Biology subjects

Thomsen, A.

Publications and source records attributed to Thomsen, A..

3 recordsLinked to original sources

bioRxiv2026

A conserved hydrophobic interaction governs GPCR-transducer association

A central feature of G protein-coupled receptor (GPCR) desensitization is the direct competition between heterotrimeric G proteins and {beta}-arrestins ({beta}arrs) for an overlapping binding site within the intracellular receptor cavity. Although numerous high-resolution structures of GPCR-transducer complexes exist, the exact nature of this shared site and the molecular basis of transducer competition remain unclear. To investigate this, we employed an interdisciplinary approach integrating systemic mutational mapping, bioinformatics, and structural analysis across multiple classes of GPCRs and their transducers and regulators. We identified two highly conserved leucine residues within both the {beta}arr finger loop and the G C-terminal -helix, which engage a hydrophobic patch on GPCRs formed by TM3, TM5, and TM6 in a nearly identical manner, thereby stabilizing the complexes. Notably, the GPCR kinase N-terminal -helix also contains hydrophobic residues that associate with this same receptor patch and are vital for the GPCR-GRK engagement. Our findings reveal a conserved hydrophobic interface that mediates direct competition among GPCR transducers and regulators suggesting a universal mechanism that governs receptor access and desensitization.

biochemistry↗

bioRxiv2025

NKCC1 a Regulator of Glioblastoma Progression

Glioblastoma (GBM) is the most common and aggressive primary brain tumor in adults, with poor prognosis despite multimodal therapy. Chloride cotransporters NKCC1 and KCC2 are key regulators of intracellular chloride levels and thereby determine whether GABA acts inhibitory or excitatory. In GBM, disrupted chloride homeostasis promotes proliferation, migration, and stem-like properties, but its clinical relevance is not fully understood. We analysed NKCC1 and KCC2 expression in glioblastoma samples, considering clinical parameters such as age, gender, and MGMT promoter methylation. Statistical analyses included ROC-based cutoff determination, Kaplan-Meier survival analysis and subgroup. Immunohistochemistry was performed to identify cell types expressing NKCC1. NKCC1 expression was significantly higher in older patients and emerged as a prognostic marker for recurrence-free survival, with lower levels correlating with delayed recurrence, although overall survival was unaffected. NKCC1 was expressed in stem-like, astrocytic, and progenitor cells, but not in mature neurons. These findings identify NKCC1 as a regulator of GBM progression and recurrence, linking chloride transporter imbalance to GABAergic signalling. Targeting NKCC1 and restoring chloride homeostasis may provide promising new treatment strategies. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=89 SRC="FIGDIR/small/677289v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@a964f1org.highwire.dtl.DTLVardef@1224400org.highwire.dtl.DTLVardef@9e5c94org.highwire.dtl.DTLVardef@d0324f_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

Plasma membrane rather than endosomal Gq signaling drives transcriptional activity by the viral chemokine receptor US28 in glioblastoma

US28 is a human cytomegalovirus-encoded chemokine receptor homologue that has high agonist-independent activity, internalizes constitutively, and plays an oncomodulatory role in glioblastoma. As G protein signaling was originally believed to strictly occur at the plasma membrane, it has been assumed that US28s constitutive Gq/11 signaling is mediated by a minor population at the plasma membrane. However, accumulating evidence shows that some GPCRs activate G proteins from intracellular organelles, such as endosomes. Importantly, endosomal rather than plasma membrane G protein signaling has been associated with transcriptional activity. Here, we demonstrate that the endosomal US28 population robustly activates Gq/11, and thus, provides the major contribution of Gq/11 signaling. Surprisingly, US28 signaling at the plasma membrane rather than from endosomes primarily drives upregulation of gene expression involved in cell proliferation and inflammatory responses that are associated with glioblastoma and cancer. Our findings highlight the crucial role of receptor signaling location in cellular responses.

cell biology↗