title: Molecular characterization of a novel cell surface ADP-ribosyl cyclase from the sea urchin.
abstract: The sea urchin is an extensively used model system for the study of calcium signalling by the messenger molecules NAADP and cyclic ADP-ribose. Both are synthesized by ADP-ribosyl cyclases but our molecular understanding of these enzymes in the sea urchin is limited. We have recently reported the cloning of an extended family of sea urchin ADP-ribosyl cyclases and shown that one of these enzymes (SpARC1) is active within the endoplasmic reticulum lumen. These studies suggest that production of messengers is compartmentalized. Here we characterize the properties of SpARC2. SpARC2 catalyzed both NAADP and cyclic ADP-ribose production. Unusually, the NAD surrogate, NGD was a poor substrate. In contrast to SpARC1, heterologously expressed SpARC2 localized to the plasma membrane via a glycosylphosphatidylinositol (GPI)-anchor. Transcripts for SpARC2 were readily detectable in sea urchin eggs and a majority of the endogenous membrane bound activity was found to be GPI-anchored. Our data reveal striking differences in the properties of sea urchin ADP-ribosyl cyclases and provide further evidence that messenger production may occur outside of the cytosol.
authors.affiliation: Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK.
authors.forename: Dev
authors.initials: D
authors.lastname: Churamani
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Boulware
authors.forename: Latha
authors.initials: L
authors.lastname: Ramakrishnan
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Geach
authors.forename: Andrew C R
authors.initials: AC
authors.lastname: Martin
authors.forename: Victor D
authors.initials: VD
authors.lastname: Vacquier
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Marchant
authors.forename: Leslie
authors.initials: L
authors.lastname: Dale
authors.forename: Sandip
authors.initials: S
authors.lastname: Patel
mesh_terms: D036541:ADP-ribosyl Cyclase / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D036563:Cyclic ADP-Ribose / Q000096:biosynthesis; D006801:Humans; D008856:Microscopy, Fluorescence; D009249:NADP / Q000031:analogs & derivatives / Q000096:biosynthesis; D009865:Oocytes / Q000201:enzymology; D012617:Sea Urchins / Q000201:enzymology*; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D036563:Cyclic ADP-Ribose; D009249:NADP; C024376:NAADP; D010738:Type C Phospholipases; D036541:ADP-ribosyl Cyclase