Suppressor of IKK epsilon forms direct interactions with cytoskeletal proteins, tubulin and α‐actinin, linking innate immunity to the cytoskeleton

• Published in: FEBS open bio Vol. 8; no. 7; pp. 1064 - 1082
• Main Authors: Sonnenschein, Halie A., Lawrence, Kenneth F., Wittenberg, Karli A., Slykas, Frank A., Dohleman, Emerald L., Knoublauch, Jilan B., Fahey, Sean M., Marshall, Timothy M., Marion, James D., Bell, Jessica K.
• Format: Journal Article
• Language: English
• Published: Amsterdam John Wiley & Sons, Inc 01.07.2018
• Subjects: Actin; Actinin; Affinity; Apoptosis; Cell adhesion & migration; Cell cycle; Cell migration; CRISPR; Cytoskeleton; Enzymes; Epithelial cells; Experiments; Ezrin; Immune system; Immunofluorescence; Immunoprecipitation; Innate immunity; Insects; Interferon; Kinases; Mass spectroscopy; Myeloid cells; Pathogens; Phosphatase; Phosphorylation; Protein purification; Proteins; Proteomics; RNA polymerase; Tubulin
• ISSN: 2211-5463; 2211-5463
• DOI: 10.1002/2211-5463.12454

Suppressor of IKK epsilon ( SIKE ) is associated with the type I interferon response of the innate immune system through TANK ‐binding kinase 1 ( TBK 1). Originally characterized as an endogenous inhibitor of TBK 1 when overexpressed in viral infection and pathological cardiac hypertrophic models, a mechanistic study revealed that SIKE acts as a high‐affinity substrate of TBK 1, but its function remains unknown. In this work, we report that scratch assay analysis of parental and SIKE CRISPR /Cas9 knockout HAP 1 cells showed an ~ 20% decrease in cell migration. Investigation of the SIKE interaction network through affinity purification/mass spectrometry showed that SIKE formed interactions with cytoskeletal proteins. In immunofluorescence assays, endogenous SIKE localized to cytosolic puncta in both epithelial and myeloid cells and to nuclear puncta in myeloid cells, while in epithelial cells additional staining occurred in stress fiber‐like structures and adjacent to the plasma membrane. Using cellular markers, co‐occurrence of SIKE fluorescence with actin, α‐actinin, and ezrin was detected. Reciprocal immunoprecipitation revealed a SIKE :tubulin interaction sensitive to the phosphorylation state of SIKE , but a SIKE :α‐actinin interaction was unchanged by SIKE phosphorylation. In vitro precipitation assays confirmed a direct SIKE interaction with tubulin and α‐actinin. These results indicate that SIKE may promote cell migration by directly associating with the cytoskeleton. In this role, SIKE may mediate cytoskeletal rearrangement necessary in innate immunity, but also link a key catalytic hub, TBK 1, to the cytoskeleton. Database The mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium via the PRIDE [1] partner repository with the dataset identifier  PXD 007262.