Phosphatase and tensin homolog (PTEN) belongs to the protein tyrosine phosphatase (PTP) family and was initially identified as a tumor suppressor with a specific role in regulating cell growth. The structure of human PTEN consists of an N-terminal-phosphatidylinositol (4,5)-bisphosphate (PIP2)-binding/phosphatase catalytic domain followed by a C2-lipid-binding domain, which enables its membrane-associated function, a C-terminal tail domain and a PDZ-binding domain. The distinctive feature phosphatase function of PTEN, in comparison with other PTPs, is counteracting the activity of class I phosphoinositide 3-kinases (PI3Ks) through the dephosphorylation of phosphatidylinositol-3,4,5-triphosphate (PIP3) to PIP2 [
1,
2,
3,
4]. Through this mechanism, PTEN acts as a suppressor of the phosphoinositide 3-kinases /protein kinase B (PI3K/AKT) pathway. Since the PI3K/AKT signaling pathway promotes protein synthesis, cell survival, proliferation, and migration [
5,
6], PTEN dysfunction can contribute to the development of certain hereditary tumorigenesis disorders such as Cowden syndrome, Proteus syndrome, Bannayan–Riley–Ruvalcaba syndrome, and Lhermitte-Duclos disease [
7], as well as various cancers including breast [
8], thyroid [
9], endometrium [
10], prostate [
11], brain [
12], and skin cancer [
13].
PTEN expression can be regulated through genetic, epigenetic, post-transcriptional, and post-translational mechanisms that influence the PTEN gene, mRNA, and protein [
14]. Kinases such as Glycogen Synthase Kinase GSK3, Casein Kinase CK2, and Serine Threonine Kinase STK11 can inactivate PTEN by phosphorylating serine and threonine residues on the C-terminal tail region. Biperoxovanadium compounds are extensively used as specific PTEN inhibitors [
5]. The elevated PI3K/AKT signaling pathway has been demonstrated to be beneficial in physiological processes that require cell regeneration. Therefore, inhibiting PTEN, a negative regulator of the PI3K/AKT pathway, has been considered a prospective therapy for neurodegenerative diseases, ischemia, infection, and insulin-resistant metabolic disorders [
14].
Like other members of the PTP family that contain a cysteine residue in their active site, PTEN can undergo oxidative inactivation by reactive oxygen species (ROS) [
15]. ROS are generated through endogenous sources such as NADPH oxidase (NOX), nitric oxide synthase (NOS), xanthine oxidase, aldehyde oxidase, cyclo-oxygenase, cytochrome P450 2E1 and electron leakage from mitochondria, as well as exogenous sources such as smoke, ultraviolet light, radiation and drugs [
16,
17]. Superoxide (O
2-) can react with nitric oxide (NO) to form ONOO
- or be transformed to hydrogen peroxide (H
2O
2) by superoxide dismutase (SOD), vitamin E, or vitamin C. Oxidative inactivation of PTEN, which can serve as a physiological regulatory mechanism is executed by ROS not only from oxidative stress but also from cellular signaling transductions, for example, growth factor stimulation-derived NOXs [
18]. A growing body of evidence has indicated that ROS are produced and utilized in physiological circumstances to function as significant signaling messengers, facilitating the coordination of various fundamental processes, including inflammation, survival, proliferation, differentiation, apoptosis, signal transduction, and other critical events [
19,
20,
21,
22,
23]. The ROS that have such cellular physiological functions are predominantly generated at the cell's plasma membrane and endomembrane through the activity of NOXs [
24]. H
2O
2 is the major ROS responsible for initiating redox-dependent signaling within the cell's cytosol [
25], and the source of this physiological H
2O
2 is also related to the activities of membrane-associated complex NOXs and specialized cells such as phagocytes [
26] [
27]. Lee
et al. were the first to demonstrate the reversible inactivation of PTEN by H
2O
2. During this process, the Cys124 catalytic residue in the active site of PTEN is oxidized and forms a disulfide bond with Cys71 [
28]. Furthermore, the oxidative inhibition of PTEN by H
2O
2 has been experimentally demonstrated to increase the PI3K/AKT signaling pathway [
29]. Peroxynitrite (ONOO
-) can also oxidize cysteine residues within the PTPs, leading to such oxidative inhibition. This process might be considerably faster and more effective in inactivating PTPs at lower concentrations than H
2O
2. This suggests that peroxynitrite may be the primary biological mediator responsible for PTPs’ inactivation, consequently enhancing tyrosine phosphorylation in situations related to oxidative stress [
30]. However, the impact of peroxynitrite on phosphotyrosine-dependent signaling can manifest as either activation or inhibition. The upregulation of this signaling could arise from PTPs’ inactivation by a low concentration of peroxynitrite, and this feature has typical characteristics of cell signaling, being transient and reversible. Yet, how peroxynitrite affects the PI3K/AKT pathway is still controversial [
31].
The oxidative inactivation of PTEN leads to an increase in PI3K/AKT downstream signaling, which subsequently induces its physiological effects [
29,
32,
33]. Recently, bicarbonate/carbon dioxide (HCO
3-/CO
2) has emerged as a pivotal factor in promoting the oxidative reactivity of H
2O
2 by creating a higher reactive form called peroxymonocarbonate (HCO
4-) [
34,
35,
36]. Since there are several meticulous and comprehensive reviews about the regulators of PTEN and their impacts on the PI3K/AKT signaling pathway, as well as their implications in physiology and diseases, we focus on the role of oxidative inhibition of PTEN in physiological processes. In addition, we also mention the role of bicarbonate/carbon dioxide in the oxidation of PTPs by H
2O
2.