Heme oxygenase is a heat shock protein and PEST protein in rat astroglial cells

Cultured rat forebrain astrocytes contained significant amounts of immunostainable heme oxygenase‐1 (HO‐1) isozyme, whereas HO‐1 was undetectable in spontaneously transformed rat astroglial cells (ATs). HO‐1 was inducible in both cell types by heat shock and by submicromolar amounts of H2O2. Inhibition of RNA synthesis with actinomycin D or protein synthesis with cycloheximide resulted in the rapid loss of immunostainable heme oxygenase in astrocytes. Analysis of the primary structure of heme oxygenase suggests that it is a PEST protein, i.e., targeted for rapid turnover. © 1992 Wiley‐Liss, Inc.