Disulfide bridge-dependent dimerization triggers FGF2 membrane translocation into the extracellular space

• DOI: 10.7554/elife.88579
• Publication Date: 2023-05-31T14:43:32Z
• Authors: Fabio Lolicato; Julia P Steringer; Roberto Saleppico; Daniel Beyer; Jaime Fernandez-S...; Sebastian Unger; Steffen Klein; Petra Riegerová; Sabine Wegehingel; Hans-Michael Müller; Xiao J Schmitt; Shreyas Kaptan; Christian Freund; Martin Hof; Radek Šachl; Petr Chlanda; Ilpo Vattulainen; Walter Nickel
• Keywords: Cell membrane

Fibroblast growth factor 2 (FGF2) exits cells by direct translocation across the plasma membrane, a type I pathway of unconventional protein secretion. This process is initiated phosphatidylinositol-4,5-bisphosphate (PI(4,5)P )-dependent formation highly dynamic FGF2 oligomers at inner membrane leaflet, inducing lipidic pores. Cell surface heparan sulfate chains linked to glypican-1 (GPC1) capture outer completing into extracellular space. While basic steps this are well understood, molecular mechanism which oligomerizes on surfaces remains unclear. In current study, we demonstrate initial step depend C95-C95 disulfide-bridge-mediated dimerization surfaces, producing building blocks for higher that drive We find with C95A substitution be defective in oligomerization, pore formation, and translocation. Consistently, variant characterized severe secretion phenotype. By contrast, while also important efficient from cells, second cysteine residue (C77) not involved oligomerization. Rather, C77 part interaction interface through binds α1 subunit Na,K-ATPase, landing platform leaflet. Using cross-linking mass spectrometry, atomistic dynamics simulations combined machine learning analysis cryo-electron tomography, propose disulfide-bridged dimers bind high avidity PI(4,5)P surfaces. further tight coupling between ternary signaling complexes cell hypothesizing C95-C95-bridged functioning as units triggering autocrine paracrine signaling.