Interactions of multiple signaling pathways in neuropeptide Y-mediated bimodal vascular smooth muscle cell growth.
Neuropeptide Y (NPY), a sympathetic cotransmitter, acts via G protein-coupled receptors to stimulate constriction and vascular smooth muscle cell (VSMC) proliferation through interactions with its Y1 receptors. However, VSMC proliferation appears bimodal, with high- and low-affinity peaks differentially blocked by antagonists of both Y1 and Y5 receptors. Here, we sought to determine the signaling mechanisms of NPY-mediated bimodal mitogenesis. In rat aortic VSMCs, NPY's mitogenic effect at all concentrations was blocked by pertussis toxin and was associated with decreased forskolin-stimulated cAMP levels. NPY also increased intracellular calcium levels; in contrast to mitogenesis, this effect was dose dependent. The rise in intracellular Ca2+ depended on extracellular Ca2+ and was mediated via activation of Y1 receptors, but not Y5 receptors. Despite differences in calcium, the signaling pathways activated at low and high NPY concentrations were similar. The mitogenic effect of the peptide at all doses was completely blocked by inhibitors of calcium/calmodulin-dependent kinase II (CaMKII), protein kinase C (PKC), and mitogen-activated protein kinase kinase, MEK1/2. Thus, in VSMCs, NPY-mediated mitogenesis signals primarily via Y1 receptors activating 2 Ca2+-dependent, growth-promoting pathways -- PKC and CaMKII. At the high-affinity peak, these 2 pathways are amplified by Y5 receptor-mediated, calcium-independent inhibition of the adenylyl cyclase - protein kinase A (PKA) pathway. All 3 mechanisms converge to the extracellular signal-regulated kinases (ERK1/2) signaling cascade and lead to VSMC proliferation.
Pons
Jennifer
J
Department of Physiology and Biophysics, Georgetown University Medical Center, Box 571460, Washington, DC 20057-1460, USA.
Kitlinska
Joanna
J
Jacques
Danielle
D
Perreault
Claudine
C
Nader
Moni
M
Everhart
Lindsay
L
Zhang
Ying
Y
Zukowska
Zofia
Z
D000818:Animals; D015153:Blotting, Western; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors / Q000502:physiology; D049109:Cell Proliferation; D005576:Colforsin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000242:Cyclic AMP / Q000096:biosynthesis; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005456:Fluorescent Dyes; D016257:Fura-2; D018613:Microscopy, Confocal; D008938:Mitosis / Q000187:drug effects; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000502:physiology*; D009478:Neuropeptide Y / Q000502:physiology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D051381:Rats; D017476:Receptors, Neuropeptide Y / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*
D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D009478:Neuropeptide Y; D017476:Receptors, Neuropeptide Y; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D016257:Fura-2