No abstract

Myocardial infarction (MI) has been shown to induce endothelial dysfunction in peripheral resistance arteries and thus increase peripheral resistance. This study was designed to investigate the underlying mechanisms of post-MI-related dysfunctional dilatation of peripheral resistance arteries and, furthermore, to examine whether exercise may restore dysfunctional dilatation of peripheral resistance arteries. Adult male Sprague-Dawley rats were divided into three groups: sham-operated, MI, and MI + exercise. Ultrastructure and relaxation function of the mesenteric arteries, as well as phosphatidylinositol-3 kinase (PI3K), Akt kinases (Akt), endothelial nitric oxide synthase (eNOS) activity, and phosphorylation of PI3K, Akt, and eNOS by ACh were determined. Post-MI rats exhibited pronounced ultrastructural changes in mesenteric artery endothelial cells and endothelial dysfunction. In addition, the activities of PI3K, Akt, and eNOS, and their phosphorylation by ACh were significantly attenuated in mesenteric arteries (P < 0.05-0.01). After 8 wk of exercise, not only did endothelial cells appeared more normal in structure, but also ameliorated post-MI-associated mesenteric arterial dysfunction, which were accompanied by elevated activities of PI3K, Akt, and eNOS, and their phosphorylation by ACh (P < 0.05-0.01). Importantly, inhibition of either PI3K or eNOS attenuated exercise-induced restoration of the dilatation function and blocked PI3K, Akt, and eNOS phosphorylation by ACh in the mesenteric arteries. These data demonstrate that MI induces dysfunctional dilation of peripheral resistance arteries by degradation of endothelial structural integrity and attenuating PI3K-Akt-eNOS signaling. Exercise may restore dilatation function of peripheral resistance arteries by protecting endothelial structural integrity and increasing PI3K-Akt-eNOS signaling cascades.

Methanococcus jannaschii MJ0936 is a hypothetical protein of unknown function with over 50 homologs found in many bacteria and Archaea. To help define the molecular (biochemical and biophysical) function of MJ0936, we determined its crystal structure at 2.4-Å resolution and performed a series of biochemical screens for catalytic activity. The overall fold of this single domain protein consists of a four-layered structure formed by two ␤-sheets flanked by ␣-helices on both sides. The crystal structure suggested its biochemical function to be a nuclease, phosphatase, or nucleotidase, with a requirement for some metal ions. Crystallization in the presence of Ni 2؉ or Mn 2؉ produced a protein containing a binuclear metal center in the putative active site formed by a cluster of conserved residues. Analysis of MJ0936 against a panel of general enzymatic assays revealed catalytic activity toward bis-p-nitrophenyl phosphate, an indicator substrate for phosphodiesterases and nucleases. Significant activity was also found with two other phosphodiesterase substrates, thymidine 5 -monophosphate p-nitrophenyl ester and p-nitrophenylphosphorylcholine, but no activity was found for cAMP or cGMP. Phosphodiesterase activity of MJ0936 had an absolute requirement for divalent metal ions with Ni 2؉ and Mn 2؉ being most effective. Thus, our structural and enzymatic studies have identified the biochemical function of MJ0936 as that of a novel phosphodiesterase.Several hundred genomes have been sequenced so far, but no function can be inferred from the gene sequence of about half of the genes. Structural information may provide new clues as to the molecular (biochemical and biophysical) functions of the proteins coded by these genes of unknown functions.An open reading frame from Methanococcus jannaschii, MJ0936 (GI 1499771), is annotated as a conserved hypothetical protein in the PEDANT sequence data base (1). A PSI-PHI BLAST search found 56 bacterial or archaeal homologs with E value less than 0.003. Some of the homologs are annotated, and they can be grouped into three categories: (i) (conserved) hypothetical protein; (ii) VPS29-like (human vacuolar protein-sorting protein) phosphoesterase-related protein; (iii) predicted/ putative/probable phosphoesterase. Similarly, a Pfam (2) search suggests that this gene may belong to a protein family of calcineurin-like phosphoesterase. This Pfam protein family contains a large range of phosphoesterases, including protein phosphoserine phosphatases, nucleotidases, sphingomyelin phosphodiesterases, 2Ј,3Ј-cyclic AMP phosphodiesterases, and nucleases such as bacterial SbcD or yeast MRE11, as well as the VPS29-like phosphoesterase-related proteins mentioned above. Presumed metal-chelating residues are found to be conserved for the proteins of this family.To determine the function of MJ0936 and its homologues, we have solved the crystal structure of this protein and performed a series of biochemical screenings for catalytic activity. Through a combination of structural and enzymatic analyses, we ...

The formation of a fluid-filled cystic cavity after spinal cord injury (SCI) is a major obstacle for neural regeneration. In this study, the post-SCI cavity was bridged by a functional self-assembling peptide (F-SAP) nanofiber hydrogel coupled with growth factor “cocktail”. A sustained release of growth factors was achieved by carefully tailoring the physical hindrances and charge-induced interactions between the growth factors and the peptide nanofibers. Such an engineering microenvironment elicited axon regeneration, as determined by tracing of the descending pathway in the dorsal columns and immunochemical detection of regenerating axons beyond the lesion. Furthermore, the dynamic spatiotemporal activation line of endogenous NSCs (eNSCs) after severe SCI was thoroughly investigated. The results indicated that the growth factor-coupled F-SAP greatly facilitated eNSC proliferation, neuronal differentiation, maturation, myelination, and more importantly, the formation of interconnection with severed descending corticospinal tracts. The robust endogenous neurogenesis essentially led to the recovery of locomotion and electrophysiological properties. In conclusion, the growth factor-coupled F-SAP nanofiber hydrogel elucidated the therapeutic effect of eliciting endogenous neurogenesis by locally reassembling an extracellular matrix.