Molecular characterization of a novel cell surface ADP-ribosyl cyclase from the sea urchin.
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.
Churamani
Dev
D
Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK.
Boulware
Michael J
MJ
Ramakrishnan
Latha
L
Geach
Timothy J
TJ
Martin
Andrew C R
AC
Vacquier
Victor D
VD
Marchant
Jonathan S
JS
Dale
Leslie
L
Patel
Sandip
S
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
D036563:Cyclic ADP-Ribose; D009249:NADP; C024376:NAADP; D010738:Type C Phospholipases; D036541:ADP-ribosyl Cyclase