Processing and Secretion of Lysosomal Acid α-Glucosidase In Tetrahymena Wild Type and Secretion-Deficient Mutant Cells |
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Authors: | YOSHIKO BANNO YUKIO OKANO KIYOSHI FURUKAWA ARNO TIEDTKE AKIRA KOBATA YOSHINORI NOZAWA |
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Institution: | Department of Biochemistry, Gifu University School of Medicine, Tsukasamachi 40, Gifu 500.;Department of Biochemistry, the Institute of Medical Science, the University of Tokyo, Minato-ku, Tokyo 108, Japan;Institut für Allgemeine Zoologie and Genetik, University of Münster, Schlossplatz 5, D- W-4400 Münster, Germany |
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Abstract: | ABSTRACT. The proteolytic processing and secretion of a lysosomal enzyme, acid α-glucosidase, was studied by pulse-chase labeling with 35S]methionine in Tetrahymena thermophila CU-399 cells treated with ammonium chloride. This cell secreted a large amount of acid α-glucosidase into the cultured medium during starvation. the secretion was found to be repressed by addition of ammonium chloride (NH4Cl). Acid α-glucosidase was produced as a precursor form (108 kDa) and then processed to a mature polypeptide (105 kDa) within 60 min. This mature enzyme was secreted into the media within 2-3 h after chase, whereas the precursor form was not secreted by either control cells or NH4Cl-treated cells. NH4Cl did not affect the processing of the precursor acid α-glucosidase. Processing profile of this enzyme was apparently indistinguishable from that of the mutant MS-1 defective in lysosomal enzyme secretion. Furthermore, the purified extracellular (CU-399) and intracellular (MS-1) acid a-glucosidases were the same in molecular mass (105 kDa) and enzymatic properties. They contained no mannose 6-phosphate residues in N-linked oligosaccharides. These results suggested that unlike mammalian cells, Tetrahymena acid α-glucosidase may be transferred to lysosomes by a mannose 6-phosphate receptor-independent mechanism, and also that low pH was not essential for the proteolytic processing of precursor polypeptide. |
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Keywords: | Acid α-glucosidase effect of ammonium chloride processing secretion Tetrahymena |
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