Structural modeling of cytokine-receptor-JAK2 signaling complexes using AlphaFold Multimer

Area of Science:

• Biochemistry and Molecular Biology
• Cellular Signaling
• Structural Biology

Background:

• Class 1 cytokine receptors (EPOR, TPOR, CSF3R, GHR, PRLR) are single-pass transmembrane glycoproteins regulating crucial cellular processes.
• These receptors, upon ligand binding, form active signaling complexes with Janus Kinase 2 (JAK2).
• Limited structural information exists for complete transmembrane (TM) receptor-cytokine-JAK2 complexes, hindering understanding of JAK-STAT pathway activation.

Approach:

• Generated three-dimensional models of five human receptor complexes with cytokines and JAK2 using AlphaFold Multimer.
• Employed a stepwise assembly strategy for large complexes (3220–4074 residues), validating models against experimental data.
• Equilibrated models in explicit plasma membrane lipids for dynamic simulations.

Key Points:

• Proposed a general activation mechanism involving ligand-induced receptor dimerization and TM α-helix rotation, leading to JAK2 activation.
• Provided a potential binding mode for eltrombopag to the thrombopoietin receptor (TPOR) TM helices.
• Offered insights into the molecular basis of oncogenic mutations, including potential non-canonical activation routes.

Conclusions:

• The generated models provide a structural basis for understanding class 1 cytokine receptor activation and JAK-STAT signaling.
• These models facilitate the study of oncogenic mutations and drug interactions.
• Publicly available models support further research into receptor structure-function relationships and therapeutic target identification.