Antisense peptide nucleic acid­peptide conjugates for functional analyses of genes in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is one of the most common and clinically important pathogens because of its resistance to a wide variety of antibiotics. A number of treatments of P. aeruginosa have been developed, but there is still no definitive one. Antisense drugs have a great potential to treat multidrug-resistant P. aeruginosa because this technology, in principle, can inhibit the expression of any essential genes. Nucleic Acid Ther.2012, 22, 323 reported that peptide nucleic acid (PNA) antisenses conjugated to the carrier peptide (RXR)4 and targeted to ftsZ and acpP (essential genes) had antibacterial activity in P. aeruginosa. However, growth inhibition was also found with peptide-PNA antisense conjugates of mismatched sequences (negative controls), and hence there remains a possibility for considerable enhancement of basal level activity due to the general toxicity. To assess the true potential of peptide-PNA conjugates, we measured sequence-dependent knockdown of the (RXR)4-PNA conjugates by using a scrambled sequence as a negative control. In addition, we evaluated (RXR)4-PNA antisenses against three other essential genes (lepB, lptD and mraY) and a non-essential gene (PA1303), and confirmed that multiple sequences targeting only the essential genes showed antimicrobial activity in P. aeruginosa PAO1 cells. We also conducted a rescue experiment and confirmed that the antimicrobial activity of anti-mraY antisenses was an on-target effect, not due to general toxicity. These findings indicate that the (RXR)4­PNA antisense should be a useful tool for target validation of a specific gene and could be a therapeutic platform capable of targeting a variety of genes in P. aeruginosa.

Vesnarinone suppresses TNFα mRNA expression by inhibiting valosin-containing protein.

Vesnarinone is a synthetic quinolinone derivative used in the treatment of cardiac failure and cancer. It is also known to cause agranulocytosis as a side effect, which restricts its use, although the mechanism underlying agranulocytosis is not well understood. Here, we show that vesnarinone binds to valosin-containing protein (VCP), which interacts with polyubiquitinated proteins and is essential for the degradation of IκBα to activate nuclear factor (NF)κB. We show that vesnarinone impairs the degradation of IκBα, and that the impairment of the degradation of IκBα is the result of the inhibition of the interaction between VCP and the 26S proteasome by vesnarinone. These results suggest that vesnarinone suppresses NFκB activation by inhibiting the VCP-dependent degradation of polyubiquitinated IκBα, resulting in the suppression of tumor necrosis factor-α mRNA expression.

Vitamin K2 covalently binds to Bak and induces Bak-mediated apoptosis.

Vitamin K2 (VK2, menaquinone) is known to have anticancer activity in vitro and in vivo. Although its effect is thought to be mediated, at least in part, by the induction of apoptosis, the underlying molecular mechanism remains elusive. Here, we identified Bcl-2 antagonist killer 1 (Bak) as a molecular target of VK2-induced apoptosis. VK2 directly interacts with Bak and induces mitochondrial-mediated apoptosis. Although Bak and Bcl-2-associated X protein (Bax), another member of the Bcl-2 family, are generally thought to be functionally redundant, only Bak is necessary and sufficient for VK2-induced cytochrome c (cyt c) release and cell death. Moreover, VK2-2,3 epoxide, an intracellular metabolite of VK2, was shown to covalently bind to the cysteine-166 residue of Bak. Several lines of evidence suggested that the covalent attachment of VK2 is critical for apoptosis induction. Thus this study reveals a specific role for Bak in mitochondria-mediated apoptosis. This study also provides insight into the anticancer effects of VK2 and suggests that Bak may be a potential target of cancer therapy.

High-performance affinity purification for identification of 15-deoxy-Δ 12,14 -PGJ2 interacting factors using magnetic nanobeads.

Prostaglandin J2 (PGJ2) family have been reported to show various kinds of biological activities. Considerable progress has been made toward understanding the mechanism of adipogenesis, however, the mechanisms of other actions of PGJ2 family remain controversial. The 15-deoxy-Δ(12,14) -PGJ2 (15d-PGJ2) is one of the members of PGJ2 family, and is known as a ligand for peroxisome proliferator-activated receptor γ (PPARγ), which promotes the expression of the crucial genes for adipogenesis. In this study, we found that 15d-PGJ2 did not stimulate PPARγ-mediated gene expression in HEK293 cells whereas 15d-PGJ2 transactivated PPARγ-dependent transcription in other cell lines. Moreover, we confirmed that 15d-PGJ2 suppressed the growth of HEK293 cells. These observations suggest that 15d-PGJ2 shows another biological activity e.g. growth inhibition in HEK293 cells via unknown receptor for 15d-PGJ2. The aim of this study is to develop and validate effective purification system for PGJ2 interacting factors (PGJIFs). We have recently developed high performance magnetic nanobeads. In this study, we have newly developed 15d-PGJ2-immobilized beads by conjugating 15d-PGJ2 to the surface of these nanobeads. Firstly, we showed that PPARγ specifically bound to 15d-PGJ2-immobilized beads. Secondly, we newly identified voltage dependent anionic channel 1 (VDAC1) as new PGJIF from crude extracts of HEK293 cells using this affinity purification system. These data presented here demonstrate that 15d-PGJ2-immobilized beads are effective tool for purification of PGJIFs directly from crude cell extracts.

Exogenous coproporphyrin III production by Corynebacterium aurimucosum and Microbacterium oxydans in erythrasma lesions.

Erythrasma is a superficial skin disease caused by Gram-positive Corynebacterium species. Coral-red fluorescence under Wood's light, strongly suggestive of erythrasma, can be attributed to the presence of porphyrins. Fractionated porphyrin analysis in erythrasma lesions is yet to be reported. We attempted to investigate erythrasma lesions by isolating the responsible bacteria and determining their exogenous porphyrin production by HPLC analysis. We observed a 78-year-old woman with erythrasma who had a well-demarcated slightly scaling patch on her left foot, between the fourth and fifth toes. Two kinds of colonies on 5 % sheep blood agar were obtained from this lesion. Analysis of the 16S rRNA sequence revealed the colonies to be Corynebacterium aurimucosum and Microbacterium oxydans. HPLC analysis demonstrated that coproporphyrin III (Copro III) levels were clearly elevated, although the amounts of protoporphyrin were diminished. These results indicate that the fluorescent substance was Copro III. This study supports the view that excess Copro III synthesis by C. aurimucosum and M. oxydans leads to accumulation of porphyrin in cutaneous tissue, which emits a coral-red fluorescence when exposed to Wood's light.

Capsaicin binds to prohibitin 2 and displaces it from the mitochondria to the nucleus.

Capsaicin is widely used as a food additive and as an analgesic agent. Besides its well-known role in nociception, which is mediated by vanilloid receptor 1 specifically expressed in dorsal root ganglion neurons, capsaicin has also been considered as a potential anticancer agent, as it inhibits cell proliferation and induces apoptosis in various types of cancer cells. Here we identified a new molecular target of capsaicin from human myeloid leukemia cells. We show that capsaicin binds to prohibitin (PHB) 2, which is normally localized to the inner mitochondrial membrane, and induces its translocation to the nucleus. PHB2 is implicated in the maintenance of mitochondrial morphology and the control of apoptosis. We also provide evidence suggesting that capsaicin causes apoptosis directly through the mitochondria and that PHB2 contributes to capsaicin-induced apoptosis at multiple levels. This work will serve as an important foundation for further understanding of anticancer activity of capsaicin.

Adenine nucleotide translocator transports haem precursors into mitochondria.

Haem is a prosthetic group for haem proteins, which play an essential role in oxygen transport, respiration, signal transduction, and detoxification. In haem biosynthesis, the haem precursor protoporphyrin IX (PP IX) must be accumulated into the mitochondrial matrix across the inner membrane, but its mechanism is largely unclear. Here we show that adenine nucleotide translocator (ANT), the inner membrane transporter, contributes to haem biosynthesis by facilitating mitochondrial accumulation of its precursors. We identified that haem and PP IX specifically bind to ANT. Mitochondrial uptake of PP IX was inhibited by ADP, a known substrate of ANT. Conversely, ADP uptake into mitochondria was competitively inhibited by haem and its precursors, suggesting that haem-related porphyrins are accumulated into mitochondria via ANT. Furthermore, disruption of the ANT genes in yeast resulted in a reduction of haem biosynthesis by blocking the translocation of haem precursors into the matrix. Our results represent a new model that ANT plays a crucial role in haem biosynthesis by facilitating accumulation of its precursors into the mitochondrial matrix.

The enteropathogenic E. coli effector EspB facilitates microvillus effacing and antiphagocytosis by inhibiting myosin function.

Enteropathogenic Escherichia coli (EPEC) destroys intestinal microvilli and suppresses phagocytosis by injecting effectors into infected cells through a type III secretion system (TTSS). EspB, a component of the TTSS, is also injected into the cytoplasm of host cells. However, the physiological functions of EspB within the host cell cytoplasm remain unclear. We show that EspB binds to myosins, which are a superfamily of proteins that interact with actin filaments and mediate essential cellular processes, including microvillus formation and phagocytosis. EspB inhibits the interaction of myosins with actin, and an EspB mutant that lacks the myosin-binding region maintained its TTSS function but could not induce microvillus effacing or suppress phagocytosis. Moreover, the myosin-binding region of EspB is essential for Citrobacter rodentium, an EPEC-related murine pathogen, to efficiently infect mice. These results suggest that EspB inhibits myosin functions and thereby facilitates efficient infection by EPEC.

Porphyrin accumulation in mitochondria is mediated by 2-oxoglutarate carrier.

Heme (Fe-protoporphyrin IX), an endogenous porphyrin derivative, is an essential molecule in living aerobic organisms and plays a role in a variety of physiological processes such as oxygen transport, respiration, and signal transduction. For the biosynthesis of heme or the mitochondrial heme proteins, heme or its biosynthetic precursor porphyrin must be transported into mitochondria from cytosol. The mechanism of porphyrin accumulation in the mitochondrial inner membrane is unclear. In the present study, we analyzed the mechanism of mitochondrial translocation of porphyrin derivatives. We showed that palladium meso-tetra(4-carboxyphenyl)porphyrin (PdTCPP), a phosphorescent porphyrin derivative, accumulated in the mitochondria of several cell lines. Using affinity latex beads, we showed that 2-oxoglutarate carrier (OGC), the mitochondrial transporter of 2-oxoglutarate, bound to PdTCPP, and in vitro PdTCPP inhibited 2-oxoglutarate uptake into mitochondria in a competitive manner (Ki = 15 microM). Interestingly, all types of porphyrin derivatives examined in this study competitively inhibited 2-oxoglutarate uptake into mitochondria, including protoporphyrin IX, coproporphyrin III, and hemin. Furthermore, mitochondrial accumulation of porphyrins was inhibited by 2-oxoglutarate or OGC inhibitor. These results suggested that porphyrin accumulation in mitochondria is mediated by OGC and that porphyrins are able to competitively inhibit 2-oxoglutarate uptake into mitochondria. This is the first report of a putative mechanism for accumulation of porphyrins in the mitochondrial inner membrane.

TFII-I down-regulates a subset of estrogen-responsive genes through its interaction with an initiator element and estrogen receptor alpha.

TFII-I was initially identified as the general transcription factor that binds to initiator (Inr) elements in vitro. Subsequent studies have shown that TFII-I activates transcription of various genes either through Inr elements or through other upstream elements in vivo. Since, however, most studies so far on TFII-I have been limited to over-expression and reporter gene assays, we reevaluated the role of TFII-I in vivo by using stable knockdown with siRNA and by examining the expression of endogenous genes. Contrary to the widely accepted view, here we show that TFII-I is not important for cell viability in general but rather inhibits the growth of MCF-7 human breast cancer cells. MCF-7 cells are known to proliferate in an estrogen-dependent manner. Through analysis of TFII-I's cell-type specific growth inhibitory effect, we show evidence that TFII-I down-regulates a subset of estrogen-responsive genes, only those containing Inr elements, by recruiting estrogen receptor (ER) alpha and corepressors to these promoters. Thus, this study has revealed an unexpected new role of TFII-I as a negative regulator of transcription and cell proliferation.