Gene transfer of heterologous G protein-coupled receptors to cardiomyocytes: differential effects on contractility.
In heart failure, reduced cardiac contractility is accompanied by blunted cAMP responses to beta-adrenergic stimulation. Parathyroid hormone (PTH)-related peptide and arginine vasopressin are released from the myocardium in response to increased wall stress but do not stimulate contractility or adenylyl cyclase at physiological concentrations. To bypass the defective beta-adrenergic signaling cascade, recombinant P1 PTH/PTH-related peptide receptors (rPTH1-Rs) and V(2) vasopressin receptors (rV(2)-Rs), which are normally not expressed in the myocardium and which are both strongly coupled to adenylyl cyclase, and recombinant beta(2)-adrenergic receptors (rbeta(2)-ARs) were overexpressed in cardiomyocytes by viral gene transfer. The capacity of endogenous hormones to increase contractility via the heterologous, recombinant receptors was compared. Whereas V(2)-Rs are uniquely coupled to Gs, PTH1-Rs and beta(2)-ARs are also coupled to other G proteins. Gene transfer of rPTH1-Rs or rbeta(2)-ARs to adult cardiomyocytes resulted in maximally increased basal contractility, which could not be further stimulated by adding receptor agonists. Agonists at rPTH1-Rs induced increased cAMP formation and phospholipase C activity. In contrast, healthy or failing rV(2)-R-expressing cardiomyocytes showed unaltered basal contractility. Their contractility and cAMP formation increased only at agonist exposure, which did not activate phospholipase C. In summary, we found that gene transfer of PTH1-Rs to cardiomyocytes results in constitutive activity of the transgene, as does that of beta(2)-ARS: In the absence of receptor agonists, rPTH1-Rs and rbeta(2)-ARs increase basal contractility, coupling to 2 G proteins simultaneously. In contrast, rV(2)-Rs are uniquely coupled to Gs and are not constitutively active, retaining their property to be activated exclusively on agonist stimulation. Therefore, gene transfer of V(2)-Rs might be more suited to test the effects of cAMP-stimulating receptors in heart failure than that of PTH1-Rs or beta(2)-ARS:
Laugwitz
K L
KL
Medizinische Klinik and Deutsches Herzzentrum München Institut für Experimentelle Onkologie und Therapieforschung, Technische Universität, Munich, Germany.
Weig
H J
HJ
Moretti
A
A
Hoffmann
E
E
Ueblacker
P
P
Pragst
I
I
Rosport
K
K
Schömig
A
A
Ungerer
M
M
D000256:Adenoviridae / Q000235:genetics; D037361:Adenylate Cyclase Toxin; D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism; D017077:Culture Media, Conditioned / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D003894:Deamino Arginine Vasopressin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D019204:GTP-Binding Proteins / Q000378:metabolism*; D018014:Gene Transfer Techniques; D005822:Genetic Vectors / Q000235:genetics / Q000494:pharmacology; D049452:Green Fluorescent Proteins; D006333:Heart Failure / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics; D009200:Myocardial Contraction / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000494:pharmacology; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism; D011817:Rabbits; D011869:Radioligand Assay; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D018016:Receptors, Parathyroid Hormone / Q000235:genetics / Q000378:metabolism*; D017483:Receptors, Vasopressin / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D019076:Transgenes / Q000235:genetics; D010738:Type C Phospholipases / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D017077:Culture Media, Conditioned; D008164:Luminescent Proteins; D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments; D011506:Proteins; D011956:Receptors, Cell Surface; D018016:Receptors, Parathyroid Hormone; D017483:Receptors, Vasopressin; D011993:Recombinant Fusion Proteins; D010566:Virulence Factors, Bordetella; D001127:Arginine Vasopressin; D049452:Green Fluorescent Proteins; D000242:Cyclic AMP; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D003894:Deamino Arginine Vasopressin