New therapeutic targets of heart failure in regulatory pathways of excitation-contraction coupling. Excitation-contraction coupling and its regulation by Gs-activating G protein–coupling receptor (GPCR) and A-kinase signaling. A series of genes have been subjected to target validation analysis via transgenic and somatic gene transfer studies with a variety of viral vector systems and protocols. 1. β2-adrenergic receptor (β2AR). β2AR transgenic (β2AR-TG) mice display a hypertrophic cardiomyopathy phenotype and do not rescue the phenotype of failing muscle-specific LIM-only protein knockout (MLPKO) mice. β2AR-TG mice fail to rescue the HCM phenotype of R403QαMHC-TG mice. Percutaneous or intramuscular Adeno/β2AR delivery results in enhanced contractility in normal rabbit or cardiomyopathic hamsters. 2. βARK inhibitor (βARKct). βARKct-TG mice partially rescue cardiomyopathic phenotypes of MLPKO mice and R403QαMHC-TG mice. Adeno/βARKct improves contractility and delays heart failure development in post–myocardial infarction rabbits. 3. Adenylyl cyclase type VI (AC-typeVI). AC-typeVI–TG mice rescue heart failure in G_q-TG mice. Percutaneous Adeno/AC-typeVI delivery enhances cardiac contractility in normal pigs. 4. Phosphodiesterase. Several human clinical trials have confirmed that phosphodiesterase’s pharmacological inhibition improves cardiac function, although at the risk of decreased long-term survival; current clinical use is primarily confined to end-stage heart failure awaiting transplantation. 5. SERCA2: SERCA2-TG mice are hyperkinetic, whereas heterozygous null animals are hypokinetic. Adeno/SERCA2 gene delivery improves cardiac contractility and prognosis of postaortic banded rats. SERCA1: SERCA1-TG mice are hyperkinetic. Adeno/SERCA1 has been used to support intramuscular delivery of Kv2.1 in normal guinea pig hearts. 6. Phospholamban (PLN). PLN-TG mice are hypokinetic, whereas knockout mice are hyperkinetic. Adeno and AAV/mutant PLN suppress cardiomyopathic hamster heart failure development. 7. FKBP12.6: In vitro Adeno/FKBP12.6–transfected cardiomyocyte increases contractility. Parvalbumin: Adeno/parvalbumin intramuscular delivery enhances normal rat cardiac relaxation. GRK, GPCR kinase; I_Ca,L, L-type calcium channel (dihydropyridine receptor); RyR, ryanodine receptor; JP-2, junctophilin-2. See supplemental reading list (www.jci.org/cgi/content/full/109/7/849/DC1) for detailed references.