Dissociation of the nuclear WWOX/TRAF2 switch renders UV/cold shock-mediated nuclear bubbling cell death at low temperatures.

BACKGROUND: Normal cells express functional tumor suppressor WW domain-containing oxidoreductase (WWOX), designated WWOXf. UV irradiation induces WWOXf cells to undergo bubbling cell death (BCD) - an event due to the accumulation of nuclear nitric oxide (NO) gas that forcefully pushes the nuclear and cell membranes to form one or two bubbles at room temperature (22 °C) and below. In contrast, when WWOX-deficient or -dysfunctional (WWOXd) cells are exposed to UV and/or cold shock, the cells undergo nuclear pop-out explosion death (POD). We aimed to determine the morphological and biochemical changes in WWOXf cells during BCD versus apoptosis. METHODS: WWOXf and WWOXd cells were exposed to UV followed by measuring BCD or POD by time-lapse microscopy and/or time-lapse holographic microscopy at 4, 22, or 37 °C to visualize morphological changes. Live cell stains were used to measure the kinetics of nitric oxide (NO) production and Ca2+ influx. Extent of cell death was measured by uptake of propidium iodide and by internucleosomal DNA fragmentation using agarose gel electrophoresis. RESULTS: WWOXf cells were exposed to UV and then cold shock, or cold shock and then UV, and cultured at 4, 10, and 22 °C, respectively. Initially, UV induced calcium influx and NO production, which led to nuclear bubbling and final death. Cold shock pretreatment completely suppressed UV-mediated bubbling at 37 °C, so the UV/cold shock-treated cells underwent apoptosis. Without cold shock, UV only induced bubbling at all temperatures, whereas the efficiency of bubbling at 37 °C was reduced by greater than 50%. Morphologically, the WWOXf cell height or thickness was significantly increased during cell division or apoptosis, but the event did not occur in BCD. In comparison, when WWOXd cancer cells received UV or UV/cold shock, these cells underwent NO-independent POD. UV/cold shock effectively downregulated the expression of many proteins such as the housekeeping α-tubulin (> 70%) and ß-actin (< 50%), and cortactin (> 70%) in WWOXf COS7 cells. UV/cold shock induced relocation of α-tubulin to the nucleus and nuclear bubbles in damaged cells. UV induced co-translocation of the WWOX/TRAF2 complex to the nuclei, in which the prosurvival TRAF2 blocked the proapoptotic WWOX via its zinc finger domain. Without WWOX, TRAF2 did not relocate to the nuclei. Cold shock caused the dissociation of the WWOX/TRAF2 complex in the nucleus needed for BCD. In contrast, the formation of the WWOX/TRAF2 complex, plus p53, was strengthened at 37 °C required for apoptosis. CONCLUSIONS: The temperature-sensitive nuclear WWOX/TRAF2 complex acts as a molecular switch, whose dissociation favors BCD at low temperatures, and the association supports apoptosis at 37 °C in UV-treated WWOXf cells.

Therapeutic Zfra4-10 or WWOX7-21 Peptide Induces Complex Formation of WWOX with Selective Protein Targets in Organs that Leads to Cancer Suppression and Spleen Cytotoxic Memory Z Cell Activation In Vivo.

Synthetic Zfra4-10 and WWOX7-21 peptides strongly suppress cancer growth in vivo. Hypothetically, Zfra4-10 binds to the membrane Hyal-2 of spleen Z cells and activates the Hyal-2/WWOX/SMAD4 signaling for cytotoxic Z cell activation to kill cancer cells. Stimulation of membrane WWOX in the signaling complex by a WWOX epitope peptide, WWOX7-21, is likely to activate the signaling. Here, mice receiving Zfra4-10 or WWOX7-21 peptide alone exhibited an increased binding of endogenous tumor suppressor WWOX with ERK, C1qBP, NF-κB, Iba1, p21, CD133, JNK1, COX2, Oct4, and GFAP in the spleen, brain, and/or lung which led to cancer suppression. However, when in combination, Zfra4-10 and WWOX7-21 reduced the binding of WWOX with target proteins and allowed tumor growth in vivo. In addition to Zfra4-10 and WWOX7-21 peptides, stimulating the membrane Hyal-2/WWOX complex with Hyal-2 antibody and sonicated hyaluronan (HAson) induced Z cell activation for killing cancer cells in vivo and in vitro. Mechanistically, Zfra4-10 binds to membrane Hyal-2, induces dephosphorylation of WWOX at pY33 and pY61, and drives Z cell activation for the anticancer response. Thus, Zfra4-10 and WWOX7-21 peptides, HAson, and the Hyal-2 antibody are of therapeutic potential for cancer suppression.

WWOX Possesses N-Terminal Cell Surface-Exposed Epitopes WWOX7-21 and WWOX7-11 for Signaling Cancer Growth Suppression and Prevention In Vivo.

Membrane hyaluronidase Hyal-2 supports cancer cell growth. Inhibition of Hyal-2 by specific antibody against Hyal-2 or pY216-Hyal-2 leads to cancer growth suppression and prevention in vivo. By immunoelectron microscopy, tumor suppressor WWOX is shown to be anchored, in part, in the cell membrane by Hyal-2. Alternatively, WWOX undergoes self-polymerization and localizes in the cell membrane. Proapoptotic pY33-WWOX binds Hyal-2, and TGF-ß induces internalization of the pY33-WWOX/Hyal-2 complex to the nucleus for causing cell death. In contrast, when pY33 is downregulated and pS14 upregulated in WWOX, pS14-WWOX supports cancer growth in vivo. Here, we investigated whether membrane WWOX receives extracellular signals via surface-exposed epitopes, especially at the S14 area, that signals for cancer growth suppression and prevention. By using a simulated 3-dimentional structure and generated specific antibodies, WWOX epitopes were determined at amino acid #7 to 21 and #286 to 299. Synthetic WWOX7-21 peptide, or truncation to 5-amino acid WWOX7-11, significantly suppressed and prevented the growth and metastasis of melanoma and skin cancer cells in mice. Time-lapse microscopy revealed that WWOX7-21 peptide potently enhanced the explosion and death of 4T1 breast cancer stem cell spheres by ceritinib. This is due to rapid upregulation of proapoptotic pY33-WWOX, downregulation of prosurvival pERK, prompt increases in Ca2+ influx, and disruption of the IkBα/WWOX/ERK prosurvival signaling. In contrast, pS14-WWOX7-21 peptide dramatically increased cancer growth in vivo and protected cancer cells from ceritinib-mediated apoptosis in vitro, due to a prolonged ERK phosphorylation. Further, specific antibody against pS14-WWOX significantly enhanced the ceritinib-induced apoptosis. Together, the N-terminal epitopes WWOX7-21 and WWOX7-11 are potent in blocking cancer growth in vivo. WWOX7-21 and WWOX7-11 peptides and pS14-WWOX antibody are of therapeutic values in suppressing and preventing cancer growth in vivo.

A p53/TIAF1/WWOX triad exerts cancer suppression but may cause brain protein aggregation due to p53/WWOX functional antagonism.

BACKGROUND: Tumor suppressor WWOX physically binds p53 and TIAF1 and together induces apoptosis and tumor suppression. To understand the molecular action, here we investigated the formation of WWOX/TIAF1/p53 triad and its regulation of cancer cell migration, anchorage-independent growth, SMAD promoter activation, apoptosis, and potential role in neurodegeneration. METHODS: Time-lapse microscopy was used to measure the extent of cell migration. Protein/protein interactions were determined by co-immunoprecipitation, FRET microscopy, and yeast two-hybrid analysis. The WWOX/TIAF1/p53 triad-mediated cancer suppression was determined by measuring the extent of cell migration, anchorage-independent growth, SMAD promoter activation, and apoptosis. p53-deficient lung cancer cell growth in nude mice was carried out to assess the tumor suppressor function of ectopic p53 and/or WWOX. RESULTS: Wwox-deficient MEF cells exhibited constitutive Smad3 and p38 activation and migrated individually and much faster than wild type cells. TGF-ß increased the migration of wild type MEF cells, but significantly suppressed Wwox knockout cell migration. While each of the triad proteins is responsive to TGF-ß stimulation, ectopically expressed triad proteins suppressed cancer cell migration, anchorage-independent growth, and SMAD promoter activation, as well as caused apoptosis. The effects are due in part to TIAF1 polymerization and its retention of p53 and WWOX in the cytoplasm. p53 and TIAF1 were effective in suppressing anchorage-independent growth, and WWOX ineffective. p53 and TIAF1 blocked WWOX or Smad4-regulated SMAD promoter activation. WWOX suppressed lung cancer NCI-H1299 growth and inhibited splenomegaly by inflammatory immune response, and p53 blocked the event in nude mice. The p53/WWOX-cancer mice exhibited BACE upregulation, APP degradation, tau tangle formation, and amyloid ß generation in the brain and lung. CONCLUSION: The WWOX/TIAF1/p53 triad is potent in cancer suppression by blocking cancer cell migration, anchorage-independent growth and SMAD promoter activation, and causing apoptosis. Yet, p53 may functionally antagonize with WWOX. p53 blocks WWOX inhibition of inflammatory immune response induced by cancer, and this leads to protein aggregation in the brain as seen in the Alzheimer's disease and other neurodegeneration.

Zfra restores memory deficits in Alzheimer's disease triple-transgenic mice by blocking aggregation of TRAPPC6AΔ, SH3GLB2, tau, and amyloid ß, and inflammatory NF-κB activation.

INTRODUCTION: Zinc finger-like protein that regulates apoptosis (Zfra) is a naturally occurring 31-amino-acid protein. Synthetic peptides Zfra1-31 and Zfra4-10 are known to effectively block the growth of many types of cancer cells. METHODS: Ten-month-old triple-transgenic (3×Tg) mice for Alzheimer's disease (AD) received synthetic Zfra peptides via tail vein injections, followed by examining restoration of memory deficits. RESULTS: Zfra significantly downregulated TRAPPC6AΔ, SH3GLB2, tau, and amyloid ß (Αß) aggregates in the brains of 3×Tg mice and effectively restored their memory capabilities. Zfra inhibited melanoma-induced neuronal death in the hippocampus and plaque formation in the cortex. Mechanistically, Zfra blocked the aggregation of amyloid ß 42 and many serine-containing peptides in vitro, suppressed tumor necrosis factor-mediated NF-κB activation, and bound cytosolic proteins for accelerating their degradation in ubiquitin/proteasome-independent manner. DISCUSSION: Zfra peptides exhibit a strong efficacy in blocking tau aggregation and amyloid Αß formation and restore memory deficits in 3×Tg mice, suggesting its potential for treatment of AD.

Hyaluronan activates Hyal-2/WWOX/Smad4 signaling and causes bubbling cell death when the signaling complex is overexpressed.

Malignant cancer cells frequently secrete significant amounts of transforming growth factor beta (TGF-ß), hyaluronan (HA) and hyaluronidases to facilitate metastasizing to target organs. In a non-canonical signaling, TGF-ß binds membrane hyaluronidase Hyal-2 for recruiting tumor suppressors WWOX and Smad4, and the resulting Hyal-2/WWOX/Smad4 complex is accumulated in the nucleus to enhance SMAD-promoter dependent transcriptional activity. Yeast two-hybrid analysis showed that WWOX acts as a bridge to bind both Hyal-2 and Smad4. When WWOX-expressing cells were stimulated with high molecular weight HA, an increased formation of endogenous Hyal-2/WWOX/Smad4 complex occurred rapidly, followed by relocating to the nuclei in 20-40 min. In WWOX-deficient cells, HA failed to induce Smad2/3/4 relocation to the nucleus. To prove the signaling event, we designed a real time tri-molecular FRET analysis and revealed that HA induces the signaling pathway from ectopic Smad4 to WWOX and finally to p53, as well as from Smad4 to Hyal-2 and then to WWOX. An increased binding of the Smad4/Hyal-2/WWOX complex occurs with time in the nucleus that leads to bubbling cell death. In contrast, HA increases the binding of Smad4/WWOX/p53, which causes membrane blebbing but without cell death. In traumatic brain injury-induced neuronal death, the Hyal-2/WWOX complex was accumulated in the apoptotic nuclei of neurons in the rat brains in 24 hr post injury, as determined by immunoelectron microscopy. Together, HA activates the Hyal-2/WWOX/Smad4 signaling and causes bubbling cell death when the signaling complex is overexpressed.

Zfra activates memory Hyal-2+ CD3- CD19- spleen cells to block cancer growth, stemness, and metastasis in vivo.

Zfra is a 31-amino-acid zinc finger-like protein, which participates in the tumor necrosis factor signaling. Here, we determined that when nude mice and BALB/c mice were pre-injected with nanogram levels of a synthetic Zfra1-31 or truncated Zfra4-10 peptide via tail veins, these mice became resistant to the growth, metastasis and stemness of melanoma cells, and many malignant cancer cells. The synthetic peptides underwent self-polymerization in phosphate-buffered saline. Alteration of the Ser8 phosphorylation site to Gly8 abolished Zfra aggregation and its-mediated cancer suppression in vivo. Injected Zfra peptide autofluoresced due to polymerization and was trapped mainly in the spleen. Transfer of Zfra-stimulated spleen cells to naïve mice conferred resistance to cancer growth. Zfra-binding cells, designated Hyal-2+ CD3- CD19- Z cells, are approximately 25-30% in the normal spleen, but are significantly downregulated (near 0-3%) in tumor-growing mice. Zfra prevented the loss of Z cells caused by tumors. In vitro stimulation or education of naïve spleen cells with Zfra allowed generation of activated Z cells to confer a memory anticancer response in naïve or cancer-growing mice. In particular, Z cells are abundant in nude and NOD-SCID mice, and can be readily activated by Zfra to mount against cancer growth.

Trafficking protein particle complex 6A delta (TRAPPC6AΔ) is an extracellular plaque-forming protein in the brain.

Tumor suppressor WWOX is involved in the progression of cancer and neurodegeneration. Here, we examined whether protein aggregation occurs in the brain of nondemented, middle-aged humans and whether this is associated with WWOX downregulation. We isolated an N-terminal internal deletion isoform, TPC6AΔ, derived from alternative splicing of the TRAPPC6A (TPC6A) gene transcript. TPC6AΔ proteins are present as aggregates or plaques in the extracellular matrix of the brain such as in the cortex. Filter retardation assays revealed that aggregate formation of TPC6AΔ occurs preceding Aß generation in the hippocampi of middle-aged postmortem normal humans. In a Wwox gene knockout mouse model, we showed the plaques of pT181-Tau and TPC6AΔ in the cortex and hippocampus in 3-week-old mice, suggesting a role of WWOX in limiting TPC6AΔ aggregation. To support this hypothesis, in vitro analysis revealed that TGF-ß1 induces dissociation of the ectopic complex of TPC6AΔ and WWOX in cells, and then TPC6AΔ undergoes Ser35 phosphorylation-dependent polymerization and induces caspase 3 activation and Aß production. Similarly, knockdown of WWOX by siRNA resulted in dramatic aggregation of TPC6AΔ. Together, when WWOX is downregulated, TPC6AΔ is phosphorylated at Ser35 and becomes aggregated for causing caspase activation that leads to Tau aggregation and Aß formation.

Identification of an In Vivo MEK/WOX1 Complex as a Master Switch for Apoptosis in T Cell Leukemia.

Not all leukemia T cells are susceptible to high levels of phorbol myristate acetate (PMA)-mediated apoptosis. At micromolar levels, PMA induces apoptosis of Jurkat T cells by causing mitochondrial polarization/de-polarization, release of cytosolic granules, and DNA fragmentation. Chemical inhibitors U0126 and PD98059 block mitogen-activated protein kinase kinase 1 (MEK1)-mediated phosphorylation of extracellular signal-regulated kinase (ERK) and prevent apoptosis. Mechanistically, proapoptotic tumor suppressor WOX1 (also named WWOX or FOR) physically interacts with MEK1, in part, in the lysosomes in Jurkat cells. PMA induces the dissociation, which leads to relocation of MEK1 to lipid rafts and WOX1 to the mitochondria for causing apoptosis. U0126 inhibits PMA-induced dissociation of WOX1/MEK1 complex and supports survival of Jurkat cells. In contrast, less differentiated Molt-4 T cells are resistant to PMA-induced dissociation of the WOX1/MEK1 complex and thereby are refractory to apoptosis. U0126 overturns the resistance for enhancing apoptosis in Molt-4 cells. Together, the in vivo MEK1/WOX1 complex is a master on/off switch for apoptosis in leukemia T cells.

Dramatic co-activation of WWOX/WOX1 with CREB and NF-kappaB in delayed loss of small dorsal root ganglion neurons upon sciatic nerve transection in rats.

BACKGROUND: Tumor suppressor WOX1 (also named WWOX or FOR) is known to participate in neuronal apoptosis in vivo. Here, we investigated the functional role of WOX1 and transcription factors in the delayed loss of axotomized neurons in dorsal root ganglia (DRG) in rats. METHODOLOGY/PRINCIPAL FINDINGS: Sciatic nerve transection in rats rapidly induced JNK1 activation and upregulation of mRNA and protein expression of WOX1 in the injured DRG neurons in 30 min. Accumulation of p-WOX1, p-JNK1, p-CREB, p-c-Jun, NF-kappaB and ATF3 in the nuclei of injured neurons took place within hours or the first week of injury. At the second month, dramatic nuclear accumulation of WOX1 with CREB (>65% neurons) and NF-kappaB (40-65%) occurred essentially in small DRG neurons, followed by apoptosis at later months. WOX1 physically interacted with CREB most strongly in the nuclei as determined by FRET analysis. Immunoelectron microscopy revealed the complex formation of p-WOX1 with p-CREB and p-c-Jun in vivo. WOX1 blocked the prosurvival CREB-, CRE-, and AP-1-mediated promoter activation in vitro. In contrast, WOX1 enhanced promoter activation governed by c-Jun, Elk-1 and NF-kappaB. WOX1 directly activated NF-kappaB-regulated promoter via its WW domains. Smad4 and p53 were not involved in the delayed loss of small DRG neurons. CONCLUSIONS/SIGNIFICANCE: Rapid activation of JNK1 and WOX1 during the acute phase of injury is critical in determining neuronal survival or death, as both proteins functionally antagonize. In the chronic phase, concurrent activation of WOX1, CREB, and NF-kappaB occurs in small neurons just prior to apoptosis. Likely in vivo interactions are: 1) WOX1 inhibits the neuroprotective CREB, which leads to eventual neuronal death, and 2) WOX1 enhances NF-kappaB promoter activation (which turns to be proapoptotic). Evidently, WOX1 is the potential target for drug intervention in mitigating symptoms associated with neuronal injury.

Complement C1q activates tumor suppressor WWOX to induce apoptosis in prostate cancer cells.

BACKGROUND: Tissue exudates contain low levels of serum complement proteins, and their regulatory effects on prostate cancer progression are largely unknown. We examined specific serum complement components in coordinating the activation of tumor suppressors p53 and WWOX (also named FOR or WOX1) and kinases ERK, JNK1 and STAT3 in human prostate DU145 cells. METHODOLOGY/PRINCIPAL FINDINGS: DU145 cells were cultured overnight in 1% normal human serum, or in human serum depleted of an indicated complement protein. Under complement C1q- or C6-free conditions, WOX1 and ERK were mainly present in the cytoplasm without phosphorylation, whereas phosphorylated JNK1 was greatly accumulated in the nuclei. Exogenous C1q rapidly restored the WOX1 activation (with Tyr33 phosphorylation) in less than 2 hr. Without serum complement C9, p53 became activated, and hyaluronan (HA) reversed the effect. Under C6-free conditions, HA induced activation of STAT3, an enhancer of metastasis. Notably, exogenous C1q significantly induced apoptosis of WOX1-overexpressing DU145 cells, but not vehicle-expressing cells. A dominant negative and Y33R mutant of WOX1 blocked the apoptotic effect. C1q did not enhance p53-mediated apoptosis. By total internal reflection fluorescence (TIRF) microscopy, it was determined that C1q destabilized adherence of WOX1-expressing DU145 cells by partial detaching and inducing formation of clustered microvilli for focal adhesion particularly in between cells. These cells then underwent shrinkage, membrane blebbing and death. Remarkably, as determined by immunostaining, benign prostatic hyperplasia and prostate cancer were shown to have a significantly reduced expression of tissue C1q, compared to age-matched normal prostate tissues. CONCLUSIONS/SIGNIFICANCE: We conclude that complement C1q may induce apoptosis of prostate cancer cells by activating WOX1 and destabilizing cell adhesion. Downregulation of C1q enhances prostate hyperplasia and cancerous formation due to failure of WOX1 activation.

Transforming growth factor beta1 signaling via interaction with cell surface Hyal-2 and recruitment of WWOX/WOX1.

Transforming growth factor beta (TGF-beta) initiates multiple signal pathways and activates many downstream kinases. Here, we determined that TGF-beta1 bound cell surface hyaluronidase Hyal-2 on microvilli in type II TGF-beta receptor-deficient HCT116 cells, as determined by immunoelectron microscopy. This binding resulted in recruitment of proapoptotic WOX1 (also named WWOX or FOR) and formation of Hyal-2.WOX1 complexes for relocation to the nuclei. TGF-beta1 strengthened the binding of the catalytic domain of Hyal-2 with the N-terminal Tyr-33-phosphorylated WW domain of WOX1, as determined by time lapse fluorescence resonance energy transfer analysis in live cells, co-immunoprecipitation, and yeast two-hybrid domain/domain mapping. In promoter activation assay, ectopic WOX1 or Hyal-2 alone increased the promoter activity driven by Smad. In combination, WOX1 and Hyal-2 dramatically enhanced the promoter activation (8-9-fold increases), which subsequently led to cell death (>95% of promoter-activated cells). TGF-beta1 supports L929 fibroblast growth. In contrast, transiently overexpressed WOX1 and Hyal-2 sensitized L929 to TGF-beta1-induced apoptosis. Together, TGF-beta1 invokes a novel signaling by engaging cell surface Hyal-2 and recruiting WOX1 for regulating the activation of Smad-driven promoter, thereby controlling cell growth and death.

Zfra is an inhibitor of Bcl-2 expression and cytochrome c release from the mitochondria.

Zfra is a small size 31-amino-acid C2H2 zinc finger-like protein, which is known to interact with c-Jun N-terminal kinase 1 (JNK1), WW domain-containing oxidoreductase (WWOX, FOR or WOX1), TNF receptor-associated death domain protein (TRADD) and nuclear factor kappaB (NF-kappaB) during stress response. Here, we show that Zfra became phosphorylated at Ser8 (as determined by specific antibody) and translocated to the mitochondria in response to inducers of mitochondrial permeability transition (MPT) (e.g. staurosporine and betulinic acid). Overexpressed Zfra induced cell death. This event is associated, in part, with increased dissipation of mitochondrial membrane potential (MMP) and increased chromosomal DNA fragmentation. Intriguingly, Zfra significantly downregulated Bcl-2 and yet blocked cytochrome c release from the mitochondria. Overexpression of an S8G-Zfra mutant (Ser8 to Gly8 alteration) could not induce cell death, probably due to its failure of translocating to the mitochondria and causing MMP dissipation. Over-expressed proapoptotic WOX1 induced cytochrome c release from the mitochondria. Zfra bound and blocked the effect of WOX1. Taken together, Ser8 is essential for overexpressed Zfra to exert cell death via the mitochondrial pathway. Zfra downregulates Bcl-2 and induces MMP dissipation but causes no cytochrome c release, indicating a novel death pathway from the mitochondria.

MPP+-induced neuronal death in rats involves tyrosine 33 phosphorylation of WW domain-containing oxidoreductase WOX1.

WW domain-containing oxidoreductase (named WWOX, FOR or WOX1) is a pro-apoptotic protein and tumor suppressor. Animals treated with dopaminergic neurotoxin 1-methyl-4-phenyl-pyridinium (MPP+) develop Parkinson's disease (PD)-like symptoms. Here we investigated whether WOX1 is involved in MPP+-induced neurodegeneration. Upon insult with MPP+ in rat brains, WOX1 protein was upregulated and phosphorylated at Tyr33 (or activated) in the injured neurons in the striatum and cortex ipsilaterally to intoxication, as determined by immunohistochemistry and Western blotting. Also, WOX1 was present in the condensed nuclei and damaged mitochondria of degenerative neurons, as revealed by transmission immunoelectron microscopy. Time-lapse microscopy revealed that MPP+ induced membrane blebbing and shrinkage of neuroblastoma SK-N-SH cells. Dominant-negative WOX1, a potent inhibitor of Tyr33 phosphorylation, abolished this event, indicating a critical role of the phosphorylation in apoptosis. c-Jun N-terminal kinase (JNK1) is known to bind and counteract the apoptotic function of WOX1. Suppression of JNK1 function by a dominant-negative spontaneously induced WOX1 activation. WOX1 physically interacted with JNK1 in SK-N-SH cells and rat brain extracts. MPP+ rapidly increased the binding, followed by dissociation, which is probably needed for WOX1 to exert apoptosis. We synthesized a short Tyr33-phosphorylated WOX1 peptide (11 amino acid residues). Interestingly, this peptide blocked MPP+-induced neuronal death in the rat brains, whereas non-phospho-WOX1 peptide had no effect. Together, activated WOX1 plays an essential role in the MPP+-induced neuronal death. Our synthetic phospho-WOX1 peptide prevents neuronal death, suggestive of its therapeutic potential in mitigating the symptoms of PD.