title: Erythropoietin receptor Y479 couples to ERK1/2 activation via recruitment of phospholipase Cgamma.
abstract: Red blood cell development is primarily controlled by erythropoietin (EPO). Several studies have revealed the importance of EPO-R Y343 and Y479 for erythroid cell growth, differentiation, and survival. In order to isolate critical signaling proteins that bind to EPO-R, we initiated a Cloning of Ligand Target (COLT) screen using a murine embryonic day 16 phage library and a biotinylated EPO-R Y343 phosphopeptide. One of the clones isolated encodes Phospholipase C (PLC)gamma1. PLCgamma1 is rapidly tyrosine phosphorylated upon EPO stimulation and associates with EPO-R in an SH2-domain-dependent manner. Although PLCgamma1 bound EPO-R Y343, Y401, Y429, Y431, and Y479 in the COLT screen, PLCgamma1 required Y479 for association with EPO-R in Ba/F3-EPO-R cells. Studies have identified EPO-R Y479 as important for ERK activation. Since PI3-kinase binds EPO-R Y479, one group has suggested that ERK activation downstream of PI3-kinase accounts for the importance of this residue in EPO signaling. However, we show that inhibition of PI3-kinase does not abolish ERK activation. Furthermore, we demonstrate interaction of PLCgamma1 with Grb2 and SOS2. Hence, we have identified a novel adapter function for PLCgamma1 in EPO signaling in which recruitment of PLCgamma1 to EPO-R may lead to activation of the ERK pathway.
authors.affiliation: Division of Stem Cell and Developmetal Biology, Ontario Cancer Institute, University of Toronto, Toronto, Ontario, Canada M5G 2M9.
authors.forename: Adrienne
authors.initials: A
authors.lastname: Halupa
authors.forename: Manprit
authors.initials: M
authors.lastname: Chohan
authors.forename: Natalie H
authors.initials: NH
authors.lastname: Stickle
authors.forename: Bryan K
authors.initials: BK
authors.lastname: Beattie
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Miller
authors.forename: Dwayne L
authors.initials: DL
authors.lastname: Barber
mesh_terms: D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D004920:Erythropoiesis / Q000502:physiology; D004921:Erythropoietin / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D010766:Phosphorylation; D017467:Receptors, Erythropoietin / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D018909:src Homology Domains
chemical_list: D017467:Receptors, Erythropoietin; D004921:Erythropoietin; D048052:Mitogen-Activated Protein Kinase 3