Steady-state mRNA levels of G protein subunits in developing rabbit myocardium.
Cardiac responsiveness to beta-adrenergic stimulation changes with age. Developmental changes in expression of guanine nucleotide-binding coupling protein (G protein) subunits may account for these physiologic changes. We measured steady-state levels of mRNA encoding the alpha-subunit of the specific G protein that stimulates adenylyl cyclase (Gs alpha) and three isoforms of beta-subunit of G proteins (G beta) in developing myocardium. Total RNA prepared from the right and left ventricles of fetal, neonatal, juvenile, and adult rabbits was size-fractionated, blotted, and probed with 32P-labeled cDNAs encoding rat Gs alpha, bovine G beta-1, human G beta-2, and human G beta-3. For standardization, these blots were subsequently hybridized with a 32P-labeled cDNA encoding glyceraldehyde 3-phosphate dehydrogenase (GAPD). Two-dimensional densitometric analysis of autoradiographs was used to quantify relative hybridization intensities. An age-dependent decrease in mRNAs encoding Gs alpha, G beta-1, and G beta-2 relative to mRNA encoding GAPD was observed in both ventricles, while G beta-3 mRNA was not detected. At all ages studied, levels of Gs alpha and G beta-1 mRNA were similar in the two ventricles. However, G beta-2 mRNA declined more in the left ventricle than in the right ventricle during maturation. Our results demonstrate developmental control in heart for mRNAs encoding several G protein subunits. In addition, differential declines in G beta-1 and G beta-2 mRNA in the right ventricle suggest that these G beta isoforms are regulated uniquely and may reflect functional roles for these G beta isoforms in different signaling cascades.
Fattal
O
O
Department of Pediatrics, UCLA School of Medicine 90095, USA.
Van Dop
C
C
Chen
F
F
Chang
J T
JT
Zoltan
T B
TB
Wetzel
G T
GT
Klitzner
T S
TS
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D006321:Heart / Q000196:embryology*; D009206:Myocardium / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D011817:Rabbits; D011943:Receptors, Adrenergic, beta / Q000378:metabolism
D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases