CYSTEINE-RICH FGF RECEPTOR REGULATES INTRACELLULAR FGF-1 AND FGF-2 LEVELS

The cysteine-rich FGF receptor (CFR) is a 150-kD membrane-associated g lycoprotein that specifically binds FGFs. CFR protein is not detectabl e at the cell surface and immunocytochemistry with anti-CFR antibodies demonstrates that CFR is concentrated in the Golgi apparatus. These d ata suggest CFR does not function as a plasma membrane FGF receptor. C FR expressed in chinese hamster ovary cells reduces the intracellular accumulation of exogenously applied FGF-1 and FGF-2. A mutant CFR lack ing the juxtamembrane, transmembrane and intracellular domains is unab le to alter intracellular FGF levels. Mutant CFR is detected throughou t the cell, indicating that the domains absent in mutant CFR are requi red for appropriate subcellular localization and the regulation of int racellular FGF levels. Although the activation of plasma membrane rece ptors is necessary for cellular responses to FGFs, a requirement for i ntracellular FGF has also been proposed. The subcellular localization of CFR and its ability to regulate the levels of intracellular FGFs su ggests that CFR may be involved in intracellular FGF trafficking and t he regulation of cellular responses to FGFs. (C) 1997 Wiley-Liss, Inc.