Molecular cloning, expression, and functional characterization of a novel member of the CD38 family of ADP-ribosyl cyclases

We report the molecular cloning and functional characterization of a novel member of the CD38 family of cyclic ADP-ribose (cADPr)-generating cyclases. We cloned a cDNA insert that encoded a 298-amino-acid-long protein (M-w si milar to 39 kDa). The predicted protein displayed 69, 61, and 58% similarit y, respectively, to mouse, rat, and human CD38, Rabbit CD38 was also 28% ho mologous to Aplysia ADP-ribosyl cyclase and leukocyte CD157 (another ADP-ri bosyl cyclase); the three cyclases shared 10 cysteine and 2 adjacent prolin e residues, We then transfected CD38-negative NIH3T3 cells with cDNA encodi ng a CD38-EGFP fusion protein. Epifluorescence microscopy showed intense EG FP fluorescence confirming CD38 expression. We finally confirmed the ADP-ri bosyl cyclase activity of the expressed CD38 by measuring its ability to ca talyze the cyclization of the nicotinamide adenine dinucleotide (NAD(+)) su rrogate, NGD(+), to its fluorescent nonhydrolyzable derivative, cGDPr. (C) 2000 Academic Press.