Unconventional secretion: an extracellular trap for export of fibroblast growth factor 2.
Several secretory proteins are released from cells by mechanisms that are distinct from the classical endoplasmic reticulum (ER)/Golgi-mediated secretory pathway. Recent studies unexpectedly revealed that the interaction between one such protein, fibroblast growth factor 2 (FGF-2), and cell surface heparan sulfate proteoglycans (HSPGs) is essential for secretion. FGF-2 mutants that cannot bind to heparan sulfates are not secreted, and cells that do not express functional HSPGs cannot secrete wild-type FGF-2. FGF-2 appears to be secreted by direct translocation across the plasma membrane in an ATP- and membrane-potential-independent manner. I propose that its translocation across the membrane is a diffusion-controlled process in which cell surface HSPGs function as an extracellular molecular trap that drives directional transport of FGF-2.
Nickel
Walter
W
Heidelberg University Biochemistry Center (BZH), Im Neuenheimer Feld 328, 69120 Heidelberg, Germany. walter.nickel@bzh.uni-heidelberg.de
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism*; D019812:Heparan Sulfate Proteoglycans / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D008954:Models, Biological; D021381:Protein Transport
D019812:Heparan Sulfate Proteoglycans; D016222:Fibroblast Growth Factor 2