Lagaudriere-Gesbert, C. | bioRxiv Science

bioRxiv2025

NAP1 switches from an activator to a limiter of interferon induction by trapping TBK1 in condensates

TBK1 kinase is a central regulator of type I IFN production. Upon activation of the IFN-{beta} induction pathway, TBK1-adaptor proteins (NAP1, SINTBAD, TANK) form condensates with liquid properties. We showed that NAP1 condensates concentrate TBK1. Using NAP1KO cell lines, we discovered that NAP1 exerts a dual effect on TBK1 activity. Initially, NAP1 binds TBK1 and increases its activity, which enhances the activation of the IFN pathway. Then, phosphorylation of NAP1 by TBK1 induces the formation of NAP1 condensates. These condensates concentrate TBK1 and PP2A, a phosphatase known to dephosphorylate and consequently deactivate TBK1, thus limiting IFN induction. Additionally, in patients with lupus or interferonopathies, we identified NAP1 variants, unable to form condensates upon cell exposure to danger signals, which can only activate TBK1 without limiting its activity. This study reveals an original mode of regulating a signaling pathway by formation of condensates and provides a molecular explanation for certain interferonopathies.

immunology↗

bioRxiv2024

Optimization of the VSV G backbone for amino terminal fusion with nanobodies allowing its retargeting to receptors of therapeutic interest.

Vesicular stomatitis virus (VSV) is a promising oncolytic virus. Additionally, its glycoprotein G is the most commonly used envelope glycoprotein to pseudotype lentiviral vectors for gene therapy. However, G receptors (LDLR family members) are ubiquitous and expressed at the surface of non-target cells, precluding in vivo gene therapy. Recently, we identified G mutants that no longer bind to LDLR but retain their fusion activity. This opened the possibility of specifically retargeting the glycoprotein to receptors of interest. Here, we constructed chimeric glycoproteins fused with a nanobody at the amino-terminus of G. By experimental evolution, we identified two mutations in G improving the folding and functionality of chimeric Gs, regardless of the nanobody inserted at the amino-terminus. We then constructed chimeric glycoproteins using several nanobodies targeting HER2 receptor and, into these chimeras, we introduced mutations that abolish the recognition of LDL receptors. VSV and lentiviruses pseudotyped with these glycoproteins specifically infect cells expressing HER2. We have therefore identified G mutations that optimize the G scaffold to tolerate amino-terminal insertion of a nanobody and establish proof of concept that this approach can be used to confer a new tropism on G. This paves the way for targeted in vivo therapies.

bioengineering↗