title: Vesicular localization and characterization of a novel post-proline-cleaving aminodipeptidase, quiescent cell proline dipeptidase.
abstract: A large number of chemokines, cytokines, and signal peptides share a highly conserved X-Pro motif on the N-terminus. The cleavage of this N-terminal X-Pro dipeptide results in functional alterations of chemokines such as RANTES, stroma-derived factor-1, and macrophage-derived chemokine. Until recently, CD26/DPPIV was the only known protease with the ability to cleave N-terminal X-Pro motifs at neutral pH. We have isolated and cloned a novel serine protease, quiescent cell proline dipeptidase (QPP), with substrate specificity similar to that of CD26/DPPIV. In this paper we show that QPP, like CD26/DPPIV, is synthesized with a propeptide and undergoes N:-glycosylation. Interestingly, this glycosylation is required for QPP enzymatic activity, but not for its localization. Unlike the cell surface molecule, CD26/DPPIV, QPP is targeted to intracellular vesicles that are distinct from lysosomes. Proteinase K treatment of intact vesicles indicates that QPP is located within the vesicles. These vesicles appear to have a secretory component, as QPP is secreted in a functionally active form in response to calcium release. The presence of QPP in the vesicular compartment suggests that molecules bearing the N-terminal X-Pro motif can be cleaved at multiple sites within and outside the cell. These results expand the potential site(s) and scope of a process that appears to be an important mechanism of post-translational regulation.
authors.affiliation: Department of Pathology, Program in Immunology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA.
authors.forename: M
authors.initials: M
authors.lastname: Chiravuri
authors.forename: F
authors.initials: F
authors.lastname: Agarraberes
authors.forename: S L
authors.initials: SL
authors.lastname: Mathieu
authors.forename: H
authors.initials: H
authors.lastname: Lee
authors.forename: B T
authors.initials: BT
authors.lastname: Huber
mesh_terms: D000595:Amino Acid Sequence; D002236:Carbohydrate Conformation; D022162:Cytoplasmic Vesicles / Q000201:enzymology*; D004150:Dipeptidases / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*; D004789:Enzyme Activation; D006031:Glycosylation; D006801:Humans; D006868:Hydrolysis; D007399:Interphase; D007424:Intracellular Fluid / Q000201:enzymology; D019169:Jurkat Cells; D008247:Lysosomes / Q000201:enzymology; D008969:Molecular Sequence Data; D011392:Proline / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals; D012697:Serine Endopeptidases / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism
chemical_list: D021382:Protein Sorting Signals; D011392:Proline; D004150:Dipeptidases; C022449:proline dipeptidase; D012697:Serine Endopeptidases