Bicarbonate is essential for protein-tyrosine phosphatase 1B (PTP1B) oxidation and cellular signaling through EGF-triggered phosphorylation cascades

Abstract

Edited by Ruma BanerjeeProtein-tyrosine phosphatases (PTPs) counteract protein tyrosine phosphorylation and cooperate with receptor-tyrosine kinases in the regulation of cell signaling. PTPs need to undergo oxidative inhibition for activation of cellular cascades of protein-tyrosine kinase phosphorylation following growth factor stimulation. It has remained enigmatic how such oxidation can occur in the presence of potent cellular reducing systems. Here, using in vitro biochemical assays with purified, recombinant protein, along with experiments in the adenocarcinoma cell line A431, we discovered that bicarbonate, which reacts with H 2 O 2 to form the more reactive peroxymonocarbonate, potently facilitates H 2 O 2 -mediated PTP1B inactivation in the presence of thioredoxin reductase 1 (TrxR1), thioredoxin 1 (Trx1), and peroxiredoxin 2 (Prx2) together with NADPH. The cellular experiments revealed that intracellular bicarbonate proportionally dictates total protein phosphotyrosine levels obtained after stimulation with epidermal growth factor (EGF) and that bicarbonate levels directly correlate with the extent of PTP1B oxidation. In fact, EGF-induced cellular oxidation of PTP1B was completely dependent on the presence of bicarbonate. These results provide a plausible mechanism for PTP inactivation during cell signaling and explain long-standing observations that growth factor responses and protein phosphorylation cascades are intimately linked to the cellular acid-base balance.

The Emerging Role of Rab5 in Membrane Receptor Trafficking and Signaling Pathways

“…Deletion of PTP1B promotes the phosphorylation of NSF and reduces the formation of phosphatidylinositol 3-phosphate-positive early endosomes and the activation of Rab5, resulting in inhibition of c-MET and EGF receptor transport and degradation [62]. Knockdown of NSF influences signal transduction and recirculation of c-MET, EGF receptor, integrin, and IGF-1 receptor, leading to restraining of the receptors in vesicles instead of entering the nucleus and an ultimately sustained activation of c-MET/MEK1/2 and EGF receptor/ MEK1/2 signaling pathways [63,64].…”

Role of Glutaredoxin-1 and Glutathionylation in Cardiovascular Diseases

“…These reactive cysteine thiolates can exhibit a reactivity resembling that of a thiol-peroxidase and thus react with oxidants such as hydrogen peroxide. However, recent experiments suggest that hydrogen peroxide may not react directly; and peroxymonocarbonate is a reactive intermediate to oxidize cysteine of proteins [29]. The oxidation of the thiolate transiently produces sulfenic acid (R-SOH) that reacts with GSH leading to GSylation [30][31][32].…”

Tracking isotopically labeled oxidants using boronate-based redox probes

“…6a) (9,52,53). Formation of this species has been implicated, for example, in the enhanced hyperoxidation of cellular peroxiredoxins and protein tyrosine phosphatase 1B (PTP1B)mediated signaling cascade observed in the presence of bicarbonate (12,(54)(55)(56). Recently, it was shown that the rate of oxidation of the coumarin boronate probe in the presence of H2O2 is increased after the addition of bicarbonate (10).…”

“…Both superoxide and H2O2 are relatively slow reacting and/or weak oxidants (4-6) but in biological systems can be converted to more reactive species ( Fig. 1), including peroxynitrite (7,8), peroxymonocarbonate (HCO4 -) (9,10), or hypochlorous acid (HOCl) (11), resulting in enhanced redox signaling and/or damage to cell components (5,12,13). Due to the short lifetime of most ROS in biological settings, detection and quantitative analyses of those species have remained a challenge, and development of new probes for redox biology is an active area of research.…”