Abstract: | FGF2 is a cell survival factor involved in tumor-induced angiogenesis that is secreted through an unconventional secretory
pathway based upon direct protein translocation across the plasma membrane. Here, we demonstrate that both PI(4,5)P2-
dependent FGF2 recruitment at the inner plasma membrane leaflet and FGF2 membrane translocation into the extracellular
space are positively modulated by cholesterol in living cells. We further revealed cholesterol to enhance FGF2 binding to
PI(4,5)P2-containing lipid bilayers. Based on extensive atomistic molecular dynamics (MD) simulations and membrane tension
experiments, we proposed cholesterol to modulate FGF2 binding to PI(4,5)P2 by (i) increasing head group visibility of PI(4,5)P2
on the membrane surface, (ii) increasing avidity by cholesterol-induced clustering of PI(4,5)P2 molecules triggering FGF2
oligomerization, and (iii) increasing membrane tension facilitating the formation of lipidic membrane pores. Our findings have
general implications for phosphoinositide-dependent protein recruitment to membranes and explain the highly selective
targeting of FGF2 toward the plasma membrane, the subcellular site of FGF2 membrane translocation during
unconventional secretion of FGF2. |