Association of a novel PDZ domain-containing peripheral Golgi protein with the Q-SNARE (Q-soluble N-ethylmaleimide-sensitive fusion protein (NSF) attachment protein receptor) protein syntaxin 6.
PDZ domains are involved in the scaffolding and assembly of multi-protein complexes at various subcellular sites. We describe here the isolation and characterization of a novel PDZ domain-containing protein that localizes to the Golgi apparatus. Using an in silico cloning approach, we have identified and isolated a cDNA encoding a ubiquitously expressed 59-kDa protein that we call FIG. It is composed of two coiled coil regions, a leucine zipper, and a single PDZ domain. Cytological studies using indirect immunofluorescence microscopy revealed that FIG is a peripheral protein that uses one of its coiled coil domains to localize to the Golgi apparatus. To ascertain the modalities of this Golgi localization, the same coiled coil region was tested for its ability to interact with a panel of coiled coil domain-containing integral membrane Golgi proteins. Using a series of GST fusion protein binding assays, co-immunofluorescence and co-immunoprecipitation experiments, we show that FIG specifically binds to the coiled coil domain-containing Q-SNARE (Q-soluble NSF attachment protein receptor) protein syntaxin 6 both in vitro and in vivo. The structural features of FIG and its interaction with a SNARE protein suggest that FIG may play a role in membrane vesicle trafficking. This is the first example of a PDZ domain-containing peripheral protein that localizes to the Golgi through a coiled coil-mediated interaction with a resident membrane protein. Our results broaden the scope of PDZ domain-mediated functions.
Charest
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Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. charest@mit.edu
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D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002460:Cell Line; D018076:DNA, Complementary; D019143:Evolution, Molecular; D005260:Female; D006056:Golgi Apparatus / Q000378:metabolism*; D000077614:Golgi Matrix Proteins; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016297:Mutagenesis, Site-Directed; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism; D009928:Organ Specificity; D010802:Phylogeny; D014176:Protein Biosynthesis; D011487:Protein Conformation; D050765:Qa-SNARE Proteins; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D050600:SNARE Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D014162:Transfection; D033921:Vesicular Transport Proteins
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018076:DNA, Complementary; C434484:GOPC protein, human; D000077614:Golgi Matrix Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D011993:Recombinant Fusion Proteins; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins; C033652:postsynaptic density proteins