TMPRSS4 is a novel type II transmembrane serine protease found at the cell surface that is highly expressed in pancreatic, colon and gastric cancer tissues. However, the biological functions of TMPRSS4 in cancer are unknown. Here we show, using reverse transcription-PCR, that TMPRSS4 is highly elevated in lung cancer tissues compared with normal tissues and is also broadly expressed in a variety of human cancer cell lines. Knockdown of TMPRSS4 by small interfering RNA treatment in lung and colon cancer cell lines was associated with reduction of cell invasion and cell-matrix adhesion as well as modulation of cell proliferation. Conversely, the invasiveness, motility and adhesiveness of SW480 colon carcinoma cells were significantly enhanced by TMPRSS4 overexpression. Furthermore, overexpression of TMPRSS4 induced loss of E-cadherin-mediated cell-cell adhesion, concomitant with the induction of SIP1/ZEB2, an Ecadherin transcriptional repressor, and led to epithelialmesenchymal transition events, including morphological changes, actin reorganization and upregulation of mesenchymal markers. TMPRSS4-overexpressing cells also displayed markedly increased metastasis to the liver in nude mice upon intrasplenic injection. Taken together, these studies suggest that TMPRSS4 controls the invasive and metastatic potential of human cancer cells by facilitating an epithelial-mesenchymal transition; TMPRSS4 may be a potential therapeutic target for cancer treatment.

Oxytricha nova telomeric DNA contains guanine-rich short-tandem repeat sequences (GGGGTTTT) n and terminates as a single strand at the 3'-end. This single-stranded overhang forms a novel DNA structure, namely, G-quadruplex, comprising four quartets. In this study, we investigated the structures and dynamics of unimolecular Oxytricha nova ( O. nova) telomeric G-quadruplexes by performing single molecule fluorescence resonance energy transfer (FRET) spectroscopy and bulk circular dichroism (CD) measurements. We observed that unimolecular O. nova G-quadruplexes exhibit structural polymorphism according to monovalent cations. In the presence of Na (+), only antiparallel conformation is detected, which was demonstrated in previous studies; however, in the presence of K (+), they fold into two different conformations, a parallel conformation and an antiparallel one different from that induced by Na (+). Furthermore, these G-quadruplexes show extremely high stability in their dynamics when compared with human G-quadruplexes. While human telomeric G-quadruplexes that possess three quartets display fast dynamic behavior (<100 s) at low K (+) concentrations or high temperatures, O. nova G-quadruplexes maintain their conformational state for a long time (>1000 s), even at the lowest K (+) concentration and the highest temperature investigated. This high stability is primarily due to an extra quartet that results in additional cation coordination. In addition to cation coordination, we propose that other factors such as base stacking and the size of the thymine loop may contribute to the stability of O. nova G-quadruplexes; this is based on the fact that the O. nova G-quadruplexes were observed to be more stable than the human ones in the presence of Li (+), which is known to greatly destabilize G-quadruplexes because of imprecise coordination. This extreme stability of four-quartet G-quadruplexes enables telomere protection even in the absence of protective proteins or in the case of abrupt environmental changes, although only a single G-quadruplex structure can be derived from the short single-stranded overhang.

Human phosphoserine phosphatase (HPSP) regulates the levels of glycine and D-serine, the putative co-agonists for the glycine site of the NMDA receptor in the brain. Here, we describe the first crystal structures of the HPSP in complexes with the competitive inhibitor 2-amino-3-phosphonopropionic acid (AP3) at 2.5 Å, and the phosphate ion (Pi) and the product uncompetitive inhibitor L-serine (HPSP⅐L-Ser⅐Pi) at 2.8 Å. The complex structures reveal that the open-closed environmental change of the active site, generated by local rearrangement of the ␣-helical bundle domain, is important to substrate recognition and hydrolysis. The maximal extent of this structural rearrangement is shown to be about 13 Å at the L4 loop and about 25°at the helix ␣3. Both the structural change and mutagenesis data suggest that Arg-65 and Glu-29 play an important role in the binding of the substrate. Interestingly, the AP3 binding mode turns out to be significantly different from that of the natural substrate, phospho-L-serine, and the HPSP⅐L-Ser⅐Pi structure provides a structural basis for the feedback control mechanism of serine. These analyses allow us to provide a clear model for the mechanism of HPSP and a framework for structure-based drug development. Phosphoserine phosphatase (PSP)1 is an important enzyme in the phosphorylated pathway of serine biosynthesis, which contributes a major portion of the endogenous L-serine (1, 2). In the mammalian nervous system, D-serine is converted from L-serine by serine racemase (3, 4) and acts as a co-agonist of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors, a major neurotransmitter receptor family (5). NMDA receptors require coactivation at a glycine site where D-serine, present in high levels in the mammalian brain, is three times more potent than glycine (6). Recently, a subset of NMDA receptors has been found to be activated by glycine or D-serine in the absence of glutamate (7). The enzymatic reaction of PSP is Mg 2ϩ -dependent and results in the dephosphorylation of phospho-Lserine with the formation of a phosphoenzyme intermediate, which is subsequently autodephosphorylated. The resulting product, L-serine, is not only a precursor for the biosynthesis of glycine but also an uncompetitive inhibitor for the enzymatic reaction of PSP (8). It may be possible to regulate NMDA activity by using selective inhibitors against serine racemase and/or PSP.The PSP family and P-type ATPases are members of the haloacid dehalogenase-like hydrolase family (9 -11). The crystal structures have been elucidated for several members of the haloacid dehalogenase superfamily: the L-2-haloacid dehalogenases, CheY, P-type ATPase and, recently, Methanococcus jannaschii (MJ) PSP (12-16). Three conserved motifs have been observed in amino acid sequences in members of the haloacid dehalogenase superfamily, and these residues are located in the active pocket. The significance of these motifs was confirmed by an assay of mutants for substrate hydrolysis (17). Other phosphoesters, including phosphothreo...

Background Transmembrane serine protease 4 (TMPRSS4) is a cell surface–anchored serine protease. Elevated expression of TMPRSS4 correlates with poor prognosis in colorectal cancer, gastric cancer, prostate cancer, non–small cell lung cancer, and other cancers. Previously, we demonstrated that TMPRSS4 promotes invasion and proliferation of prostate cancer cells. Here, we investigated whether TMPRSS4 confers cancer stem–like properties to prostate cancer cells and characterized the underlying mechanisms. Methods Acquisition of cancer stem–like properties by TMPRSS4 was examined by monitoring anchorage-independent growth, tumorsphere formation, aldehyde dehydrogenase (ALDH) activation, and resistance to anoikis and drugs in vitro and in an early metastasis model in vivo. The underlying molecular mechanisms were evaluated, focusing on stemness-related factors regulated by epithelial–mesenchymal transition (EMT)-inducing transcription factors. Clinical expression and significance of TMPRSS4 and stemness-associated factors were explored by analyzing datasets from The Cancer Genome Atlas (TCGA). Results TMPRSS4 promoted anchorage-independent growth, ALDH activation, tumorsphere formation, and therapeutic resistance of prostate cancer cells. In addition, TMPRSS4 promoted resistance to anoikis, thereby increasing survival of circulating tumor cells and promoting early metastasis. These features were accompanied by upregulation of stemness-related factors such as SOX2, BMI1, and CD133. SLUG and TWIST1, master EMT-inducing transcription factors, made essential contributions to TMPRSS4-mediated cancer stem cell (CSC) features through upregulation of SOX2. SLUG stabilized SOX2 via preventing proteasomal degradation through its interaction with SOX2, while TWIST1 upregulated transcription of SOX2 by interacting with the proximal E-box element in the SOX2 promoter. Clinical data showed that TMPRSS4 expression correlated with the levels of SOX2, PROM1, SNAI2, and TWIST1. Expression of SOX2 was positively correlated with that of TWIST1, but not with other EMT-inducing transcription factors, in various cancer cell lines. Conclusions Together, these findings suggest that TMPRSS4 promotes CSC features in prostate cancer through upregulation of the SLUG- and TWIST1-induced stem cell factor SOX2 beyond EMT. Thus, TMPRSS4/SLUG–TWIST1/SOX2 axis may represent a novel mechanism involved in the control of tumor progression.