Abstract
Febrile-range hyperthermia worsens and hypothermia mitigates lung injury, and temperature dependence of lung injury is blunted by inhibitors of p38 mitogen-activated protein kinase (MAPK). Of the two predominant p38 isoforms, p38α is proinflammatory and p38β is cytoprotective. Here, we analyzed the temperature dependence of p38 MAPK activation, substrate interaction, and tertiary structure. Incubating HeLa cells at 39.5 °C stimulated modest p38 activation, but did not alter tumor necrosis factor-α (TNFα)-induced p38 activation. In in vitro kinase assays containing activated p38α and MAPK-activated kinase-2 (MK2), MK2 phosphorylation was 14.5-fold greater at 39.5 °C than at 33 °C. By comparison, we observed only 3.1- and 1.9-fold differences for activating transcription factor-2 (ATF2) and signal transducer and activator of transcription-1α (STAT1α) and a 7.7-fold difference for p38β phosphorylation of MK2. The temperature dependence of p38α:substrate binding affinity, as measured by surface plasmon resonance, paralleled substrate phosphorylation. Hydrogen-deuterium exchange MS (HDX-MS) of p38α performed at 33, 37, and 39.5 °C indicated temperature-dependent conformational changes in an α helix near the common docking and glutamate:aspartate substrate-binding domains at the known binding site for MK2. In contrast, HDX-MS analysis of p38β did not detect significant temperature-dependent conformational changes in this region. We observed no conformational changes in the catalytic domain of either isoform and no corresponding temperature dependence in the C-terminal p38α-interacting region of MK2. Because MK2 participates in the pathogenesis of lung injury, the observed changes in the structure and function of proinflammatory p38α may contribute to the temperature dependence of acute lung injury.
Highlights
Febrile-range hyperthermia worsens and hypothermia mitigates lung injury, and temperature dependence of lung injury is blunted by inhibitors of p38 mitogen-activated protein kinase (MAPK)
We showed that SB203580, a catalytic inhibitor that only inhibits p38␣ and p38 among the p38 isoforms, reduces the effect of febrile-range hyperthermia (FRH) on TNF␣-induced endothelial leak, neutrophil transendothelial migration, and LPS-induced lung injury [10, 11]
We previously showed that exposure to FRH (ϳ39.5 °C) causes a modest increase in levels of activated p38 MAPK in whole-lung tissue homogenates in mice in vivo [11] and human microvascular lung endothelial cells (HMVECs) in vitro [10, 11]
Summary
Febrile-range hyperthermia worsens and hypothermia mitigates lung injury, and temperature dependence of lung injury is blunted by inhibitors of p38 mitogen-activated protein kinase (MAPK). Because MK2 participates in the pathogenesis of lung injury, the observed changes in the structure and function of proinflammatory p38␣ may contribute to the temperature dependence of acute lung injury. Changes in temperature within this clinically relevant hypo-to-hyperthermia range exert critical biological effects that impact cell survival, endothelial barrier function, coagulation, leukocyte trafficking, and inflammation (8 –15). We showed that SB203580, a catalytic inhibitor that only inhibits p38␣ and p38 among the p38 isoforms, reduces the effect of febrile-range hyperthermia (FRH) on TNF␣-induced endothelial leak, neutrophil transendothelial migration, and LPS-induced lung injury [10, 11]. The nature of substrate-specific interactions with the p38 substrate-docking domains likely determines the phosphorylation efficiency for each substrate and the downstream biological effects
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