Specific induction of heat shock protein 90 beta by high hydrostatic pressure

Abstract

In chondrocytes, a low‐amplitude intermittent hydrostatic pressure induces production of extracellular matrix molecules, while high hydrostatic pressure inhibits it. High pressure increases cellular heat shock protein 70 level in a number of cell types on account of increased stabilisation of the heat shock protein 70 mRNA. In our experiments, only bovine primary chondrocytes, but not an immortalized chondrocytic cell line, could resist the induction of the stress response in the presence of continuous 30 MPa hydrostatic pressure. We have recently shown that protein synthesis is required for the stabilization. According to two‐dimensional gel electrophoresis the synthesis of heat shock protein 90 was also increased in a chondrocytic cell line and in HeLa cells, and mass spectrometric analysis suggested that the induction was rather due to increase in heat shock protein 90β than in heat shock protein 90α. The stress response was rather intense in HeLa cells, therefore, we investigated the effect of continuous 30 MPa hydrostatic pressure on the expression of the two heat shock protein 90 genes in HeLa cells using Northern and Western blot analyses. Heat shock protein 90β mRNA level increased within 6 hours of exposure to 30 MPa hydrostatic pressure, while hsp90α level remained stable. At protein level there was a clear increase in the heat shock protein 90β/heat shock protein 90α ratio, too. These results show a specific regulation of stress proteins in cells exposed to high hydrostatic pressure.