tyrosine-o-sulfate and Pheochromocytoma

A secreted form of the amyloid beta protein precursor was isolated from the growth conditioned medium of the PC12 sympathetic nerve-like cell line. This protein is recognized by an antiserum that detects a protein of 140 kDa and a less abundant species of 115 kDa on NaDodSO4/acrylamide gels. The amyloid precursor proteins contain O-linked sugars and tyrosine sulfate and bind to the glycosaminoglycan heparin. These results suggest a role for extracellular sulfated glycoproteins in the pathogenesis of Alzheimer disease.

Topics: Adrenal Gland Neoplasms; Alzheimer Disease; Amyloid; Amyloid beta-Protein Precursor; Animals; Blotting, Western; Carbohydrates; Electrophoresis, Polyacrylamide Gel; Heparin; Immunoassay; Molecular Weight; Peptide Fragments; Pheochromocytoma; Protease Inhibitors; Protein Precursors; Rats; Tumor Cells, Cultured; Tyrosine

The O-sulfation of specific proteins on tyrosine residues was studied using the rat pheochromocytoma cell line PC12 as a model system. In intact PC12 cells labeled with inorganic [35S]sulfate, the major protein substrates for sulfation on tyrosine were four acidic polypeptides with apparent molecular weights of 113,000, 105,000, 86,000, and 84,000 designated as p113, p105, p86, and p84. After labeling of intact PC12 cells with inorganic [32P]phosphate, these four proteins were also found to be phosphorylated at serine residues. Peptide mapping after limited proteolysis indicated sequence homologies between p113 and p105, and between p86 and p84. In lysed PC12 cells, p113, p105, p86, and p84 were phosphorylated at serine residues by an endogenous protein kinase using [32P] ATP. Moreover, in the cell-free preparation, an enzymatic activity was detected that was able to catalyze the sulfation of the four proteins on tyrosine residues. This sulfation reaction, which used adenosine 3'-phosphate 5'-phospho[35S]sulfate as the sulfate donor, occurred in a particulate fraction of PC12 cells and was inhibited by 5 mM EDTA. These results demonstrate the presence in PC12 cells of a novel enzyme, designated here as a tyrosylprotein sulfotransferase, and imply a role for this enzyme in the post-translational processing of specific PC12 cell proteins.

Topics: Adrenal Gland Neoplasms; Animals; Molecular Weight; Neoplasm Proteins; Pheochromocytoma; Phosphorylation; Protein Processing, Post-Translational; Rats; Sulfotransferases; Sulfurtransferases; Tyrosine