alpha(1)-adrenergic receptor stimulation of mitogenesis in human vascular smooth muscle cells: Role of tyrosine protein kinases and calcium in activation of mitogen-activated protein kinase
Zw. Hu et al., alpha(1)-adrenergic receptor stimulation of mitogenesis in human vascular smooth muscle cells: Role of tyrosine protein kinases and calcium in activation of mitogen-activated protein kinase, J PHARM EXP, 290(1), 1999, pp. 28-37
Citations number
44
Categorie Soggetti
Pharmacology & Toxicology
Journal title
JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS
Signaling pathways of many G protein-coupled receptors overlap with those o
f receptor tyrosine kinases. We have found previously that alpha(1)-adrener
gic receptors stimulate DNA synthesis and cell proliferation in human vascu
lar smooth muscle cells; these effects were attenuated by the tyrosine prot
ein kinase (TPK) inhibitor genistein and the mitogen-activated protein kina
se (MAPK) antagonist 2-aminopurine. Experiments were designed to determine
if activation of ct, receptors directly stimulated TPKs and MAPKs in human
vascular smooth muscle cells. Norepinephrine stimulated time- and concentra
tion-dependent tyrosine phosphorylation of multiple proteins, including p52
-, 75-, 85-, 120-, and 145-kDa proteins. Increased TPK activity was demonst
rated in proteins precipitated by an antiphosphotyrosine antibody, both in
autophosphorylation assays and with a peptide substrate. These effects of n
orepinephrine were completely blocked by alpha(1) receptor antagonists. A m
embrane-permeable Ca2+ chelator [1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-te
traacetic acid tetra(acetoxymethyl)ester], completely blocked norepinephrin
e stimulation of phosphorylation of tyrosine proteins, suggesting that intr
acellular Ca2+ plays a critical role in alpha(1) receptor stimulation phosp
horylation of tyrosine proteins. Of the tyrosine-phosphorylated proteins, t
he results suggest that two of them are PLC gamma 1 and adapter protein Shc
. Also, alpha(1) receptor stimulation caused a time-dependent increase in M
APK activity due to increased phosphorylation of p42/44(ERK1/2) The alpha(1
) receptor-mediated activation of MARK was also attenuated by TPK inhibitor
s and intracellular Ca2+ chelator [1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-
tetraacetic acid tetra(acetoxymethyl)ester]. These results suggest that pho
sphorylation of tyrosine proteins and intracellular Ca2+ plays a critical r
ole in alpha(1) receptor-stimulated MARK signaling pathways, potentially co
ntributing to increased DNA synthesis and cell proliferation.