Proprotein Convertases Process and Thereby Inactivate Formylglycine-generating Enzyme

• Published in: The Journal of biological chemistry 2013-02, Vol.288 (8), p.5828-5839
• Main Authors: Ennemann, Eva C., Radhakrishnan, Karthikeyan, Mariappan, Malaiyalam, Wachs, Michaela, Pringle, Thomas H., Schmidt, Bernhard, Dierks, Thomas
• Format: Article
• Language: English
• Subjects: Amino Acid Motifs; Animals; Arginine - chemistry; Binding Sites; Cell Biology; Cell Line, Tumor; CHO Cells; Cricetinae; Endoplasmic Reticulum (ER); Endoplasmic Reticulum - metabolism; Enzyme Inhibitors - pharmacology; Formylglycine-generating Enzyme; Furin; Furin - chemistry; Glycine - analogs & derivatives; Glycine - chemistry; HEK293 Cells; HeLa Cells; Homeostasis; Humans; Intracellular Processing; Oxidoreductases Acting on Sulfur Group Donors; Plasmids - metabolism; Post-translational Modification; Proprotein Convertases; Proprotein Convertases - metabolism; Protein Processing; Protein Processing, Post-Translational; Protein Secretion; Protein Structure, Tertiary; Proteolysis; Sulfatases; Sulfatases - antagonists & inhibitors; Tyrosine - chemistry
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.405159

Formylglycine-generating enzyme (FGE) post-translationally converts a specific cysteine in newly synthesized sulfatases to formylglycine (FGly). FGly is the key catalytic residue of the sulfatase family, comprising 17 nonredundant enzymes in human that play essential roles in development and homeostasis. FGE, a resident protein of the endoplasmic reticulum, is also secreted. A major fraction of secreted FGE is N-terminally truncated, lacking residues 34–72. Here we demonstrate that this truncated form is generated intracellularly by limited proteolysis mediated by proprotein convertase(s) (PCs) along the secretory pathway. The cleavage site is represented by the sequence RYSR72↓, a motif that is conserved in higher eukaryotic FGEs, implying important functionality. Residues Arg-69 and Arg-72 are critical because their mutation abolishes FGE processing. Furthermore, residues Tyr-70 and Ser-71 confer an unusual property to the cleavage motif such that endogenous as well as overexpressed FGE is only partially processed. FGE is cleaved by furin, PACE4, and PC5a. Processing is disabled in furin-deficient cells but fully restored upon transient furin expression, indicating that furin is the major protease cleaving FGE. Processing by endogenous furin occurs mostly intracellularly, although also extracellular processing is observed in HEK293 cells. Interestingly, the truncated form of secreted FGE no longer possesses FGly-generating activity, whereas the unprocessed form of secreted FGE is active. As always both forms are secreted, we postulate that furin-mediated processing of FGE during secretion is a physiological means of higher eukaryotic cells to regulate FGE activity upon exit from the endoplasmic reticulum. Background: The ER-resident formylglycine-generating enzyme (FGE), essential for post-translational activation of all eukaryotic sulfatase enzymes, is N-terminally processed during secretion. Results: Processing is mediated by furin at a conserved R/K-YS-R/K↓ cleavage site and leads to FGE inactivation. Conclusion: Processing serves to regulate the amount of FGE activity following ER exit. Significance: Processing is never complete, thus suggesting an extra-ER function of FGE.