Molecular characterization of TRPA1 channel activation by cysteine-reactive inflammatory mediators

TRPA1 is a member of the transient receptor potential (TRP) cation channel family, and is predominantly expressed in nociceptive neurons of dorsal root ganglia (DRG) and trigeminal ganglia. Activation of TRPA1 by environmental irritants such as mustard oil, allicin and acrolein causes acute pain. However, the endogenous ligands that directly activate TRPA1 remain elusive in inflammation. Here, we show that a variety of inflammatory mediators (15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), nitric oxide (NO), hydrogen peroxide (H(2)O(2)), and proton (H(+))) activate human TRPA1 heterologously expressed in HEK cells. These inflammatory mediators induced robust Ca(2+) influx in a subset of mouse DRG neurons. The TRP channel blocker ruthenium red almost completely inhibited neuronal responses by 15d-PGJ(2) and NO, but partially suppressed responses to H(2)O(2) and H(+). Functional characterization of site-directed cysteine mutants of TRPA1 in combination with labeling experiments using biotinylated 15d-PGJ(2) demonstrated that modifications of cytoplasmic N-terminal cysteines (Cys421 and Cys621) were responsible for the activation of TRPA1 by 15d-PGJ(2). In TRPA1 responses to other cysteine-reactive inflammatory mediators, such as NO and H(2)O(2), the extent of impairment by respective cysteine mutations differed from those in TRPA1 responses to 15d-PGJ(2). Interestingly, the Cys421 mutation critically impaired the TRPA1 response to H(+) as well. Our findings suggest that TRPA1 channels are targeted by an array of inflammatory mediators to elicit inflammatory pain in the nervous system.     

Prostaglandin E2-activated Epac promotes neointimal formation of the rat ductus arteriosus by a process distinct from that of cAMP-dependent protein kinase A

We have demonstrated that chronic stimulation of the prostaglandin E2-cAMP-dependent protein kinase A (PKA) signal pathway plays a critical role in intimal cushion formation in perinatal ductus arteriosus (DA) through promoting synthesis of hyaluronan. We hypothesized that Epac, a newly identified effector of cAMP, may play a role in intimal cushion formation (ICF) in the DA distinct from that of PKA. In the present study, we found that the levels of Epac1 and Epac2 mRNAs were significantly up-regulated in the rat DA during the perinatal period. A specific EP4 agonist, ONO-AE1-329, increased Rap1 activity in the presence of a PKA inhibitor, PKI-(14-22)-amide, in DA smooth muscle cells. 8-pCPT-2'-O-Me-cAMP (O-Me-cAMP), a cAMP analog selective to Epac activator, promoted migration of DA smooth muscle cells (SMC) in a dose-dependent manner. Adenovirus-mediated Epac1 or Epac2 gene transfer further enhanced O-Me-cAMP-induced cell migration, although the effect of Epac1 overexpression on cell migration was stronger than that of Epac2. In addition, transfection of small interfering RNAs for Epac1, but not Epac2, significantly inhibited serum-mediated migration of DA SMCs. In the presence of O-Me-cAMP, actin stress fibers were well organized with enhanced focal adhesion, and cell shape was widely expanded. Adenovirus-mediated Epac1, but not Epac2 gene transfer, induced prominent ICF in the rat DA explants when compared with those with green fluorescent protein gene transfer. The thickness of intimal cushion became significantly greater (1.98-fold) in Epac1-overexpressed DA. O-Me-cAMP did not change hyaluronan production, although it decreased proliferation of DA SMCs. The present study demonstrated that Epac, especially Epac1, plays an important role in promoting SMC migration and thereby ICF in the rat DA.     

The chondroitin polymerase K4CP and the molecular mechanism of selective bindings of donor substrates to two active sites

Bacterial chondroitin polymerase K4CP is a multifunctional enzyme with two active sites. K4CP catalyzes alternative transfers of glucoronic acid (GlcA) and N-acetylgalactosamine (GalNAc) to elongate a chain consisting of the repeated disaccharide sequence GlcAbeta1-3GalNAcbeta1-4. Unlike the polymerization reactions of DNA and RNA and polypeptide synthesis, which depend upon templates, the monosaccharide polymerization by K4CP does not. To investigate the catalytic mechanism of this reaction, we have used isothermal titration calorimetry to determine the binding of the donor substrates UDP-GlcA and UDP-GalNAc to purified K4CP protein and its mutants. Only one donor molecule bound to one molecule of K4CP at a time. UDP-GlcA bound only to the C-terminal active site at a high affinity (K(d)=6.81 microm), thus initiating the polymerization reaction. UDP-GalNAc could bind to either the N-terminal or C-terminal active sites at a low affinity (K(d)=266-283 microm) but not to both sites at the same time. The binding affinity of UDP-GalNAc to a K4CP N-terminal fragment (residues 58-357) was profoundly decreased, yielding the average K(d) value of 23.77 microm, closer to the previously reported K(m) value for the UDP-GalNAc transfer reaction that takes place at the N-terminal active site. Thus, the first step of the reaction appears to be the binding of UDP-GlcA to the C-terminal active site, whereas the second step involves the C-terminal region of the K4CP molecule regulating the binding of UDP-GalNAc to only the N-terminal active site. Alternation of these two specific bindings advances the polymerization reaction by K4CP.     

Biofuel cell system employing thermostable glucose dehydrogenase

Enzyme biofuel cells utilizing glucose dehydrogenase as an anode enzyme were constructed. The glucose dehydrogenase is composed of a catalytic subunit, an electron transfer subunit, and a chaperon-like subunit. Cells, constructed using either a glucose dehydrogenase catalytic subunit or a glucose dehydrogenase complex, displayed power outputs that were dependent on the glucose concentration. The catalytic subunit in the anode maintained its catalytic activity for 24 h of operation. The biofuel cell which composed of glucose dehydrogenase complex functioned successfully even in the absence of an electron mediator at the anode cell. These results indicate the potential application of this thermostable glucose dehydrogenase for the construction of a compartment-less biofuel cell.     

Use of a recycle-type SEC method as a powerful tool for purification of thiosialoside derivatives

An efficient separation between fully acetylated thiosialoside methyl esters and fully acetylated Neu5Ac2en methyl esters was accomplished by means of a size-exclusion chromatography (SEC) method. Purity determinations and structural elucidation of the isolated compounds were performed by a combination of elemental analyses and spectroscopic analyses, including IR, ¹H, and ¹³C NMR, and mass spectroscopic analyses.     

Bone development in the jaw of Nile tilapia Oreochromis niloticus (Pisces: Cichlidae)

East African cichlids have evolved feeding apparatus morphologies adapted to their diverse feeding behaviors. The evolution of the oral jaw morphologies is accomplished by the diversity of bone formation during development. To further understand this evolutionary process, we examined the skeletal elements of the jaw and their temporal and sequential emergence, categorized by developmental stages, using the Nile tilapia Oreochromis niloticus as a model cichlid. We found that chondrogenesis started in Stage 17. The deposition of osteoid for the dermal bones commenced in Stage 18. The uptake of calcium dramatically shifted from the surface of larvae to the gills in Stage 20. The bone mineralization of the skeleton began in Stage 25. These data provide important information regarding the sequential events of craniofacial development in East African cichlids and lay the groundwork for studying the molecular mechanisms underlying adaptation of jaw structure to feeding behavior.     

Cyclooxygenase-2 induction by adiponectin is regulated by a sphingosine kinase-1 dependent mechanism in cardiac myocytes

The adipose-derived plasma protein, adiponectin (APN), has various protective effects on cardiovascular diseases. In this study, we show that endogenous APN is required for full cyclooxygenase-2 (COX-2) induction by ischemia-reperfusion injury in the heart in vivo. In rat neonatal cardiac myocytes, APN-induced COX-2 expression was reduced by treatment with a sphingosine kinase-1 (SphK-1) inhibitor or siRNA targeting SphK-1. Treatment with a sphingosine-1-phosphate (S1P) receptor antagonist also diminished COX-2 expression in response to APN stimulation. These findings suggest that APN is a physiological regulator of COX-2 signaling in the heart and that this regulation occurs in part via a SphK-1-S1P receptor dependent mechanism in cardiac myocytes.