Aging is associated with dimerization and inactivation of the brain-enriched tyrosine phosphatase STEP.
The STriatal-Enriched tyrosine Phosphatase (STEP) is involved in the etiology of several age-associated neurologic disorders linked to oxidative stress and is also known to play a role in neuroprotection by modulating glutamatergic transmission. However, the possible effect of aging on STEP level and activity in the brain is still unclear. In this study, using young (1 month), adult (4 months), and aged (18 months) rats, we show that aging is associated with increase in dimerization and loss of activity of STEP. Increased dimerization of STEP is primarily observed in the cortex and hippocampus and is associated with depletion of both reduced and total glutathione levels, suggesting an increase in oxidative stress. Consistent with this interpretation, studies in cell culture models of glutathione depletion and oxidative stress also demonstrate formation of dimers and higher order oligomers of STEP that involve intermolecular disulfide bond formation between multiple cysteine residues. Conversely, administration of N-acetyl cysteine, a major antioxidant that enhances glutathione biosynthesis, attenuates STEP dimerization both in the cortex and hippocampus. The findings indicate that loss of this intrinsic protective response pathway with age-dependent increase in oxidative stress may be a contributing factor for the susceptibility of the brain to age-associated neurologic disorders.
Department of Neurology, University of New Mexico Health Sciences Center, Albuquerque, NM, USA.
Sathyanarayanan
S
Rajagopal
Department of Neurology, University of New Mexico Health Sciences Center, Albuquerque, NM, USA.
Ishani
I
Deb
Department of Neurology, University of New Mexico Health Sciences Center, Albuquerque, NM, USA.
Ranjana
R
Poddar
Department of Neurology, University of New Mexico Health Sciences Center, Albuquerque, NM, USA; Department of Neurosciences, University of New Mexico Health Sciences Center, Albuquerque, NM, USA. Electronic address: spaul@salud.unm.edu.
Surojit
S
Paul
D000111:Acetylcysteine / Q000494:pharmacology; D000375:Aging / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001921:Brain / Q000201:enzymology / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation; D005971:Glutamates / Q000502:physiology; D005978:Glutathione / Q000378:metabolism; D009422:Nervous System Diseases / Q000209:etiology*; D000066829:Neuroprotection; D018384:Oxidative Stress / Q000502:physiology; D055503:Protein Multimerization; D054558:Protein Tyrosine Phosphatases, Non-Receptor / Q000378:metabolism / Q000502:physiology*; D017207:Rats, Sprague-Dawley; D009435:Synaptic Transmission / Q000235:genetics
D000975:Antioxidants; D005971:Glutamates; D054558:Protein Tyrosine Phosphatases, Non-Receptor; C489931:Ptpn5 protein, rat; D005978:Glutathione; D000111:Acetylcysteine
Aging; Dimerization; Glutathione; N-acetyl cysteine; STEP; Tyrosine phosphatase