Hyaluronidases and hyaluronan are important mediators of tissue remodeling and cancer cell metastasis. Metastatic and malignant breast and prostate cancers frequently overexpress hyaluronidases and hyaluronan (1, 2). Hyaluronidases PH-20, Hyal-1, and Hyal-2 are known to induce the expression of a candidate tumor suppressor WW domaincontaining oxidoreductase WOX1 (also known as WWOX, FOR, or WWOXv1) (3-5).The human WWOX gene, which comprises nine exons encoding the WWOX/WOX1 family proteins, is located on a fragile site on the chromosome ch16q23.3-24.1 (6 -9). Eight mRNA transcripts of the WWOX gene have been found so far (7). However, it is still not known whether all of the mRNA transcripts are translated successfully into proteins. Isoforms WWOXv1 (46 kDa), WWOXv2 (42 kDa), and WWOXv8 (60 kDa) and several other small proteins can be found in normal and several types of cancer cells (3, 8 -11). 3 Genetic alterations of the WWOX gene and disappearance of WWOX/WOX1 family proteins have been shown in multiple types of cancers, especially at an invasive or a metastatic stage (8,9,(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Hypermethylation of the WWOX gene may inactivate its expression (21). In contrast, significant up-regulation of WWOX/WOX1 family proteins has been shown during progression of breast, prostate and other cancers to a premetastatic state (10,22,23). Also, absent expression of these family proteins in metastatic cancer cells is not necessarily due to disruption of the WWOX gene. We have recently determined that post-transcriptional blockade of the fulllength mRNA translation to protein may account for the disappearance of the WWOX/WOX1 family proteins in cutaneous squamous cell carcinoma cells in patients and in UVB-treated mice (24).Wild type WOX1 possesses two N-terminal WW domains (containing conserved tryptophan residues), a nuclear localization sequence and a C-terminal short-chain alcohol dehydrogenase/reductase domain (which contains a mitochondria-targeting sequence) (3). Sex steroid hormones such as estrogen and androgen activate WOX1 via Tyr 33 phosphorylation (p-WOX1) and nuclear translocation (11). Importantly, p-WOX1 is located in the mitochondria during benign prostatic hypertrophy (11). Nuclear translocation of p-WOX1 occurs when prostate cells progress toward cancerous and metastatic states (11), suggesting a critical role of WOX1 phosphorylation during prostate cancer development.We determined that WOX1 enhances the cytotoxic function of tumor necrosis factor (TNF) 4 and induces apoptosis when overexpressed (3). We also showed that in response to stress or apoptotic stimuli, WOX1 becomes phosphorylated at Tyr 33 , which allows its complex formation with activated p53 and JNK1 (25). The p53-WOX1 complex translocates to the mitochondria and nuclei to mediate apoptosis (25,26). WOX1 induces apoptosis synergistically with p53 (3,25). In contrast, JNK1 may block WOX1-induced cell death (25). Src is known to phosphorylate WOX1 at Tyr 33 (27). We also determined that Tyr 33 -phosphorylated WO...
Transforming growth factor  (TGF-) initiates multiple signal pathways and activates many downstream kinases. Here, we determined that TGF-1 bound cell surface hyaluronidase Hyal-2 on microvilli in type II TGF- 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-2⅐WOX1 complexes for relocation to the nuclei. TGF-1 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 twohybrid 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-1 supports L929 fibroblast growth. In contrast, transiently overexpressed WOX1 and Hyal-2 sensitized L929 to TGF-1-induced apoptosis. Together, TGF-1 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. Transforming growth factor  (TGF-)4 plays a dual role in cell growth and tumorigenesis (1, 2). TGF- inhibits mammary epithelial cell growth. In contrast, invasive cancer cells frequently overproduce TGF- to promote growth and metastasis (1, 2). The underlying mechanism is largely unknown. TGF- induces the development of metastatic phenotypes, i.e. stimulation of epithelial-mesenchymal transitions in cancerous mammary epithelial cells (1, 2). These cells are normally devoid of functional type II TGF- receptor (TRII), suggesting that TGF- binds to an alternative receptor for signaling.Hyaluronan is the major components of pericellular coat and plays a key role in affecting cell morphology, communication, and behavior (3-5). Up-regulation of hyaluronan and hyaluronidases Hyal-1, Hyal-2, and PH-20 is associated with cancer metastasis (3-5). Hyaluronidases counteract the activity of TGF-1 (6 -8). TGF-1 suppresses the proliferation of normal epithelial cells, whereas PH-20 blocks the TGF-1 effect (6). Hyal-1 and Hyal-2 enhance the cytotoxic function of TNF and block TGF-1-mediated protection of murine L929 fibroblasts from TNF cytotoxicity (6 -8).Hyaluronidases PH-20, Hyal-1, and Hyal-2 induce the expression of tumor suppressor WW domain-containing oxidoreductase, known as WWOX, FOR or WOX1 (8 -11). Human WWOX gene is located on a chromosomal fragile site 16q23 and encodes WWOX/FOR/WOX1 and isoforms (9, 10, 12-16). The full-length 46-kDa WOX1 possesses two N-terminal WW domains (containing conserved tryptophan residues), a nuclear localization sequence between the WW domains, and a C-terminal short chain alcohol dehydrogenase/reductase domain. Numerous exogenous stimuli, including sex stero...
The role of a small transforming growth factor beta (TGF-β)-induced TIAF1 (TGF-β1-induced antiapoptotic factor) in the pathogenesis of Alzheimer's disease (AD) was investigated. TIAF1 physically interacts with mothers against DPP homolog 4 (Smad4), and blocks SMAD-dependent promoter activation when overexpressed. Accordingly, knockdown of TIAF1 by small interfering RNA resulted in spontaneous accumulation of Smad proteins in the nucleus and activation of the promoter governed by the SMAD complex. TGF-β1 and environmental stress (e.g., alterations in pericellular environment) may induce TIAF1 self-aggregation in a type II TGF-β receptor-independent manner in cells, and Smad4 interrupts the aggregation. Aggregated TIAF1 induces apoptosis in a caspase-dependent manner. By filter retardation assay, TIAF1 aggregates were found in the hippocampi of nondemented humans and AD patients. Total TIAF1-positive samples containing amyloid β (Aβ) aggregates are 17 and 48%, respectively, in the nondemented and AD groups, suggesting that TIAF1 aggregation occurs preceding formation of Aβ. To test this hypothesis, in vitro analysis showed that TGF-β-regulated TIAF1 aggregation leads to dephosphorylation of amyloid precursor protein (APP) at Thr668, followed by degradation and generation of APP intracellular domain (AICD), Aβ and amyloid fibrils. Polymerized TIAF1 physically interacts with amyloid fibrils, which would favorably support plaque formation in vivo.
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