Interleukin 1 and tumour necrosis factor increase phosphorylation of the small heat shock protein

Abstract

Interleukin 1α and tumour necrosis factor‐α stimulated phosphorylation of three 27 kDa phosphoproteins in MRC‐5 fibroblasts which was sustained for up to 2 h after adding the cytokines. All three phosphoproteins were immunoprecipitated by a specific antiserum to the small mammalian heat shock protein, hsp 27. The three phosphoproteins from stimulated or control cells contained phosphoserine but not phosphothreonine or phosphotyrosine. Similar increases in phosphorylation of immunoprecipitable 27 kDa proteins were seen in U937 cells stimulated by TNFα and Hep G2 cells stimulated by IL 1α.