Lack of proteolytic processing of alpha-L-fucosidase in human skin fibroblasts

• Published in: Journal of cellular physiology Vol. 137; no. 3; p. 411
• Main Authors: Leibold, D M, Robinson, C B, Scanlin, T F, Glick, M C
• Format: Journal Article
• Language: English
• Published: United States 01.12.1988
• Subjects: Acetylglucosaminidase - metabolism; alpha-L-Fucosidase - analysis; alpha-L-Fucosidase - biosynthesis; alpha-L-Fucosidase - metabolism; Cells, Cultured; Electrophoresis, Polyacrylamide Gel; Fibroblasts; Humans; Molecular Weight; Precipitin Tests; Protein Processing, Post-Translational; Tunicamycin - pharmacology
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041370304

Acid hydrolases are synthesized as precursors that undergo several posttranslational modifications including proteolytic processing to a smaller mature enzyme. The amount of proteolytic processing varies for different acid hydrolases, and many details of the intracellular pathways are not known. The processing of alpha-L-fucosidase was distinguished from that of other acid hydrolases reported when studied in systematic pulse-chase labeling experiments. Only one form of alpha-L-fucosidase, Mr 56,000-57,000, was demonstrated intra- and extracellularly. Under the same conditions, N-acetyl-beta-D-glucosaminidase was shown to be processed with several forms, as previously reported by Hasilik and Neufeld (1980a). To obtain these results, human skin fibroblasts were labeled metabolically with L-[3H]leucine for periods of 20 min to 8 hr with varying periods of chase from 1 to 96 hr with nonradioactive L-leucine. alpha-L-Fucosidase was immunoprecipitated by a polyclonal antibody from material extracted from cells and ammonium sulfate precipitated medium and was examined by polyacrylamide gel electrophoresis under denaturing conditions. N-Acetyl-beta-D-glucosaminidase was examined with similar procedures and served as a control for the methods. Tunicamycin treatment of the cells was used to show that glycosylation did not obscure proteolytic processing because, again, only one form of the intra- and extracellular enzyme was observed, although of smaller size, Mr 52,000-53,000. In addition, separation of the cells into prelysosomal and lysosomal fractions showed only one form of the enzyme. It is concluded that alpha-L-fucosidase does not undergo proteolytic processing in human skin fibroblasts in the usual manner described for other acid hydrolases.