Identification of SH3 domain interaction partners of human FasL (CD178) by phage display screening.
BACKGROUND
Fas ligand is a cytotoxic effector molecule of T and NK cells which is characterized by an intracellular N-terminal polyproline region that serves as a docking site for SH3 and WW domain proteins. Several previously described Fas ligand-interacting SH3 domain proteins turned out to be crucial for the regulation of storage, expression and function of the death factor. Recent observations, however, indicate that Fas ligand is also subject to posttranslational modifications including shedding and intramembrane proteolysis. This results in the generation of short intracellular fragments that might either be degraded or translocate to the nucleus to influence transcription. So far, protein-protein interactions that specifically regulate the fate of the intracellular fragments have not been identified.


RESULTS
In order to further define the SH3 domain interactome of the intracellular region of Fas ligand, we now screened a human SH3 domain phage display library. In addition to known SH3 domains mediating binding to the Fas ligand proline-rich domain, we were able to identify a number of additional SH3 domains that might also associate with FasL. Potential functional implications of the new binding proteins for the death factor's biology are discussed. For Tec kinases and sorting nexins, the observed interactions were verified in cellular systems by pulldown experiments.


CONCLUSIONS
We provide an extended list of putative Fas ligand interaction partners, confirming previously identified interactions, but also introducing several novel SH3 domain proteins that might be important regulators of Fas ligand function.
Voss
Matthias
M
Institute of Immunology, Christian-Albrechts-University of Kiel, D-24105 Kiel, Germany. matthias.voss@med.uni-muenchen.de
Lettau
Marcus
M
Janssen
Ottmar
O
D021581:Active Transport, Cell Nucleus; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D003001:Cloning, Molecular; D053222:Fas Ligand Protein / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D019151:Peptide Library; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs / Q000235:genetics; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D058305:Sorting Nexins; D033921:Vesicular Transport Proteins / Q000378:metabolism; D018909:src Homology Domains / Q000235:genetics
D002352:Carrier Proteins; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D010446:Peptide Fragments; D019151:Peptide Library; D011993:Recombinant Fusion Proteins; D058305:Sorting Nexins; D033921:Vesicular Transport Proteins; C089848:Tec protein-tyrosine kinase; D011505:Protein-Tyrosine Kinases