Neuronal nitric oxide synthase signaling in the heart is regulated by the sarcolemmal calcium pump 4b.
BACKGROUND
Neuronal nitric oxide synthase (nNOS) has recently been shown to be a major regulator of cardiac contractility. In a cellular system, we have previously shown that nNOS is regulated by the isoform 4b of plasma membrane calcium/calmodulin-dependent ATPase (PMCA4b) through direct interaction mediated by a PDZ domain (PSD 95, Drosophilia Discs large protein and Zona occludens-1) on nNOS and a cognate ligand on PMCA4b. It remains unknown, however, whether this interaction has physiological relevance in the heart in vivo.


RESULTS
We generated 2 strains of transgenic mice overexpressing either human PMCA4b or PMCA ct120 in the heart. PMCA ct120 is a highly active mutant form of the pump that does not interact with or modulate nNOS function. Calcium was extruded normally from PMCA4b-overexpressing cardiomyocytes, but in vivo, overexpression of PMCA4b reduced the beta-adrenergic contractile response. This attenuated response was not observed in ct120 transgenic mice. Treatment with a specific nNOS inhibitor (N omega-propyl-L-arginine) reduced the beta-adrenergic response in wild-type and ct120 transgenic mice to levels comparable to those of PMCA4b transgenic animals. No differences in lusitropic response were observed in either transgenic strain compared with wild-type littermates.


CONCLUSIONS
These data demonstrate the physiological relevance of the interaction between PMCA4b and nNOS and suggests its signaling role in the heart.
Oceandy
Delvac
D
Division of Cardiovascular and Endocrine Sciences, University of Manchester, Oxford Rd, Manchester M13 9PT, United Kingdom.
Cartwright
Elizabeth J
EJ
Emerson
Michael
M
Prehar
Sukhpal
S
Baudoin
Florence M
FM
Zi
Min
M
Alatwi
Nasser
N
Venetucci
Luigi
L
Schuh
Kai
K
Williams
Judith C
JC
Armesilla
Angel L
AL
Neyses
Ludwig
L
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D006321:Heart / Q000502:physiology*; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000201:enzymology; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism*; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000235:genetics* / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism; D012508:Sarcolemma / Q000201:enzymology; D015398:Signal Transduction / Q000502:physiology*
D000318:Adrenergic beta-Agonists; D020746:Calcium Channels, L-Type; D011943:Receptors, Adrenergic, beta; D052248:Nitric Oxide Synthase Type I; C507517:ATP2B4 protein, human; D053499:Plasma Membrane Calcium-Transporting ATPases; D002118:Calcium