Biology subjects

Espevik, T.

Publications and source records attributed to Espevik, T..

5 recordsLinked to original sources

bioRxiv2025

Rab11FIP2 controls NLRP3 inflammasome activation through Rab11b

Membrane trafficking through the trans-Golgi network has recently been shown to guide activation of the NLRP3 inflammasome. The GTPases Rab11a and Rab11b, and their effector molecule Rab11-FIP2, are regulators of endosome trafficking and retrograde transport. Rab11-FIP2 binds phosphatidylinositol species including PI4P, enriched in the trans-Golgi network and peripheral endosomes following NLRP3 inflammasome activation. We here demonstrate that Rab11-FIP2 and Rab11b, but not Rab11a, control caspase-1 mediated cleavage of pro-IL-1{beta} and GSDMD, and pyroptotic cell death in human macrophages. Rab11-FIP2 also controlled LPS stimulated IKK{beta} activation by TAK1 and IKK{beta} mediated NLRP3 translocation to the trans-Golgi network. Furthermore, we show that NLRP3 bound Rab11-FIP2 via its KMKK motif and that Rab11-FIP2 interacts with NLRP3 via its N-terminal C2-domain. The formation of PI4P positive endosomes and ASC-specks were also controlled by Rab11-FIP2. Collectively our results demonstrate that Rab11-FIP2 and Rab11b control NLRP3 inflammasome activation on early endosomes in human macrophages.

immunology↗

bioRxiv2025

Novel SLAMF1-derived peptide induces apoptosis in multiple myeloma cells by targeting IRF4 transcription factor for degradation

Multiple myeloma (MM) is the second most common hematological cancer. It remains incurable, highlighting the urgent need for novel therapeutic targets and treatment strategies. In this study, we investigated a panel of peptides derived from a functional motif of Signaling Lymphocytic Activation Molecule Family 1 (SLAMF1) with single amino acid substitutions and found that several of them exhibited potent anti-cancer activity by inducing MM cell death. The most potent peptide P7N4 significantly reduced the viability of both IL-6-dependent and -independent human myeloma cell lines (HMCLs), proteasome inhibitor-resistant MM cells, and primary MM cells, while exerting minimal effects on healthy blood cells. Furthermore, P7N4 enhanced the efficacy of the chemotherapeutic agent melphalan. When combined with the proteasome inhibitor bortezomib, P7N4 potentiated the anti-cancer effect of bortezomib in a highly aggressive murine MM model. Mechanistically, P7N4 induced apoptosis in MM cells by disrupting key pro-survival pathways, leading to reduction in IRF4, MYC, and {beta}-catenin levels, as well as inhibition of Akt and ERK1/2 phosphorylation. Furthermore, in peptide-sensitive HMCL, P7N4 significantly altered the expression of IRF4-associated genes. These effects were likely mediated by direct interaction of peptide with IRF4, targeting this transcription factor for degradation. Overall, our findings established P7N4 as a promising therapeutic candidate for MM, warranting further optimization and in-depth mechanistic studies.

cancer biology↗

bioRxiv2025

A novel TIRAP-MyD88 inhibitor blocks TLR7- and TLR8-induced type I IFN responses

Endosomal toll-like receptors TLR7 and TLR8 are critical sensors of microbial RNA that initiate antiviral and antibacterial immune responses through type I interferon (IFN) and proinflammatory cytokine production. While TIRAP is traditionally associated with plasma membrane TLR signaling, recent evidence suggests it also contributes to signaling via endosomal TLRs. Here, we examined the role of TIRAP in TLR7/8 signaling using P7-Pen, a novel SLAMF1-derived peptide that disrupts the TIRAP-MyD88 interaction. In primary human monocytes and a whole blood model, P7-Pen inhibited TLR7- and TLR8-induced expression and secretion of IRF5-regulated cytokines IFN{beta}, IL-12p40, and IL-12p70, without effect on TNF or IL-6. Mechanistically, P7-Pen blocked TIRAP recruitment to the TLR8-MyD88 complex, leading to reduced late-stage IRAK1 activation, Akt and IKK/{beta} phosphorylation, and downstream IRF5 dimerization and nuclear translocation. Inhibition of Staphylococcus aureus-induced cytokine production by P7-Pen was associated with reduced bacterial phagocytosis, impairing endosomal delivery of bacterial RNA. Notably, P7-Pen failed to inhibit murine TLR7 responses, which correlated with a lack of TIRAP recruitment to MyD88 in mouse macrophages following TLR7 ligand stimulation, highlighting species-specific differences in TLR signaling mechanisms. These findings support a noncanonical role for TIRAP in regulating IRF5-dependent signaling downstream of human TLR7 and TLR8, and demonstrate that selective disruption of TIRAP recruitment by a SLAMF1-derived peptide effectively attenuates IFN{beta} production. This strategy may hold therapeutic potential in diseases characterized by dysregulated type I IFN responses, such as systemic lupus erythematosus and chronic infections.

immunology↗

bioRxiv2024

Raver1 links Ripk1 RNA splicing to caspase-8-mediated pyroptotic cell death, inflammation, and pathogen resistance

Multiple cell death and inflammatory signaling pathways converge on two critical factors: receptor interacting serine/threonine kinase 1 (RIPK1) and caspase-8. Careful regulation of these molecules is critical to control apoptosis, pyroptosis and inflammation. Here we discovered a pivotal role of Raver1 as an essential regulator of Ripk1 pre-mRNA splicing, expression, and functionality, and the subsequent caspase-8-dependent inflammatory cell death. Macrophages from Raver1-deficient mice exhibit altered splicing of Ripk1, accompanied by diminished cell death and reduced activation of caspase-8, Gasdermin D and E, caspase-1, as well as decreased interleukin-18 (IL-18) and IL-1{beta} production. These effects were triggered by Yersinia bacteria, or by restraining TAK1 or IKK{beta} in the presence of LPS, TNF family members, or IFN{gamma}. Consequently, animals lacking Raver1 showed heightened susceptibility to Yersinia infection. Raver1 and RIPK1 also controlled the expression and function of the C-type lectin receptor Mincle. Our study underscores the critical regulatory role of Raver1 in modulating innate immune responses and highlights its significance in directing in vivo and in vitro inflammatory processes. SignificanceCaspase-8 and the kinase RIPK1 are at focal points of several inflammation and cell death pathways. Thus, a careful regulation of their actions is needed. Our work identifies the RNA splicing factor Raver1 as a critical factor directing the splicing of Ripk1 in order to modulate RIPK1/caspase-8-driven pyroptosis, apoptosis and inflammation. Raver1 is central for macrophage responses to Yersinia bacteria, initiated after blockade of kinases TAK1 and IKK, measured as activation of RIPK1, caspase-8, Gasdermin D, caspase-3, IL-1{beta} and IL-18. Importantly, Raver1 is necessary for host resistance to Yersinia infection in vivo. We propose that Raver1 is key for correct tuning of RIPK1-caspase-8 dependent processes.

immunology↗

bioRxiv2022

MultiOMICs landscape of SARS-CoV-2-induced host responses in human lung epithelial cells

Despite the availability of vaccines and approved therapeutics, the COVID-19 pandemic continues to rise owing to the emergence of newer variants. Several multi-omics studies have made available extensive evidence on host-pathogen interactions and potential therapeutic targets. Nonetheless, an increased understanding of host signaling networks regulated by post-translational modifications and their ensuing effect on the biochemical and cellular dynamics is critical to expanding the current knowledge on the host response to SARS-CoV-2 infections. Here, employing unbiased global transcriptomics, proteomics, acetylomics, phosphoproteomics, and exometabolome analysis of a lung-derived human cell line, we show that SARS-CoV-2 Norway/Trondheim-S15 strain induces time-dependent alterations in the induction of type I IFN response, activation of DNA damage response, dysregulated Hippo signaling, among others. We provide evidence for the interplay of phosphorylation and acetylation dynamics on host proteins and its effect on the altered release of metabolites, especially organic acids and ketone bodies. Together, our findings serve as a resource of potential targets that can aid in designing novel host-directed therapeutic strategies.

systems biology↗