Null RPGRIP1 alleles in patients with Leber congenital amaurosis

We isolated and characterized the entire coding sequence of a human gene encoding a protein that interacts with RPGR, a protein that is absent or mutant in many cases of X-linked retinitis pigmentosa. The newly identified gene, called "RPGRIP1" for RPGR-interacting protein (MIM 605446), is located within 14q11, and it encodes a protein predicted to contain 1,259 amino acids. Previously published work showed that both proteins, RPGR and RPGRIP1, are present in the ciliary structure that connects the inner and outer segments of rod and cone photoreceptors. We surveyed 57 unrelated patients who had Leber congenital amaurosis for mutations in RPGRIP1 and found recessive mutations involving both RPGRIP1 alleles in 3 (6%) patients. The mutations all create premature termination codons and are likely to be null alleles. Patients with RPGRIP1 mutations have a degeneration of both rod and cone photoreceptors, and, early in life, they experience a severe loss of central acuity, which leads to nystagmus.     

Inhibition of cytokine-induced vascular cell adhesion molecule-1 expression; possible mechanism for anti-atherogenic effect of Agastache rugosa

Adhesion molecules such as vascular cell adhesion molecule-1 (VCAM-1) play an important role during the early stages of atherogenesis. Agastache rugosa has an anti-atherogenic effect in low density lipoprotein receptor -/- mice. Moreover, A. rugosa reduced macrophage infiltration and VCAM-1 expression has been localized in aortic endothelium that overlies early foam cell lesions. This study ascertained that tilianin (100 microM), a major component of A. rugosa, inhibits the tumor necrotic factor-alpha (TNF-alpha)-induced expression of VCAM-1 by 74% in cultured human umbilical vein endothelial cells (HUVECs). Also, tilianin (100 microM) reduced TNF-alpha-induced activation of nuclear factor-kappaB in HUVECs.     

Molecular consequences of activated microglia in the brain: overactivation induces apoptosis

Microglia, the resident immune cells in the brain, play a pivotal role in immune surveillance, host defense, and tissue repair in the CNS. In response to immunological challenges, microglia readily become activated as characterized by morphological changes, expression of surface antigens, and production of immune modulators that impact on neurons to induce neurodegeneration. However, little is known concerning the fate of activated microglia. In the present study, stimulation of cultured rat primary microglia with 1 ng/mL of the inflammagen lipopolysaccharide (LPS) resulted in a maximal activation as measured by the release of tumor necrosis factor alpha (TNF alpha). However, treatment with higher concentrations of LPS resulted in significantly lower quantities of detectable TNF alpha. Further analysis revealed that overactivation of microglia with higher concentrations of LPS (> 1 ng/mL) resulted in a time- and dose-dependent apoptotic death of microglia as defined by DNA strand breaks, surface expression of apoptosis-specific markers (phosphatidylserine), and activation of caspase-3. In contrast, astrocytes were insensitive to LPS-induced cytotoxicity. In light of the importance of microglia and the limited replenishment mechanism, depletion of microglia from the brain may severely hamper its capacity for combating inflammatory challenges and tissue repair. Furthermore, overactivation-induced apoptosis of microglia may be a fundamental self-regulatory mechanism devised to limit bystander killing of vulnerable neurons.     

Type D retrovirus Gag polyprotein interacts with the cytosolic chaperonin TRiC

The carboxy terminus-encoding portion of the gag gene of Mason-Pfizer monkey virus (M-PMV), the prototype immunosuppressive primate type D retrovirus, encodes a 36-amino-acid, proline-rich protein domain that, in the mature virion, becomes the p4 capsid protein. The p4 domain has no known role in M-PMV replication. We found that two mutants with premature termination codons that remove half or all of the p4 domain produced lower levels of stable Gag protein and of self-assembled capsids. Interestingly, yeast two-hybrid screening revealed that p4 specifically interacted with TCP-1gamma, a subunit of the chaperonin TRiC (TCP-1 ring complex). TRiC is a cytosolic chaperonin that is known to be involved in both folding and subunit assembly of a variety of cellular proteins. TCP-1gamma also associated with high specificity with the M-PMV pp24/16-p12 domain and human immunodeficiency virus p6. Moreover, in cells, Gag polyprotein associated with the TRiC chaperonin complex and this association depended on ATP hydrolysis. In the p4 truncation mutants, the Gag-TRiC association was significantly reduced. These results strongly suggest that cytosolic chaperonin TRiC is involved in Gag folding and/or capsid assembly. We propose that TRiC associates transiently with nascent M-PMV Gag molecules to assist in their folding. Consequently, properly folded Gag molecules carry out the intermolecular interactions involved in self-assembly of the immature capsid.     

Involvement of NADH/NADPH oxidase-derived superoxide in experimental vasospasm induced by periarterial blood in rat femoral artery

To elucidate the mechanism(s) involved in periarterial blood-mediated vasospasm in the rat femoral artery, vascular production of superoxide and related expression of intercellular adhesion molecule-1 (ICAM-1) were assessed with subsequent perivascular mobilization of granulocytes and macrophages. Arterial vasospasm characterized by increased wall thickness and decreased lumen size was observed on the side exposed to blood at 7 to 12 days, and these vascular changes were significantly ameliorated by pretreatment with NADH/NADPH oxidase inhibitor, diphenyleneiodonium (200 microM, locally). Increased mobilization of granulocytes was paralleled with the expression of ICAM-1 in the vessels at 24 hours after periarterial application of blood to the femoral artery, and then both declined. Subsequently, infiltration of macrophage progressively increased at all layers throughout 7 to 12 days. In in vitro study, a large amount of superoxide that was inhibitable by diphenyleneiodonium (20 and 100 microM) was produced at 3 hours upon application of 10% autologous blood to the aortic segments. Furthermore, ICAM-1 expression by autologous blood was well correlated with generation of superoxide anion in the aortic segment (r=0.975, P<0.05). Taken together, it is suggested that NADH/NADPH oxidase-derived superoxide is implicated in periarterial blood-induced vasospasm via increased expression of ICAM-1 with subsequent mobilization of granulocyte/macrophage.     

Cloning of the genomic sequence encoding a processed adenylate kinase 2 pseudogene

A chromosomal DNA sequence harboring a processed AK2B pseudogene was isolated from a human genomic library. It was a variant of the AK2B gene sequence including several point mutations, deletions, and insertions. The nucleotide sequence of the ORF of the AK2B pseudogene predicted a truncated form of the AK2B mutant suggesting that the processed pseudogene is nonfunctional. A repetitive sequence, AAAAGAGAG, found in the 5' and 3' flanking regions of the pseudogene and the poly(A) tract in the 3' end junction suggest that a mRNA of AK2B may have been converted to the processed pseudogene by retrotransposition events. Previously, it was suggested that an adenylate kinase (AK) 2 related gene on chromosome 2, confirmed by Southern analysis using somatic cell hybrid cell lines, may be a processed pseudogene. It is proposed that the processed pseudogene isolated in this study may be the AK2 related nonfunctional gene localized on human chromosomes 2.     

The inter-ligand Overhauser effect: A powerful new NMR approach for mapping structural relationships of macromolecular ligands

NMR experiments that transfer conformational information from the bound to the uncomplexed state via exchange have been utilized for many years. It is demonstrated here that inter-ligand NOEs (ILOEs), which exist in ternary complexes with enzymes or other macromolecular receptors, can be transferred via exchange to pairs of uncomplexed ligands. This approach is illustrated by studies of glycolate + NAD⁺ in the presence of porcine heart lactate dehydrogenase, and by glucose-6-phosphate + NADPH in the presence of L. mesenteroides glucose-6-phosphate dehydrogenase. This strategy opens up a general methodology for exploring the active sites of enzymes and for the development of artificial ligands which can function as inhibitors, or more generally as modifiers of protein function.     

Regio-selective preparation of vinyl adenosine ester catalyzed by alkaline protease

The transesterification of divinyladipate with adenosine in DMF containing 20% (v/v) DMSO was catalyzed by Streptomyces sp. alkaline protease and esterification occurred exclusively at the 3-position of hydroxyl group of ribofuranose in adenosine to give 3-O-vinyladipoyl adenosine without other products.     

Effects of epidermal growth factor on MDA-MB-468 breast cancer cells: alterations in polyamine biosynthesis and the expression of p21/CIP1/WAF1

We examined the effects of epidermal growth factor (EGF) on MDA-MB-468 cells to understand its mechanism of action in an EGF receptor-rich breast cancer cell line. EGF inhibited the growth of MDA-MB-468 cells with an IC50 of 1.5 +/- 0.5 nM, as determined by measurements of DNA content of cells in culture over a period of 4 to 6 days. This growth inhibition included apoptosis 24 h after EGF addition, as detected by an enzyme-linked immunosorbent assay (ELISA) and Hoechst 33342 staining. In EGF-treated cells, peak activities of two key enzymes of polyamine biosynthesis, ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC), were reduced by 57% and 83%, respectively. EGF treatment also caused a 30 to 50% decrease in cellular putrescine at all time points tested (12 to 48 h). EGF-induced inhibition of DNA synthesis was also partially reversed by the addition of putrescine or spermidine, but not by spermine. Western blot analysis of cell cycle regulatory proteins showed that EGF-mediated growth inhibition was associated with the induction of p21, an inhibitor of cyclin-dependent kinases. However, EGF had no significant effect on the expression of cyclin D1 or cyclin E. Furthermore, putrescine reversal of EGF effects was associated with the down-regulation of EGF-induced p21. These results suggest that the mechanism of growth inhibition by EGF in MDA-MB-468 cells include a down-regulation of polyamine biosynthesis and the induction of p21. Identification of growth regulatory pathways in breast cancer cells might be useful in the development of novel targets for therapeutic intervention.