Acidic extracellular environment induces only a subset of heat-shock proteins in primary mouse kidney cell cultures

Exposure of primary mouse kidney cell cultures to acidic medium (pH 5.5) induced the expression of a 70 kilodalton (kDa) protein. This protein was identified as the major inducible heat-shock protein 70 (hsp70) by immunoprecipitation with anti-hsp70 serum and Northern blot analysis with a hsp70 cDNA probe. Maximum induction of the 70-kDa protein at pH 5.5 after 240 min was about 30% of that observed after 60 min of thermal treatment at 43 degrees C. In addition, there was an apparent induction of the glucose-regulated proteins (GRPs) of 76-78 and 98-100 kDa, but not of the other hsps. This subset induction of the heat-shock response by acidic medium suggests that different mechanisms are responsible for the induction of the various families of hsps.