RESUMO
Human group IIA secreted phospholipase A2 (hGIIA) promotes tumor growth and inflammation and can act independently of its well described catalytic lipase activity via an alternative poorly understood signaling pathway. With six chemically diverse inhibitors we show that it is possible to selectively inhibit hGIIA signaling over catalysis, and x-ray crystal structures illustrate that signaling involves a pharmacologically distinct surface to the catalytic site. We demonstrate in rheumatoid fibroblast-like synoviocytes that non-catalytic signaling is associated with rapid internalization of the enzyme and colocalization with vimentin. Trafficking of exogenous hGIIA was monitored with immunofluorescence studies, which revealed that vimentin localization is disrupted by inhibitors of signaling that belong to a rare class of small molecule inhibitors that modulate protein-protein interactions. This study provides structural and pharmacological evidence for an association between vimentin, hGIIA, and arachidonic acid metabolism in synovial inflammation, avenues for selective interrogation of hGIIA signaling, and new strategies for therapeutic hGIIA inhibitor design.
Assuntos
Ácido Araquidônico/metabolismo , Artrite Reumatoide/metabolismo , Inibidores Enzimáticos/farmacologia , Fosfolipases A2 do Grupo II/antagonistas & inibidores , Transdução de Sinais/efeitos dos fármacos , Membrana Sinovial/metabolismo , Vimentina/metabolismo , Animais , Ácido Araquidônico/genética , Artrite Reumatoide/tratamento farmacológico , Artrite Reumatoide/genética , Artrite Reumatoide/patologia , Células CHO , Cricetinae , Cricetulus , Desenho de Fármacos , Inibidores Enzimáticos/uso terapêutico , Feminino , Fosfolipases A2 do Grupo II/genética , Fosfolipases A2 do Grupo II/metabolismo , Humanos , Masculino , Transdução de Sinais/genética , Membrana Sinovial/patologia , Vimentina/genéticaRESUMO
MSI1-like WD40 repeat proteins are subunits of many protein complexes controlling chromatin dynamics. These proteins do not have any catalytic activity, but several recent studies using loss-of-function mutants established specific functions during development. Here, we review the current knowledge of MSI1-like proteins, including their phylogenetic history, expression patterns, biochemical interactions and mutant phenotypes. MSI1-like proteins, which are often targets or partners of tumor-suppressor proteins, are required during cell proliferation and differentiation in flies, nematodes and plants. We discuss the possibility that MSI1-like proteins could function to maintain epigenetic memory during development by targeting silencing complexes to chromatin during nucleosome assembly.