title: Differential regulation of stress proteins by high hydrostatic pressure, heat shock, and unbalanced calcium homeostasis in chondrocytic cells.
abstract: High hydrostatic pressure (HP) has recently been shown to increase cellular heat shock protein 70 (Hsp70) level in a specific way that does not involve transcriptional activation of the gene, but rather the stabilisation of the mRNA for Hsp70. In this study, we investigated whether there are other observable changes caused by HP stress, and compared them with those induced by certain other forms of stressors. A chondrocytic cell line T/C28a4 was exposed to 30 MPa continuous HP, heat shock at 43 degrees C, and increased cytosolic calcium concentration by the addition of sarco-endoplasmic reticulum Ca(2+) ATPase inhibitor thapsigargin (25 nM) or calcium ionophore A23187 (1 microM) in the cultures. The protein synthesis was studied by in vitro metabolic labelling followed by one- and two-dimensional polyacrylamide gel electrophoresis, and mass spectrometry was utilized to confirm the identity of the protein spots on two-dimensional gels. Continuous 30 MPa HP increased remarkably the relative labelling of Hsp70. Labelling of Hsp90 was also increased by 15-20%, although no clear change was evident at the protein level in Western blots. Elevated intracellular Ca(2+) concentration induced by thapsigargin and calcium ionophore A23187 increased mainly the synthesis of glucose-regulated protein 78 (Grp78/BiP), whereas Hsp70 and Hsp90 were decreased by the treatment. Heat shock was the strongest inducer of Hsp70 and Hsp90. This study further confirmed the induction of Hsp70 in chondrocytic cells exposed to high HP, but it also showed that calcium-mediated responses are unlikely to cause the stress response observed in the hydrostatically pressurized cells.
authors.affiliation: Department of Anatomy, University of Kuopio, 70211 Kuopio, Finland.
authors.forename: M A
authors.initials: MA
authors.lastname: Elo
authors.forename: R K
authors.initials: RK
authors.lastname: Sironen
authors.forename: K
authors.initials: K
authors.lastname: Kaarniranta
authors.forename: S
authors.initials: S
authors.lastname: Auriola
authors.forename: H J
authors.initials: HJ
authors.lastname: Helminen
authors.forename: M J
authors.initials: MJ
authors.lastname: Lammi
mesh_terms: D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism; D002460:Cell Line; D019902:Chondrocytes / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006706:Homeostasis; D006358:Hot Temperature; D006801:Humans; D006874:Hydrostatic Pressure; D013058:Mass Spectrometry; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics
chemical_list: D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D010446:Peptide Fragments; D002118:Calcium