Two vicinal cysteines confer a peculiar redox regulation to low molecular weight protein tyrosine phosphatase in response to platelet-derived growth factor receptor stimulation.
Low molecular weight protein tyrosine phosphatase (LMW-PTP) is an enzyme involved in platelet-derived growth factor (PDGF)-induced mitogenesis and cytoskeleton rearrangement because it is able to bind and dephosphorylate the activated receptor. LMW-PTP presents two cysteines in positions 12 and 17, both belonging to the catalytic pocket; this is a unique feature of LMW-PTP among all protein tyrosine phosphatases. Our previous results demonstrated that in vitro LMW-PTP is oxidized by either H(2)O(2) or nitric oxide with the formation of a disulfide bond between Cys-12 and Cys-17. This oxidation leads to reversible enzyme inactivation because treatment with reductants permits catalytic activity rescue. In the present study we investigated the in vivo inactivation of LMW-PTP by either extracellularly or intracellularly generated H(2)O(2), evaluating its action directly on its natural substrate, PDGF receptor. LMW-PTP is oxidized and inactivated by exogenous oxidative stress and recovers its activity after oxidant removal. LMW-PTP is oxidized also during PDGF signaling, very likely upon PDGF-induced H(2)O(2) production, and recovers its activity within 40 min. Our results strongly suggest that reversibility of in vivo LMW-PTP oxidation is glutathione-dependent. In addition, we propose an intriguing and peculiar role of Cys-17 in the formation of a S-S intramolecular bond, which protects the catalytic Cys-12 from further and irreversible oxidation. On the basis of our results we propose that the presence of an additional cysteine near the catalytic cysteine could confer to LMW-PTP the ability to rapidly recover its activity and finely regulate PDGF receptor activation during both extracellularly and intracellularly generated oxidative stress.
Chiarugi
P
P
Dipartimento di Scienze Biochimiche, Universitá degli Studi di Firenze, 50134 Firenze, Italy.
Fiaschi
T
T
Taddei
M L
ML
Talini
D
D
Giannoni
E
E
Raugei
G
G
Ramponi
G
G
D016475:3T3 Cells; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002384:Catalysis; D002460:Cell Line; D016895:Culture Media, Serum-Free / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry*; D004789:Enzyme Activation; D005978:Glutathione / Q000737:chemistry; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007527:Isoenzymes; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D017382:Reactive Oxygen Species / Q000378:metabolism; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism
D016895:Culture Media, Serum-Free; D007527:Isoenzymes; D011518:Proto-Oncogene Proteins; D017382:Reactive Oxygen Species; D014443:Tyrosine; D006861:Hydrogen Peroxide; D017479:Receptors, Platelet-Derived Growth Factor; C490429:ACP1 protein, human; C490428:Acp1 protein, mouse; D017027:Protein Tyrosine Phosphatases; D005978:Glutathione; D003545:Cysteine; D010100:Oxygen