Optimal lysophosphatidic acid-induced DNA synthesis and cell migration but not survival require intact autophosphorylation sites of the epidermal growth factor receptor.
Lysophosphatidic acid (LPA)-elicited transphosphorylation of receptor tyrosine kinases has been implicated in mediating extracellular signal-regulated kinase (ERK) 1/2 activation, which is necessary for LPA-induced cell proliferation, migration, and survival. B82L cells lack epidermal growth factor receptor (EGFR) but express LPA(1-3), platelet-derived growth factor (PDGF), ErbB2, and insulin-like growth factor receptor transcripts, yet LPA caused no detectable transphosphorylation of these receptor tyrosine kinases. LPA equally protected B82L cells, or transfectants expressing EGFR, the kinase dead EGFR(K721A), EGFR(Y5F) receptor mutant, which lacks five autophosphorylation sites, or EGFR(Y845F), which lacks the Src phosphorylation site from tumor necrosis factor-alpha-induced apoptosis. In contrast, LPA-elicited DNA synthesis and migration were augmented in cells expressing EGFR, EGFR(K721A), or EGFR(Y845F), but not EGFR(Y5F), although the PDGF responses were indistinguishable. LPA-induced transphosphorylation of the EGFR, ErbB2, or PDGF receptor was not required for its antiapoptotic effect. EGFR with or without intrinsic kinase activity or without the Src-phosphorylation site augmented, but was not required for, LPA-elicited cell proliferation or migration. In B82L cells, augmentation of these two LPA responses required intact autophosphorylation sites because among the four EGFR mutants, only cells expressing the EGFR(Y5F) mutant showed no enhancement. In EGFR(Y5F)-expressing cells, LPA failed to elicit tyrosine phosphorylation of Src homologous and collagen protein (SHC) and caused only a modest increase in ERK1/2 phosphorylation similar to that in wild-type B82L cells. The present data pinpoint the lack of importance of the intrinsic kinase activity in contrast to the importance of autophosphorylation sites of the EGFR for SHC phosphorylation in the enhancement of select ERK1/2-dependent LPA responses.
Deng
Wenlin
W
Department of Physiology, The University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
Poppleton
Helen
H
Yasuda
Satoshi
S
Makarova
Natalia
N
Shinozuka
Yoriko
Y
Wang
De-An
DA
Johnson
Leonard R
LR
Patel
Tarun B
TB
Tigyi
Gabor
G
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology*; D002470:Cell Survival / Q000502:physiology*; D004247:DNA / Q000096:biosynthesis / Q000378:metabolism*; D053938:DNA Fragmentation; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005419:Flavonoids / Q000378:metabolism; D006801:Humans; D008246:Lysophospholipids / Q000378:metabolism*; D051379:Mice; D037342:Pertussis Toxin / Q000378:metabolism; D010766:Phosphorylation; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D004791:Enzyme Inhibitors; D005419:Flavonoids; D008246:Lysophospholipids; D014409:Tumor Necrosis Factor-alpha; D004247:DNA; D037342:Pertussis Toxin; D066246:ErbB Receptors; D020794:Receptor Protein-Tyrosine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; C032881:lysophosphatidic acid; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one