Evidence for selective coupling of alpha 1-adrenergic receptors to phospholipase C-beta 1 in rat neonatal cardiomyocytes.
Activation of phospholipase C (PLC) in neonatal rat cardiomyocytes (NCM) generates primarily inositol 1,4,5-trisphosphate (Ins(1,4,5)P(3)) in response to rises in intracellular Ca(2+), or inositol 1,4-bisphosphate (Ins(1,4)P(2)) in response to norepinephrine (NE) (Matkovich, S. J. and Woodcock, E. A. (2000) J. Biol. Chem. 275, 10845-10850). To examine the PLC subtype mediating the alpha(1)-adrenergic receptor response, PLC-beta(1) and PLC-beta(3) were overexpressed in NCM using adenoviral infection (Ad-PLC-beta(1) NCM and Ad-PLC-beta(3) NCM, respectively) and PLC responses assessed from [(3)H]inositol phosphate (InsP) generation in the presence of 10 mm LiCl. The [(3)H]InsP response to NE (100 microm) was enhanced in Ad-PLC-beta(1) NCM relative to cells infected with blank virus (Ad-MX NCM), but was reduced in Ad-PLC-beta(3) NCM. In contrast, the [(3)H]InsP response to ATP (100 microm) was not elevated in Ad-PLC-beta(1) NCM, and was enhanced rather than diminished in Ad-PLC-beta(3) NCM, showing that effects of the two PLC-beta isoforms were specific for particular receptor types. PLC-delta(1) overexpression selectively reduced NE-induced [(3)H]InsP responses, without affecting the ATP stimulation. The reduced NE response was associated with a selective loss of PLC-beta(1) expression in Ad-PLC-delta(1) NCM. alpha(1)-Adrenergic receptor activation caused phosphorylation of PLC-beta(1) but not PLC-beta(3), whereas stimulation by ATP induced phosphorylation of PLC-beta(3) but not PLC-beta(1.) Taken together, these studies provide evidence that NE-stimulated InsP generation in NCM is primarily mediated by PLC-beta(1), despite the presence of both PLC-beta(1) and PLC-beta(3) isoforms.
Arthur
J F
JF
Cellular Biochemistry Laboratory, Baker Medical Research Institute, Melbourne 8008, Victoria, Australia.
Matkovich
S J
SJ
Mitchell
C J
CJ
Biden
T J
TJ
Woodcock
E A
EA
D000818:Animals; D000831:Animals, Newborn; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D007295:Inositol Phosphates / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D054799:Phospholipase C beta; D054803:Phospholipase C delta; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D058473:Receptors, Purinergic P2Y2; D010738:Type C Phospholipases / Q000378:metabolism*
D007295:Inositol Phosphates; D007527:Isoenzymes; C546387:P2ry2 protein, rat; D018340:Receptors, Adrenergic, alpha-1; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; D010738:Type C Phospholipases; D054799:Phospholipase C beta; D054803:Phospholipase C delta; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins