Unpaired cysteine insertions favor transmembrane dimerization and induce ligand-independent constitutive cytokine receptor signaling

Lynn Affrica Felicitas Baumgärtner; Julia Ettich; Helene Balles; Dorothee Johanna Lapp; Sofie Mossner; Christin Bassenge; Meryem Ouzin; Helmut Hanenberg; Jürgen Scheller; Doreen Manuela Floss

doi:10.1515/hsz-2023-0344

Unpaired cysteine insertions favor transmembrane dimerization and induce ligand-independent constitutive cytokine receptor signaling

Biol Chem. 2024 May 3. doi: 10.1515/hsz-2023-0344. Online ahead of print.

Affiliations

¹ Institute of Biochemistry and Molecular Biology II, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, D-40225 Düsseldorf, Germany.
² Department of Otorhinolaryngology and Head/Neck Surgery, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, D-40225 Düsseldorf, Germany.
³ Department of Pediatrics III, University Children's Hospital Essen, University of Duisburg-Essen, D-45122 Essen, Germany.

PMID: 38695485
DOI: 10.1515/hsz-2023-0344

Abstract

Naturally occurring gain-of-function (GOF) mutants have been identified in patients for a variety of cytokine receptors. Although this constitutive activation of cytokine receptors is strongly associated with malignant disorders, ligand-independent receptor activation is also a useful tool in synthetic biology e.g. to improve adoptive cellular therapies with genetically modified T-cells. Balanced Interleukin (IL-)7 signaling via a heterodimer of IL-7 receptor (IL-7Rα) and the common γ-chain (γc) controls T- and B-cell development and expansion, whereas uncontrolled IL-7 signaling can drive acute lymphoid leukemia (ALL) development. The ALL-driver mutation PPCL in the transmembrane domain of IL-7Rα is a mutational insertion of the four amino acids proline-proline-cysteine-leucine and leads to ligand-independent receptor dimerization and constitutive activation. We showed here in the cytokine-dependent pre-B-cell line Ba/F3 that the PPCL-insertion in a synthetic version of the IL-7Rα induced γc-independent STAT5 and ERK phosphorylation and also proliferation of the cells and that booster-stimulation by arteficial ligands additionally generated non-canonical STAT3 phosphorylation via the synthetic IL-7Rα-PPCL-receptors. Transfer of the IL-7Rα transmembrane domain with the PPCL insertion into natural and synthetic cytokine receptor chains of the IL-6, IL-12 and Interferon families also resulted in constitutive receptor signaling. In conclusion, our data suggested that the insertion of the mutated PPCL IL-7Rα transmembrane domain is an universal approach to generate ligand-independent, constitutively active cytokine receptors.

Keywords: gain-of-function receptors; interleukin; receptor homo-dimerization; signal transduction; synthetic receptors.