Fig. 6. Model for the dimerization of gp130 and LIFR. According to our data, a large portion of gp130 exists as a transient homodimer in the plasma membrane (a). This preformed homodimer is stabilized upon binding of IL-6/IL-6R
complexes (b). Monomeric gp130 binds IL-6/IL-6R
complexes less efficiently (c) and therefore only marginally contributes to IL-6-signalling. A gp130/LIFR heterodimer is formed mainly in response to LIF stimulation (d).