MOLECULAR CHARACTERIZATION OF GOLGIN-245, A NOVEL GOLGI-COMPLEX PROTEIN CONTAINING A GRANIN SIGNATURE

The serum from a Sjogren's syndrome patient with anti-Golgi antibodies was used as a probe to isolate a 4.6-kilobase pair cDNA insert from a HeLa cDNA library. Expression of the cDNA in Escherichia coil and the in vitro translation products of the cDNA yielded a recombinant prote in that migrated in SDS-polyacrylamide gel electrophoresis at 180 kDa. This protein was immuno-precipitated by the human anti-Gels serum and by immune rabbit serum but not by normal human serum or preimmune rab bit serum. Western blot analysis showed that the prototype human and i mmune rabbit sera recognized a 245-kDa protein, suggesting that the is olated clone contained a partial cDNA. The 5'-upstream sequence obtain ed by the rapid amplification of cDNA ends methodology using human pla cental cDNA and the combined HeLa cDNA contained 6965 base pairs and e ncoded a protein of 245 kDa and, like other Golgi autoantigens describ ed earlier, is highly rich in coiled-coils. The deduced amino acid seq uence included the decapeptide ESLALEELEL, which was identified as one of two signature sequences previously reported in a family of peptide hormones and neuropeptides known as ''granins.'' This is the first re port of a Golgi complex autoantigen that bears structural similarities to the granin family of proteins.