Differential Expression of CD38 and Two‐Pore Channels in Rat Arterial Smooth Muscles

Abstract

CD38 is a multifunctional enzyme responsible for the synthesis of cyclic adenosine diphosphated-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP). cADPR and NAADP trigger Ca2+ release via ryanodine receptors of sarcoplasmic reticulum, and NAADP receptors of lysosomal stores, respectively, and are thought to play important roles in vascular functions. Recent studies suggested that two-pore channels (TPC1 and TPC2) are NAADP receptors located in the endo-/lysosomes. However, there is little information on the expression of CD38 and TPC channels in different vascular tissues. Here we used western blot analysis and quantitative real-time PCR to examine the expression of CD38, TPC1 and TPC2 in aorta (AA), pulmonary (PA), mesenteric (MA), renal (RA), femoral (FA), tail (TA), and cerebral artery (CA) of rat. CD38 protein was clearly detected in CA, RA and PA. However, the signal was significantly less in AA, and was undetectable in FA and TA. In contrast, TPC1 and TPC2 mRNA were detected in all arteries, with TPC1 mRNA level five to ten-fold higher than that of TPC2. Furthermore, TPC1 mRNA level was significantly higher in CA, comparing to other arteries. Our results, hence, show that CD38, TPC1, and TPC2 channels are differentially expressed in various arteries; the differences in their expression may contribute to the diversity in vascular reactivity.