Báo cáo khoa học: Cyclic ADP-ribose requires CD38 to regulate the release of ATP in visceral smooth

Cyclic ADP-ribose requires CD38 to regulate the release of

ATP in visceral smooth muscle

Leonie Durnin and Violeta N. Mutafova-Yambolieva

Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA

Keywords

ATP; bladder; cADP-ribose; CD38; NAD;

purinergic neurotransmission

Correspondence

V. N. Mutafova-Yambolieva, Department of

Physiology and Cell Biology, University

of Nevada School of Medicine, Center

for Molecular Medicine ⁄ MS 575, Reno,

NV 89557-0575, USA

Fax: +1 775 784 6903

Tel: +1 775 784 6274

E-mail: [email protected]

(Received 30 April 2011, revised 24 June

2011, accepted 30 June 2011)

doi:10.1111/j.1742-4658.2011.08233.x

It is well established that the intracellular second messenger cADP-ribose

(cADPR) activates Ca2+ release from the sarcoplasmic reticulum through

ryanodine receptors. CD38 is a multifunctional enzyme involved in the for￾mation of cADPR in mammals. CD38 has also been reported to transport

cADPR in several cell lines. Here, we demonstrate a role for extracellular

cADPR and CD38 in modulating the spontaneous, but not the electrical

field stimulation-evoked, release of ATP in visceral smooth muscle. Using a

small-volume superfusion assay and an HPLC technique with fluorescence

detection, we measured the spontaneous and evoked release of ATP in

bladder detrusor smooth muscles isolated from CD38+ ⁄ + and CD38) ⁄ )

mice. cADPR (1 nM) enhanced the spontaneous overflow of ATP in blad￾ders isolated from CD38+ ⁄ + mice. This effect was abolished by the inhibi￾tor of cADPR receptors on sarcoplasmic reticulum 8-bromo-cADPR

(80 lM) and by ryanodine (50 lM), but not by the nonselective P2 puriner￾gic receptor antagonist pyridoxal phosphate 6-azophenyl-2¢,4¢-disulfonate

(30 lM). cADPR failed to facilitate the spontaneous ATP overflow in

bladders isolated from CD38) ⁄ ) mice, indicating that CD38 is crucial for

the enhancing effects of extracellular cADPR on spontaneous ATP release.

Contractile responses to ATP were potentiated by cADPR, suggesting that

the two adenine nucleotides may work in synergy to maintain the resting

tone of the bladder. In conclusion, extracellular cADPR enhances the

spontaneous release of ATP in the bladder by influx via CD38 and subse￾quent activation of intracellular cADPR receptors, probably causing an

increase in intracellular Ca2+ in neuronal cells.

Introduction

Cyclic ADP-ribose (cADPR) is an intracellular second

messenger that can release Ca2+ from ryanodine-sensi￾tive stores [1] in a wide variety of cells [2], including

cells in the nervous system [3]. In mammals, cADPR is

generated from NAD by ADP-ribosyl cyclase associ￾ated with CD38, a multifunctional type II integral

membrane glycoprotein with ADP-ribosyl cyclase and

NAD-glycohydrolase activities [2,4,5]. The catalytic

site of CD38 faces the ectocellular space [6,7], making

this enzyme suitable as a regulator of extracellular b￾NAD+ and cADPR levels [8]. Therefore, cADPR

could be produced extracellularly in each system that

releases b-NAD+ and expresses membrane-bound

CD38. In 3T3 murine fibroblasts and HeLa cells,

CD38 also mediates intracellular influx of cADPR

[9,10]. Furthermore, extracellular cADPR can stimu￾late NG108-15 cells, a neurally derived clonal cell line,

and elevate intracellular Ca2+ levels [11]. It is presently

Abbreviations

ADPR, ADP-ribose; BoNTA, botulinum neurotoxin A; cADPR, cADP-ribose; CBX, carbenoxolone; cGDPR, cGDP-ribose; eADPR, 1,N 6

-etheno￾ADPR; EFS, electrical field stimulation; FFA, flufenamic acid; NGD, nicotinamide guanine dinucleotide; PPADS, pyridoxal phosphate

6-azophenyl-2¢,4¢-disulfonate; PS, prestimuation; SE, standard error; TTX, tetrodotoxin.

FEBS Journal 278 (2011) 3095–3108 ª 2011 The Authors Journal compilation ª 2011 FEBS 3095