Oxidative Inhibition of Protein Phosphatase 2A Activity: Role of Catalytic Subunit Disulfides

Abstract

A molecular basis for the inhibition of brain protein phosphatase 2A (PP2A) activity by oxidative stress was examined in a high-speed supernatant (HSS) fraction from rat cerebral cortex. PP2A activity was subject to substantial disulfide reducing agent-reversible inhibition in the HSS fraction. Results of gel electrophoresis support the conclusions that inhibition of PP2A activity was associated with the both the disulfide cross-linking of the catalytic subunit (PP2A(C)) of the enzyme to other brain proteins and with the formation of an apparent novel intramolecular disulfide bond in PP2A(C). Additional findings that the vicinal dithiol cross-linking reagent phenylarsine oxide (PAO) produced a potent dithiothreitol-reversible inhibition of PP2A activity suggest that the cross-linking of PP2A(C) vicinal thiols to form an intramolecular disulfide bond may be sufficient to inhibit PP2A activity under oxidative stress. We propose that the dithiol-disulfide equilibrium of a vicinal thiol pair of PP2A(C) may confer redox sensitivity on cellular PP2A.

Proinflammatory Cytokine IL-1β Stimulates IL-8 Synthesis in Mast Cells via a Leukotriene B4 Receptor 2-Linked Pathway, Contributing to Angiogenesis

“…Scale bars, 10 mm. Original magnification 3400. subunit of PP2A under oxidative stress is sufficient to inhibit its activity (56). Similarly, superoxide and hydrogen peroxide induce the inactivation of PP2B by forming disulfide bonds between redox-sensitive cysteine residues (57,58).…”

Inhibition of Protein Phosphatase 2A (PP2A) Prevents Mcl-1 Protein Dephosphorylation at the Thr-163/Ser-159 Phosphodegron, Dramatically Reducing Expression in Mcl-1-amplified Lymphoma Cells

“…Below the Western blot for these proteins is the Coomassie Blue-stained SDS-PAGE gel showing the GST proteins used for pulldown. The electrophoretic migration of PP2A/C reflects the fact that this protein undergoes disulfide bridge formation in the presence of DTT resulting in a higher molecular weight band (input samples in third and sixth lanes on the upper Western blot), which reverts to the unmodified form when the concentration of DTT is reduced (first and fourth lanes) (68). Multiple bands can also occur with PP2A due to oxidation-mediated modifications as described (68 -70).…”

An Improved Phenylarsine Oxide-Affinity Method Identifies Triose Phosphate Isomerase as a Candidate Redox Receptor Protein

“…We speculate that reversible oxidation of the PAO-binding thiols of TPI may confer on this enzyme a function as redox receptor protein that confers sensitivity to oxidative and nitrosative stress on cellular metabolism. Future work will examine in greater detail the nature of the PAO-binding thiols of TPI and explore the oxidation of the PAO-binding thiols of lower abundance neuronal regulatory proteins such as protein phosphatase 2A, which our recent findings [24] suggest may contain redox-active vicinal thiols.…”