👤 Nicolas Servant

Abdominal aortic aneurysm (AAA) is a serious disease with no effective pharmacological therapy. Although inflammation is recognized as a key regulator of AAA, targeting inflammatory pathways once the disease is established does not improve outcomes. Understanding the earliest molecular indicators could clarify precise biological targets and prognostic markers for AAA. Using ApoE-deficient mice, we performed RNA-Seq on suprarenal abdominal aortas (SRAs) from Ang II- and saline-treated mice 24 h after infusion. We further developed a unique model of hyperlipidemic mice in which the expression of the inhibitor of nuclear factor kappa B kinase subunit beta (IKKβ) can be conditionally suppressed in vascular smooth muscle cells (VSMCs). RNA-Seq data revealed early IKKβ-dependent cellular anabolic processes in SRAs, including activation of the mammalian target of rapamycin complex 1 (mTORC1) pathway. Furthermore, deletion of the Show less

G protein-coupled receptors (GPCRs) rapidly transmit extracellular signals by activating effector proteins, thereby producing well-characterized second messenger molecules. Free, unanchored polyubiquitin chains have been proposed as secondary messengers in immune and inflammatory pathways that regulate cellular responses to invading pathogens and the inflammatory cytokine Interleukin-1 beta (IL-1β). It remains unknown whether these molecules play a role in GPCR signaling. The present study used primary, immortalized, and transformed cellular models, together with loss-of-function approaches, to demonstrate the presence and functions of unanchored polyubiquitin chains in inflammatory signaling pathways that activate the activator protein 1 (AP-1) and nuclear factor-kappa B (NF-κB) transcription factors. In response to inflammatory GPCR agonists Angiotensin II (Ang II), lysophosphatidic acid (LPA), and thrombin (Thr), the E3 ubiquitin ligase tumor necrosis factor receptor-associated factor 6 (TRAF6) controls early signaling events that lead to T-loop phosphorylation of Transforming Growth Factor β-activated kinase 1 (TAK1), IκB kinase beta (IKKβ), c-Jun N-terminal kinases (JNK1/2), and p38 mitogen-activated protein kinases (p38). In parallel, we document the rapid, transient TRAF6-dependent production of unanchored lysine (K)63-linked polyubiquitin chains that accumulate in TAK1 and IKKβ immunocomplexes. Pull-down assays specifically designed to capture unanchored polyubiquitin chains in cellular extracts from stimulated cells further support their transient nature. Lastly, stable expression of a zinc finger ubiquitin-binding protein (ZnF-UBP) domain, which specifically binds unanchored polyubiquitin chains in immortalized keratinocytes exposed to LPA and Thr, shows that this production occurs in the proximity to the plasma membrane and diminishes the T-loop phosphorylation of TAK1, IKKβ, JNK1/2, and p38, thereby affecting the induction of early transcriptional events. Our results support a novel paradigm in GPCR signal transduction, identifying unanchored K63-linked polyubiquitin chains as second messenger molecules. The online version contains supplementary material available at 10.1186/s12964-025-02646-6. Show less

Glioblastoma (GBM) is a highly lethal type of cancer. GBM recurrence following chemoradiation is typically attributed to the regrowth of invasive and resistant cells. Therefore, there is a pressing need to gain a deeper understanding of the mechanisms underlying GBM resistance to chemoradiation and its ability to infiltrate. Using a combination of transcriptomic, proteomic, and phosphoproteomic analyses, longitudinal imaging, organotypic cultures, functional assays, animal studies, and clinical data analyses, we demonstrate that chemoradiation and brain vasculature induce cell transition to a functional state named VC-Resist (vessel co-opting and resistant cell state). This cell state is midway along the transcriptomic axis between proneural and mesenchymal GBM cells and is closer to the AC/MES1-like state. VC-Resist GBM cells are highly vessel co-opting, allowing significant infiltration into the surrounding brain tissue and homing to the perivascular niche, which in turn induces even more VC-Resist transition. The molecular and functional characteristics of this FGFR1-YAP1-dependent GBM cell state, including resistance to DNA damage, enrichment in the G2M phase, and induction of senescence/stemness pathways, contribute to its enhanced resistance to chemoradiation. These findings demonstrate how vessel co-option, perivascular niche, and GBM cell plasticity jointly drive resistance to therapy during GBM recurrence. Show less

GIP-dependent Cushing's syndrome is caused by ectopic expression of glucose-dependent insulinotropic polypeptide receptor (GIPR) in cortisol-producing adrenal adenomas or in bilateral macronodular adrenal hyperplasias. Molecular mechanisms leading to ectopic GIPR expression in adrenal tissue are not known. Here we performed molecular analyses on adrenocortical adenomas and bilateral macronodular adrenal hyperplasias obtained from 14 patients with GIP-dependent adrenal Cushing's syndrome and one patient with GIP-dependent aldosteronism. GIPR expression in all adenoma and hyperplasia samples occurred through transcriptional activation of a single allele of the GIPR gene. While no abnormality was detected in proximal GIPR promoter methylation, we identified somatic duplications in chromosome region 19q13.32 containing the GIPR locus in the adrenocortical lesions derived from 3 patients. In 2 adenoma samples, the duplicated 19q13.32 region was rearranged with other chromosome regions, whereas a single tissue sample with hyperplasia had a 19q duplication only. We demonstrated that juxtaposition with cis-acting regulatory sequences such as glucocorticoid response elements in the newly identified genomic environment drives abnormal expression of the translocated GIPR allele in adenoma cells. Altogether, our results provide insight into the molecular pathogenesis of GIP-dependent Cushing's syndrome, occurring through monoallelic transcriptional activation of GIPR driven in some adrenal lesions by structural variations. Show less