TI  - Characterization of  <prot>Fas</prot>  (<prot>Apo-1</prot>, <prot>CD95</prot>)- <prot><prot>Fas</prot> ligand</prot>  interaction.
PG  - 18827-33
AB  - The death-inducing receptor  <prot>Fas</prot>  is activated when cross-linked by the type
      II membrane protein  <prot><prot>Fas</prot> ligand</prot> (<prot>FasL</prot>) . When human soluble <prot>FasL</prot> (sFasL,
      containing the extracellular portion) was expressed in human embryo kidney
      293 cells, the three N-linked glycans of each <prot>FasL</prot> monomer were found to
      be essential for efficient secretion. Based on the structure of the
      closely related <prot>lymphotoxin alpha</prot>-<prot>tumor necrosis factor receptor I</prot>
      complex, a molecular model of the     <prot>FasL</prot>     homotrimer bound to three  <prot>Fas</prot> 
      molecules was generated using knowledge-based protein modeling methods.
      Point mutations of amino acid residues predicted to affect the
      receptor-ligand interaction were introduced at three sites. The F275L
      mutant, mimicking the loss of function murine gld mutation, exhibited a
      high propensity for aggregation and was unable to bind to <prot>Fas</prot>. Mutants
      P206R, P206D, and P206F displayed reduced cytotoxicity toward <prot>Fas</prot>-positive
      cells with a concomitant decrease in the binding affinity for the
      recombinant <prot>Fas</prot>-immunoglobulin Fc fusion proteins. Although the cytotoxic
      activity of mutant Y218D was unaltered, mutant Y218R was inactive,
      correlating with the prediction that Tyr-218 of <prot>FasL</prot> interacts with a
      cluster of three basic amino acid side chains of <prot>Fas</prot>. Interestingly,
      mutant Y218F could induce apoptosis in murine, but not human cells.
AD  - Institute of Biochemistry, University of Lausanne, BIL Biomedical Research
