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

Abstract

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.

Pooled analysis of radiation hybrids identifies loci for growth and drug action in mammalian cells

“…Similarly, FSIP1 regulates growth of triple-negative breast cancer cells and also resistance to docetaxel, a drug in the same class as paclitaxel (Liu, Sun, et al 2018). SIKE1 (Sonnenschein et al 2018) and CPT1A (Li, Zhao, et al 2013) also regulated both cell growth and microtubule activity. The interaction genes may thus provide useful clues to the relationship between growth inhibition and paclitaxel action ( Supporting Information ).…”

Transcriptomic analysis of bovine monocytes in response to non-cytopathic bovine viral diarrhea virus infection

“…However, we observed that type I IFN genes were reduced such as IRF7, DDX3X, DDX58, TLR13, TLR9, STING, and IFIT1, which was possibly caused by the ncp BVDV viral particles [12,13]. On the other hand, upregulated DEGs, such as NLRX1, CYLD, SIKE1, ATG12, and RNF125, were shown to interfere with host immune responses in previous documents [23][24][25][26].…”

“…This study found common groups of genes related to important cellular processes at 2 hpi. For example, inhibition of NF-κB activation was induced by upregulated IKKE and SIKE1, negative regulators of the NF-κB signaling pathway, and by downregulated p65/RelA-NF-κB [26]. These inhibitory actions could lead to blocked or delayed antiviral responses (Table 2).…”

Transcriptomic analysis of bovine monocytes in response to non-cytopathic bovine viral diarrhea virus infection

“…Inhibits TLR3-mediated activation of interferonstimulated response elements (ISRE) and the IFN-beta promoter. May act by disrupting the interactions of IKBKE or TBK1 with TICAM1/TRIF, IRF3 and DDX58/RIG-I [27,28].…”

“…SIKE1, IKK-epsilon, and TBK1 genes are physiological inhibitors that act on viral and TLR3triggered IRF3 to inhibit TLR3-mediated interferon-stimulated response elements (ISRE) and IFN-β promoters. Activation of the ISRE and IFN-β promoters can be achieved by disrupting the interaction between IKBKE or TBK1 and TICAM1/TRIF, IRF3, and DDX58/RIG-I, which does not inhibit the NF-κB activation pathway [27,28].…”