Characterization of the murine BEK fibroblast growth factor (FGF) receptor: activation by three members of the FGF family and requirement for heparin.

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The bek gene encodes a member of the high-affinity fibroblast growth factor receptor family. The BEK/FGFR-2 receptor is a membrane-spanning tyrosine kinase with the typical features of FGF receptors. We have cloned a murine bek cDNA and expressed it in receptor-negative Chinese hamster ovary cells and in 32D myeloid cells. The BEK receptor expressed in Chinese hamster ovary cells binds acidic FGF, basic FGF, and Kaposi FGF equally well but does not bind keratinocyte growth factor or FGF-5 appreciably. Upon treatment with basic FGF or Kaposi FGF, the BEK receptor is phosphorylated and a mitogenic response is achieved. Heparan sulfate proteoglycans have been shown to play an obligate role in basic FGF binding to the high-affinity FLG receptor. Unlike the BEK-expressing Chinese hamster ovary cells, 32D cells expressing the BEK receptor require the addition of exogenous heparin in order to grow in the presence of basic FGF or Kaposi FGF. We show that the addition of heparin greatly enhances the binding of radio-labeled basic FGF to the receptor. Thus the BEK receptor, like FLG, also requires an interaction with heparan sulfate proteoglycans to facilitate binding to its ligands.







Sally A. Kornbluth

Jo Rae Wright University Distinguished Professor Emerita

Our lab studies the regulation of complex cellular processes, including cell cycle progression and programmed cell death (apoptosis). These tightly orchestrated processes are critical for appropriate cell proliferation and cell death, and when they go awry can result in cancer and degenerative disorders. Within these larger fields, we have focused on understanding the cellular mechanisms that prevent the onset of mitosis prior to the completion of DNA replication, the processes that prevent cell division when the mitotic spindle is disrupted, the signaling pathways that prevent apoptotic cell death in cancer cells and the mechanisms that link cell metabolism to cell death and survival.

In our quest to answer these important cell biological and biochemical questions, we are varied in our use of experimental systems.   Traditionally, we have used cell-free extracts prepared from eggs of the frog Xenopus laevis which can recapitulate cell cycle events and apoptotic processes in vitro. For the study of cell cycle events, extracts are prepared which can undergo multiple rounds of DNA replication and mitosis in vitro. Progression through the cell cycle can be monitored by microscopic observation of nuclear morphology and by biochemically assaying the activity of serine/threonine kinases which control cell cycle transitions.

For the study of apoptosis, modifications in extract preparation have allowed us to produce extracts which can apoptotically fragment nuclei and can accurately reproduce the biochemical events of apoptosis, including internucleosomal DNA cleavage and activation of apoptotic proteases, the caspases.

More recently, we have focused on studying apoptosis and cell cycle progression in mammalian models, both tissue culture cells and mouse models of cancer.  In these studies, we are trying to determine the precise signaling mechanisms used by cancer cells to accelerate proliferation and evade apoptotic cell death mechanisms.   We also endeavor to subvert these mechanisms to therapeutic advantage.   We are particularly interested in links between metabolism and cell death, as high metabolic rates in cancer cells appear to suppress apoptosis to evade chemotherapy-induced cell death.

Finally, we also have several projects using the facile genetics of Drosophila melanogaster to further understand links between metabolism and cell death and also the ways in which mitochondrial dynamics are linked to apoptotic pathways.

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