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Novel GRK and β‐arrestin isotype regulation of Toll‐like receptor 4 signaling
Author(s) -
Grisanti Laurel,
Porter James E
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1007.2
Subject(s) - microbiology and biotechnology , p38 mitogen activated protein kinases , rna interference , toll like receptor , small interfering rna , signal transduction , tlr4 , phosphorylation , biology , lipopolysaccharide , receptor , chemistry , rna , mapk/erk pathway , endocrinology , biochemistry , gene , innate immune system
Adrenergic receptors (ARs) are expressed on immune cell populations, but their precise function is not known. We have shown that α 1B AR stimulation synergistically increases IL‐1β release from lipopolysaccharide (LPS)‐challenged human monocytes through an NFκB‐independent, but p38/AP‐1‐dependent mechanism. RNA interference (RNAi) for β‐arrestin (βARR) 1 prevented α 1B AR mediated increases in LPS‐induced IL‐1β production. We hypothesized that concurrent α 1B AR and TLR4 activation leads to increased IL‐1β levels through βARR1‐dependent activation of p38. We demonstrate using RNAi that βARR2 but not βARR1 is necessary for p38 phosphorylation in monocytes concomitantly treated with phenylephrine (PE) and LPS. Co‐immunoprecipitation and confocal microscopy techniques, showed that MEK3/6 interacts with βARR2, promoting activation of p38. Electrophoretic mobility shift assays (EMSA) demonstrated the importance of βARR2 for AP‐1 activation and inhibition of the NFκB pathway after PE and LPS treatment. Using RNAi we showed the necessity of GRK2 for α 1B AR modulation of LPS‐mediated IL‐1β generation, while GRK5 inhibited production of IL‐1β in response to both PE plus LPS and LPS only treatments. This study demonstrates that βARR1 and 2 serve unique functions and provides direct evidence for GRK2/βARR2‐dependent activation of p38, as well as a novel βARR2‐dependent inhibition of NFκB in human monocytes.