TY - JOUR
T1 - Differential regulation of formyl peptide and platelet-activating factor receptors
T2 - Role of phospholipase Cβ3 phosphorylation by protein kinase A
AU - Ali, Hydar
AU - Sozzani, Silvano
AU - Fisher, Ian
AU - Barr, Alastair J.
AU - Richardson, Ricardo M.
AU - Haribabu, Bodduluri
AU - Snyderman, Ralph
PY - 1998/5/1
Y1 - 1998/5/1
N2 - Formylated peptides (e.g. n-formyl-Met-Leu-Phe (fMLP)) and platelet- activating factor (PAF) mediate chemotactic and cytotoxic responses in leukocytes through receptors coupled to G proteins that activate phospholipase C (PLC). In RBL-2H3 cells, fMLP utilizes a pertussis toxin (ptx)-sensitive G protein to activate PLC, whereas PAF utilizes a ptx- insensitive G protein. Here we demonstrate that fMLP, but not PAF, enhanced intracellular cAMP levels via a ptx-sensitive mechanism. Protein kinase A (PKA) inhibition by H-89 enhanced inositol phosphate formation stimulated by fMLP but not PAF. Furthermore, a membrane-permeable cAMP analog 8-(4- chlorophenylthio)-cAMP (cpt-cAMP) inhibited phosphoinositide hydrolysis and secretion stimulated by fMLP but not PAF. Both cpt-cAMP and fMLP stimulated PLCβ3 phosphorylation in intact RBL cells. The purified catalytic subunit of PKA phosphorylated PLCβ3 immunoprecipitated from RBL cell lysate. Pretreatment of intact cells with cpt-cAMP and fMLP, but not PAF, resulted in an inhibition of subsequent PLCβ3 phosphorylation by PKA in vitro. These data demonstrate that fMLP receptor, which couples to a ptx-sensitive G protein, activates both PLC and cAMP production. The resulting PKA activation phosphorylates PLCβ3 and appears to block the ability of G(βγ) to activate PLC. Thus, both fMLP and PAF generate stimulatory signals for PLCβ3, but only fMLP produces a PKA-dependent inhibitory signal. This suggests a novel mechanism for the bidirectional regulation of receptors which activate PLC by ptx-sensitive G proteins.
AB - Formylated peptides (e.g. n-formyl-Met-Leu-Phe (fMLP)) and platelet- activating factor (PAF) mediate chemotactic and cytotoxic responses in leukocytes through receptors coupled to G proteins that activate phospholipase C (PLC). In RBL-2H3 cells, fMLP utilizes a pertussis toxin (ptx)-sensitive G protein to activate PLC, whereas PAF utilizes a ptx- insensitive G protein. Here we demonstrate that fMLP, but not PAF, enhanced intracellular cAMP levels via a ptx-sensitive mechanism. Protein kinase A (PKA) inhibition by H-89 enhanced inositol phosphate formation stimulated by fMLP but not PAF. Furthermore, a membrane-permeable cAMP analog 8-(4- chlorophenylthio)-cAMP (cpt-cAMP) inhibited phosphoinositide hydrolysis and secretion stimulated by fMLP but not PAF. Both cpt-cAMP and fMLP stimulated PLCβ3 phosphorylation in intact RBL cells. The purified catalytic subunit of PKA phosphorylated PLCβ3 immunoprecipitated from RBL cell lysate. Pretreatment of intact cells with cpt-cAMP and fMLP, but not PAF, resulted in an inhibition of subsequent PLCβ3 phosphorylation by PKA in vitro. These data demonstrate that fMLP receptor, which couples to a ptx-sensitive G protein, activates both PLC and cAMP production. The resulting PKA activation phosphorylates PLCβ3 and appears to block the ability of G(βγ) to activate PLC. Thus, both fMLP and PAF generate stimulatory signals for PLCβ3, but only fMLP produces a PKA-dependent inhibitory signal. This suggests a novel mechanism for the bidirectional regulation of receptors which activate PLC by ptx-sensitive G proteins.
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U2 - 10.1074/jbc.273.18.11012
DO - 10.1074/jbc.273.18.11012
M3 - Article
C2 - 9556582
AN - SCOPUS:0032079831
VL - 273
SP - 11012
EP - 11016
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 18
ER -