EXPERIMENTAL and MOLECULAR MEDICINE, Vol. 44, No. 6, 363-368, June 2012 Dendroaspis natriuretic peptide regulates the cardiac L-type 2+ Ca channel activity by the phosphorylation of α1c proteins Seon-Ah Park1*, Tae-Geun Kim1*, Myung-Kwan Han2, Ki-Chan Ha1, Sung-Zoo Kim3 and Yong-Geun Kwak1,4* 1Department of Pharmacology 2Department of Microbiology 3Department of Physiology and Institute for Medical Science Chonbuk National University Medical School Jeonju 560-182, Korea 4Corresponding author: Tel, 82-63-270-3091; Fax, 82-63-275-2855; E-mail, ygkwak@jbnu.ac.kr *These authors contributed equally to this work. http://dx.doi.org/10.3858/emm.2012.44.6.041 Accepted 23 February 2012 Available Online 27 February 2012 Abbreviations: ANP, atrial natriuretic peptide; APD, action potential duration; BNP, brain natriuretic peptide; CNP, C-type natriuretic peptide; d-DNP, C-terminal-deleted DNP; DNP, dendroaspis natriuretic peptide; IC50, half maximal inhibitory concentration; ICa,L, L-type Ca2+ current; PKG, protein kinase G Abstract Dendroaspis natriuretic peptide (DNP), a new member of the natriuretic peptide family, is structurally similar to atrial, brain, and C-type natriuretic peptides. However, the effects of DNP on the cardiac function are poorly defined. In the present study, we examined the effect of DNP on the cardiac L-type Ca2+ channels in rab- bit ventricular myocytes. DNP inhibited the L-type Ca2+ current (ICa,L) in a concentration dependent manner with a IC50 of 25.5 nM, which was blocked by an inhibitor of protein kinase G (PKG), KT5823 (1 μM). DNP did not affect the voltage dependence of activation and in- activation of ICa,L. The α1c subunit of cardiac L-type Ca2+ channel proteins was phosphorylated by the treatment of DNP (1 μM), which was completely blocked by KT5823 (1 μM). Finally, DNP also caused the shortening of action potential duration in rabbit ventricular tissue by 22.3 ± 4.2% of the control (n = 6), which was com- pletely blocked by KT5823 (1 μM). These results clearly indicate that DNP inhibits the L-type Ca2+ channel activ- ity by phosphorylating the Ca2+ channel protein via PKG activation. Keywords: calcium channels, L-type; cyclic GMP-de- pendent protein kinases; dendroaspis natriuretic pep- tide; myocytes, cardiac; rabbits Introduction A new member of the natriuretic peptide family, dendroaspis natriuretic peptide (DNP), has been reported. DNP, originally isolated from the venom of the Dendroaspis angusticeps or green Mamba snake, is a peptide of 38 amino acids containing a 17 amino acid disulfide ring structure with a 15-residue C terminal extension (Schweitz et al., 1992). This peptide shares structural similarity to atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) of myocardial cell origin, and C-type natriuretic peptide (CNP) of endothelial cell origin (Schweitz et al., 1992). Reports indicate that DNP possesses biologic properties that are similar to the other natriuretic peptides (Schweitz et al., 1992; Lisy et al., 1999, 2001; Lee and Kim, 2002). Synthetic DNP potently relaxes rodent aorta and isolated canine coronary arteries with potencies comparable to that of ANP (Schweitz et al., 1992; Wennberg and Burnett, 1997; Collins et al., 2000). Furthermore, DNP displaces ANP binding from the natriuretic peptide receptors (Schweitz et al., 1992; Collins et al., 2000). Interestingly, it has been reported that DNP immunoreactivity is present in human plasma and atrial myocardium (Schirger et al., 1999; Lisy et al., 2001) and is elevated in the plasma of humans with congestive heart failure (CHF) (Schirger et al., 1999). More recently, Lisy et al. (2001) proposed that DNP has potential as a new intravenous agent for the treatment of decompensated CHF. Although synthetic DNP suggests its potential use in the cardiovascular disease states such as CHF, the effects of DNP on the cardiac function are poorly defined. The voltage- and time-dependent slow (L-type) Ca2+ channels in the cardiac myocytes play a pivotal role in regulating the cardiac function, and can be Copyright ⓒ 2012 by the Korean Society for Biochemistry and Molecular Biology This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.