Journal of cellular physiology
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G-protein-coupled receptor kinase 2 (GRK2) is a member of a kinase family originally discovered for its role in the phosphorylation and desensitization of G-protein-coupled receptors. It is expressed in high levels in myeloid cells and its levels are altered in many inflammatory disorders including sepsis. To address the physiological role of myeloid cell-specific GRK2 in inflammation, we generated mice bearing GRK2 deletion in myeloid cells (GRK2▵mye). ⋯ Our results further identify TLR4-induced NF-κB1p105-ERK pathway to be selectively regulated by GRK2. LPS-induced activation of NF-κB1p105-MEK-ERK pathway is significantly enhanced in the GRK2▵mye macrophages compared to GRK2fl/fl cells and importantly, inhibition of the p105 and ERK pathways in the GRK2▵mye macrophages, limits the enhanced production of LPS-induced cytokines/chemokines. Taken together, our studies reveal previously undescribed negative regulatory role for GRK2 in TLR4-induced p105-ERK pathway as well as in the consequent inflammatory cytokine/chemokine production and endotoxemia in mice.
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Malignant mesothelioma is an aggressive tumor of serosal surfaces, which is refractory to current treatment options. Arsenic trioxide (As2O3) is used clinically to treat acute promyelocytic leukemia, and also to inhibit proliferation of several solid tumors including hepatoma, esophageal, and gastric cancer in vitro. Here we found that As2O3 inhibited cell viability of a mesothelioma cell line, NCI-H2052. ⋯ Moreover, JNK1 siRNA, but not JNK2 siRNA, abrogated As2O3-induced ERK1/2 phosphorylation. JNK2 siRNA together with PD98059, a specific MAPK/ERK kinase inhibitor, suppressed As2O3-induced apoptosis more significantly than JNK2 siRNA alone. These results indicated that As2O3 induces apoptosis of NCI-H2052 cells mainly through JNK1/2 activation, and that ERK1/2 is involved in As2O3-induced apoptosis when JNK1/2 are inactivated.