Abstract
ARTC2.2 is a toxin-related, GPI-anchored ADP-ribosyltransferase expressed by murine T cells. In response to NAD(+) released from damaged cells during inflammation, ARTC2.2 ADP-ribosylates and thereby gates the P2X7 ion channel. This induces ectodomain shedding of metalloprotease-sensitive cell surface proteins. In this study, we show that ARTC2.2 itself is a target for P2X7-triggered ectodomain shedding. We identify the metalloprotease cleavage site 3 aa upstream of the predicted GPI anchor attachment site of ARTC2.2. Intravenous injection of NAD(+) increased the level of enzymatically active ARTC2.2 in serum, indicating that this mechanism is operative also under inflammatory conditions in vivo. Radio-ADP-ribosylation assays reveal that shedding refocuses the target specificity of ARTC2.2 from membrane proteins to secretory proteins. Our results uncover nucleotide-induced membrane-proximal proteolysis as a regulatory mechanism to control the substrate specificity of ARTC2.2.
Copyright © 2015 by The American Association of Immunologists, Inc.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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ADAM Proteins / metabolism
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ADAM17 Protein
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ADP Ribose Transferases / blood
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ADP Ribose Transferases / genetics
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ADP Ribose Transferases / metabolism*
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Adenosine Diphosphate Ribose / metabolism
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Animals
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Cell Line, Tumor
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Cell Membrane / drug effects
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Cell Membrane / metabolism
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Flow Cytometry
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Glycosylphosphatidylinositols / metabolism
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HEK293 Cells
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Humans
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L-Selectin / genetics
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L-Selectin / metabolism
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Membrane Proteins / genetics
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Membrane Proteins / metabolism*
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Mice, Inbred C57BL
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Mice, Knockout
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Mice, Transgenic
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NAD / metabolism*
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NAD / pharmacology
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Proteolysis / drug effects
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Receptors, Purinergic P2X7 / genetics
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Receptors, Purinergic P2X7 / metabolism
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Substrate Specificity
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T-Lymphocyte Subsets / enzymology
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T-Lymphocyte Subsets / metabolism
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T-Lymphocytes / enzymology*
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T-Lymphocytes / metabolism
Substances
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Glycosylphosphatidylinositols
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Membrane Proteins
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Receptors, Purinergic P2X7
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NAD
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L-Selectin
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Adenosine Diphosphate Ribose
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ADP Ribose Transferases
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ARTC2.2 protein, mouse
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Art2b protein, mouse
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ADAM Proteins
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ADAM17 Protein