Shedding of membrane vesicles mediates fibroblast growth factor-2 release from cells.
Fibroblast growth factor-2 (FGF-2), a polypeptide with regulatory activity on cell growth and differentiation, lacks a conventional secretory signal sequence, and its mechanism of release from cells remains unclear. We characterized the role of extracellular vesicle shedding in FGF-2 release. Viable cells released membrane vesicles in the presence of serum. However, in serum-free medium vesicle shedding was dramatically down-regulated, and the cells did not release FGF-2 activity into their conditioned medium. Addition of serum to serum-starved cells rapidly induced intracellular FGF-2 clustering under the plasma membrane and into granules that colocalized with patches of the cell membrane with typical features of shed vesicle membranes. Shed vesicles carried three FGF-2 isoforms (18, 22, 24 kDa). Addition of vesicles to endothelial cells stimulated chemotaxis and urokinase plasminogen activator production, which were blocked by anti-FGF-2 antibodies. Treatment of intact vesicles with 2.0 m NaCl or heparinase, which release FGF-2 from membrane-bound proteoglycans, did not abolish their stimulatory effect on endothelial cells, indicating that FGF-2 is carried inside vesicles. The comparison of the stimulatory effects of shed vesicles and vesicle-free conditioned medium showed that vesicles represent a major reservoir of FGF-2. Thus, FGF-2 can be released from cells through vesicle shedding.
Taverna
Simona
S
Dipartimento Biologia Cellulare e dello Sviluppo, Università di Palermo, Palermo 90128, Italy.
Ghersi
Giulio
G
Ginestra
Angela
A
Rigogliuso
Salvatrice
S
Pecorella
Sonia
S
Alaimo
Giovanna
G
Saladino
Francesca
F
Dolo
Vincenza
V
Dell'Era
Patrizia
P
Pavan
Antonio
A
Pizzolanti
Giuseppe
G
Mignatti
Paolo
P
Presta
Marco
M
Vittorelli
Maria Letizia
ML
D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000502:physiology*; D016895:Culture Media, Serum-Free; D042783:Endothelial Cells; D016222:Fibroblast Growth Factor 2 / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008856:Microscopy, Fluorescence; D020033:Protein Isoforms; D022142:Secretory Vesicles; D044967:Serum
D016895:Culture Media, Serum-Free; D020033:Protein Isoforms; D016222:Fibroblast Growth Factor 2