Referenced in: none

Automatically associated channels: HCN3

Title: A novel mechanism for coupling cellular intermediary metabolism to cytosolic Ca2+ signaling via CD38/ADP-ribosyl cyclase, a putative intracellular NAD+ sensor.

Authors: Li Sun, Olugbenga A Adebanjo, Anatoliy Koval, Hindupur K Anandatheerthavarada, Jameel Iqbal, Xing Y Wu, Baljit S Moonga, Xue B Wu, Gopa Biswas, Peter J R Bevis, Masoyoshi Kumegawa, Solomon Epstein, Christopher L-H Huang, Narayan G Avadhani, Etsuko Abe, Mone Zaidi

Journal, date & volume: FASEB J., 2002 Mar , 16, 302-14

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/11874980

Abstract
CD38 is an ectocyclase that converts NAD+ to the Ca2+-releasing second messenger cyclic ADP-ribose (cADPr). Here we report that in addition to CD38 ecto-catalysis, intracellularly expressed CD38 may catalyze NAD+-->cADPr conversion to cause cytosolic Ca2+ release. High levels of CD38 were found in the plasma membranes, endoplasmic reticulum, and nuclear membranes of osteoblastic MC3T3-E1 cells. More important, intracellular CD38 was colocalized with target ryanodine receptors. The cyclase also converted a NAD+ surrogate, NGD+, to its fluorescent product, cGDPr (Km approximately 5.13 microM). NAD+ also triggered a cytosolic Ca2+ signal. Similar results were obtained with NIH3T3 cells, which overexpressed a CD38-EGFP fusion protein. The Delta(-49)-CD38-EGFP mutant with a deleted amino-terminal tail and transmembrane domain appeared mainly in the mitochondria with an expected loss of its membrane localization, but the NAD+-induced cytosolic Ca2+ signal was preserved. Likewise, Ca2+ release persisted in cells transfected with the Myr-Delta(-49)-CD38-EGFP or Delta(-49)-CD38-EGFP-Fan mutants, both directed to the plasma membrane but in an opposite topology to the full-length CD38-EGFP. Finally, ryanodine inhibited Ca2+ signaling, indicating the downstream activation of ryanodine receptors by cADPr. We conclude that intracellularly expressed CD38 might link cellular NAD+ production to cytosolic Ca2+ signaling.