TNF receptor I is required for induction of macrophage heat shock protein 70.
Expression of heat shock proteins (HSP) is an adaptive response to cellular stress. Stress induces tumor necrosis factor (TNF)-alpha production. In turn, TNF-alpha induces HSP70 expression. However, osmotic stress or ultraviolet radiation activates TNF-alpha receptor I (TNFR-I) in the absence of TNF-alpha. We postulated that TNF-alpha receptors are involved in the induction of HSP70 by cellular stress. Peritoneal Mphi were isolated from wild-type (WT), TNF-alpha knockout (KO), and TNFR (I or II) KO mice. Cells were cultured overnight and then heat stressed at 43 +/- 0.5 degrees C for 30 min followed by a 4-h recovery at 37 degrees C. Cellular HSP70 expression was induced by heat stress or exposure to endotoxin [lipopolysaccharide (LPS)] as determined by immunoblotting. HSP70 expression induced by either heat or LPS was markedly decreased in TNFR-I KO Mphi, whereas TNFR-II KO Mphi exhibited HSP70 expression comparable to that in WT mice. Expression of HSP70 after heat stress in TNF-alpha KO Mphi was also similar to that in WT mice, suggesting that induction of HSP70 by TNFR-I occurs independently of TNF-alpha. In addition, levels of steady-state HSP70 mRNA were similar by RT-PCR in WT and TNFR-I KO Mphi despite differences in protein expression. Furthermore, the effect of TNFR-I appears to be cell specific, since HSP70 expression in splenocytes isolated from TNFR-I KO was similar to that in WT splenocytes. These studies demonstrate that TNFR-I is required for the synthesis of HSP70 in stressed Mphi by a TNF-independent mechanism and support an intracellular role for TNFR-I.
Heimbach
J K
JK
Department of Surgery, University of Colorado Health Sciences Center, Denver, Colorado, 80262, USA. julie.heimbach@uchsc.edu
Reznikov
L L
LL
Calkins
C M
CM
Robinson
T N
TN
Dinarello
C A
CA
Harken
A H
AH
Meng
X
X
D000818:Animals; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D006358:Hot Temperature; D015151:Immunoblotting; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D012313:RNA / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics / Q000378:metabolism*; D013154:Spleen / Q000166:cytology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*
D018840:HSP70 Heat-Shock Proteins; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D012313:RNA