Molecular characterization of a novel intracellular ADP-ribosyl cyclase.
BACKGROUND
ADP-ribosyl cyclases are remarkable enzymes capable of catalyzing multiple reactions including the synthesis of the novel and potent intracellular calcium mobilizing messengers, cyclic ADP-ribose and NAADP. Not all ADP-ribosyl cyclases however have been characterized at the molecular level. Moreover, those that have are located predominately at the outer cell surface and thus away from their cytosolic substrates.


RESULTS
Here we report the molecular cloning of a novel expanded family of ADP-ribosyl cyclases from the sea urchin, an extensively used model organism for the study of inositol trisphosphate-independent calcium mobilization. We provide evidence that one of the isoforms (SpARC1) is a soluble protein that is targeted exclusively to the endoplasmic reticulum lumen when heterologously expressed. Catalytic activity of the recombinant protein was readily demonstrable in crude cell homogenates, even under conditions where luminal continuity was maintained.


CONCLUSIONS
Our data reveal a new intracellular location for ADP-ribosyl cyclases and suggest that production of calcium mobilizing messengers may be compartmentalized.
Churamani
Dev
D
Department of Physiology, University College London, London, United Kingdom.
Boulware
Michael J
MJ
Geach
Timothy J
TJ
Martin
Andrew C R
AC
Moy
Gary W
GW
Su
Yi-Hsien
YH
Vacquier
Victor D
VD
Marchant
Jonathan S
JS
Dale
Leslie
L
Patel
Sandip
S
D036541:ADP-ribosyl Cyclase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D020013:Calcium Signaling; D003001:Cloning, Molecular; D036563:Cyclic ADP-Ribose / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000201:enzymology / Q000378:metabolism; D008969:Molecular Sequence Data; D009249:NADP / Q000031:analogs & derivatives / Q000378:metabolism; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012617:Sea Urchins / Q000201:enzymology; D016415:Sequence Alignment
D020033:Protein Isoforms; D036563:Cyclic ADP-Ribose; D009249:NADP; C024376:NAADP; D036541:ADP-ribosyl Cyclase