA on calpain-mediated proteolysis of FAK and other adhesion proteins are likely to play a role in the ability of LPA to promote attachment, migration, and survival of prostate cancer cells.
authors.affiliation: Department of Pharmacology, Medical University of South Carolina, Charleston, South Carolina, USA.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Park
authors.forename: Maria V
authors.initials: MV
authors.lastname: Rubio
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Zhang
authors.forename: Tae
authors.initials: T
authors.lastname: Um
authors.forename: Yuhuan
authors.initials: Y
authors.lastname: Xie
authors.forename: Stewart M
authors.initials: SM
authors.lastname: Knoepp
authors.forename: Ashley J
authors.initials: AJ
authors.lastname: Snider
authors.forename: Terra C
authors.initials: TC
authors.lastname: Gibbs
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Meier
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D007555:Isoxazoles / Q000494:pharmacology; D008246:Lysophospholipids / Q000494:pharmacology*; D008297:Male; D051419:Paxillin / Q000378:metabolism; D010766:Phosphorylation; D011422:Propionates / Q000494:pharmacology; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D059748:Proteolysis; D051381:Rats; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: C477898:3-(4-(4-((1-(2-chlorophenyl)ethoxy)carbonyl amino)-3-methyl-5-isoxazolyl) benzylsulfanyl) propanoic acid; D007555:Isoxazoles; D008246:Lysophospholipids; D051419:Paxillin; D011422:Propionates; D015759:Ionomycin; D019284:Thapsigargin; D051416:Focal Adhesion Protein-Tyrosine Kinases; D002154:Calpain; C032881:lysophosphatidic acid