The beta(2)-adrenergic receptor mediates extracellular signal-regulated kinase activation via assembly of a multi-receptor complex with the epidermal growth factor receptor.
Many G protein-coupled receptors (GPCRs) activate MAP kinases by stimulating tyrosine kinase signaling cascades. In some systems, GPCRs stimulate tyrosine phosphorylation by inducing the "transactivation" of a receptor tyrosine kinase (RTK). The mechanisms underlying GPCR-induced RTK transactivation have not been clearly defined. Here we report that GPCR activation mimics growth factor-mediated stimulation of the epidermal growth factor receptor (EGFR) with respect to many facets of RTK function. beta(2)-Adrenergic receptor (beta(2)AR) stimulation of COS-7 cells induces EGFR dimerization, tyrosine autophosphorylation, and EGFR internalization. Coincident with EGFR transactivation, isoproterenol exposure induces the formation of a multireceptor complex containing both the beta(2)AR and the "transactivated" EGFR. beta(2)AR-mediated EGFR phosphorylation and subsequent beta(2)AR stimulation of extracellular signal-regulated kinase (ERK) 1/2 are sensitive to selective inhibitors of both EGFR and Src kinases, indicating that both kinases are required for EGFR transactivation. beta(2)AR-dependent signaling to ERK1/2, like direct EGF stimulation of ERK1/2 activity, is sensitive to inhibitors of clathrin-mediated endocytosis, suggesting that signaling downstream of both the EGF-activated and the GPCR-transactivated EGFRs requires a productive engagement of the complex with the cellular endocytic machinery. Thus, RTK transactivation is revealed to be a process involving both association of receptors of distinct classes and the interaction of the transactivated RTK with the cells endocytic machinery.
Maudsley
S
S
Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.
Pierce
K L
KL
Zamah
A M
AM
Miller
W E
WE
Ahn
S
S
Daaka
Y
Y
Lefkowitz
R J
RJ
Luttrell
L M
LM
D000818:Animals; D019556:COS Cells; D002966:Clathrin / Q000502:physiology; D004705:Endocytosis / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism / Q000502:physiology*; D015533:Transcriptional Activation
D002966:Clathrin; D008024:Ligands; D018343:Receptors, Adrenergic, beta-2; D066246:ErbB Receptors; D020928:Mitogen-Activated Protein Kinases