Glycosylation Directs Targeting and Activation of Cystatin F from Intracellular and Extracellular Sources

Jeff D. Colbert, Anna Plechanovova, Colin Watts

    Research output: Contribution to journalArticle

    33 Citations (Scopus)

    Abstract

    Cystatin F is a cysteine protease inhibitor that is selectively expressed in immune cells and unlike other cystatin family members is targeted to a significant extent to intracellular compartments. Initially made as an inactive glycosylated disulfide-linked dimer, cystatin F is converted to an active monomer by proteolytic cleavage following transport to the endosomal/lysosomal system. This active form of cystatin F targets cathepsin C/DPPI and probably other cathepsins in immune cells. We show that efficient targeting of cystatin F to the endocytic pathway is dependent not on its unique dimeric conformation but rather on its oligosaccharide chains. We demonstrate the unusual addition of N-linked sugars to an Asn-X-Cys motif in cystatin F and provide evidence that the mannose 6-phosphate sorting machinery is used to divert cystatin F from the secretory pathway and to mediate its uptake from extracellular pools. These studies identify a function for the oligosaccharides on cystatin F and raise the possibility that cystatin F might regulate proteases in trans by secretion in an inactive form by one cell and subsequent internalization and activation by another cell.

    Original languageEnglish
    Pages (from-to)425-437
    Number of pages13
    JournalTraffic
    Volume10
    Issue number4
    DOIs
    Publication statusPublished - Apr 2009

    Keywords

    • cathepsin C
    • cystatin
    • endocytosis
    • internalization
    • glycosylation
    • mannose 6-phosphate
    • DIPEPTIDYL PEPTIDASE-I
    • MANNOSE 6-PHOSPHATE RECEPTOR
    • RAY CRYSTAL-STRUCTURE
    • CYSTEINE PROTEINASES
    • N-ACETYLGLUCOSAMINIDASE
    • HEMATOPOIETIC-CELLS
    • LYSOSOMAL-ENZYMES
    • CATHEPSIN-S
    • GAMMA-TRACE
    • ENDOCYTOSIS

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