The low M(r) protein-tyrosine phosphatase is involved in Rho-mediated cytoskeleton rearrangement after integrin and platelet-derived growth factor stimulation.
The low molecular weight protein-tyrosine phosphatase (LMW-PTP) is an enzyme that is involved in the early events of platelet-derived growth factor (PDGF) receptor signal transduction. In fact, LMW-PTP is able to specifically bind and dephosphorylate activated PDGF receptor, thus modulating PDGF-induced mitogenesis. In particular, LMW-PTP is involved in pathways that regulate the transcription of the immediately early genes myc and fos in response to growth factor stimulation. Recently, we have found that LMW-PTP exists constitutively in cytosolic and cytoskeleton-associated localization and that, after PDGF stimulation, c-Src is able to bind and phosphorylate LMW-PTP only in the cytoskeleton-associated fraction. As a consequence of its phosphorylation, LMW-PTP increases its catalytic activity about 20-fold. In this study, our interest was to investigate the role of LMW-PTP phosphorylation in cellular response to PDGF stimulation. To address this issue, we have transfected in NIH-3T3 cells a mutant form of LMW-PTP in which the c-Src phosphorylation sites (Tyr(131) and Tyr(132)) were mutated to alanine. We have established that LMW-PTP phosphorylation by c-Src after PDGF treatment strongly influences both cell adhesion and migration. In addition, we have discovered a new LMW-PTP substrate localized in the cytoskeleton that becomes tyrosine-phosphorylated after PDGF treatment: p190Rho-GAP. Hence, LMW-PTP plays multiple roles in PDGF receptor-mediated mitogenesis, since it can bind and dephosphorylate PDGF receptor, and, at the same time, the cytoskeleton-associated LMW-PTP, through the regulation of the p190Rho-GAP phosphorylation state, controls the cytoskeleton rearrangement in response to PDGF stimulation.
Chiarugi
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P
Dipartimento di Scienze Biochimiche, Università di Firenze, 50134 Firenze, Italy.
Cirri
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P
Taddei
L
L
Giannoni
E
E
Camici
G
G
Manao
G
G
Raugei
G
G
Ramponi
G
G
D016475:3T3 Cells; D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D003599:Cytoskeleton / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D004268:DNA-Binding Proteins; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D016023:Integrins / Q000502:physiology*; D051379:Mice; D008970:Molecular Weight; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000502:physiology*; D010750:Phosphoproteins / Q000502:physiology*; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins; D013379:Substrate Specificity
C513041:Arhgap35 protein, mouse; C513042:Arhgap5 protein, mouse; D004268:DNA-Binding Proteins; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D016023:Integrins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D010982:Platelet-Derived Growth Factor; D012097:Repressor Proteins; D017027:Protein Tyrosine Phosphatases