Prostaglandin E2 regulates melanocyte dendrite formation through activation of PKCzeta

Prostaglandins are lipid signaling intermediates released by keratinocytes in response to ultraviolet irradiation (UVR) in the skin. The main prostaglandin released following UVR is PGE(2), a ligand for 4 related G-protein-coupled receptors (EP(1), EP(2), EP(3) and EP(4)). Our previous work established that PGE(2) stimulates melanocyte dendrite formation through activation of the EP(1) and EP(3) receptors. The purpose of the present report is to define the signaling intermediates involved in EP(1)- and EP(3)-dependent dendrite formation in human melanocytes. We recently showed that activation of the atypical PKCzeta isoform stimulates melanocyte dendricity in response to treatment with lysophosphatidylcholine. We therefore examined the potential contribution of PKCzeta activation on EP(1)- and EP(3)-dependent dendrite formation in melanocytes. Stimulation of the EP(1) and EP(3) receptors by selective agonists activated PKCzeta, and inhibition of PKCzeta activation abrogated EP(1)- and EP(3)-receptor-mediated melanocyte dendricity. Because of the importance of Rho-GTP binding proteins in the regulation of melanocyte dendricity, we also examined the effect of EP(1) and EP(3) receptor activation on Rac and Rho activity. Neither Rac nor Rho was activated upon treatment with EP(1,3)-receptor agonists. We show that melanocytes express only the EP(3A1) isoform, but not the EP(3B) receptor isoform, previously associated with Rho activation, consistent with a lack of Rho stimulation by EP(3) agonists. Our data suggest that PKCzeta activation plays a predominant role in regulation of PGE(2)-dependent melanocyte dendricity.     

Apolipoprotein E4 in macrophages enhances atherogenesis in a low density lipoprotein receptor-dependent manner

Apolipoprotein E (apoE) and the low density lipoprotein receptor (LDLr) are well recognized determinants of atherosclerosis. In addition to hepatocytes, where both are highly expressed and contribute to plasma lipoprotein clearance, they are expressed in vascular cells and macrophages. In this study, we examined the effects of human apoE isoforms and LDLr levels in atherogenic pathways in primary macrophages ex vivo and atherosclerosis development after bone marrow transfer in vivo using mice expressing human apoE isoforms and different levels of LDLr expression. Increases in LDLr expression significantly increased cholesterol delivery into macrophages in culture, and the effects were more prominent with lipoproteins containing apoE4 than those containing apoE3. Conversely, increased LDLr expression reduced cholesterol efflux in macrophages expressing apoE4 but not in macrophages expressing apoE3. Furthermore, apoE3 protected VLDL from oxidation in vitro more than did apoE4. In LDLr-deficient mice expressing the human apoE4 isoform, Apoe4/4 Ldlr-/-, the replacement of bone marrow cells with those expressing LDLr increased atherosclerotic lesions in a dose-dependent manner compared with mice transplanted with cells having no LDLr. In contrast, atherosclerosis in Apoe3/3 Ldlr-/- mice, expressing the human apoE3 isoform, did not differ by the levels of macrophage LDLr expression. Our results demonstrate that apoE4, but not apoE3, in macrophages enhances atherosclerotic plaque development in mice in an LDLr-dependent manner and suggests that this interaction may contribute to the association of apoE4 with an increased cardiovascular risk in humans.     

Longitudinal glia in the fly CNS: pushing the envelope on glial diversity and neuron-glial interactions

Interactions between neurons and glial cells are crucial for nervous system development and function in all complex organisms, and many functional, morphological and molecular features of glia are well conserved among species. Here we review studies of the longitudinal glia (LG) in the Drosophila CNS. The LG envelop the neuropil in a membrane sheath, and have features resembling both oligodendrocytes and astrocytes. Because of their unique lineage, morphology and molecular features, the LG provide an excellent model to study the genetic mechanisms underlying glial subtype differentiation and diversity, glial morphogenesis and neuron-glial interactions during development. In addition, they are proving useful in understanding how glial cells maintain ion and neurotransmitter homeostasis and protect neurons from environmental insult.     

Direct analysis of the extracellular proteome from two strains of Helicobacter pylori

Helicobacter pylori extracellular proteins are of interest because of possible roles in pathogenesis, host recognition, and vaccine development. We utilized a unique approach by growing two strains (including one nonsequenced strain) in a defined serum-free medium and directly analyzing the proteins present in the culture supernatants by LC-MS/MS. Over 125 proteins were identified in the extracellular proteomes of two H. pylori strains. Forty-five of these proteins were enriched in the extracellular fraction when compared to soluble cell-associated protein samples. Our analysis confirmed and expanded on the previously reported H. pylori extracellular proteome. Extracellular proteins of interest identified here included cag pathogenicity island protein Cag24 (CagD); proteases HP0657 and HP1012; a polysaccharide deacetylase, HP0310, possibly involved in the hydrolysis of acetyl groups from host N-acetylglucosamine residues or from residues on the cell surface; and HP0953, an uncharacterized protein that appears to be restricted to Helicobacter species that colonize the gastric mucosa. In addition, our analysis found eight previously unidentified outer membrane proteins and two lipoproteins that could be important cell surface proteins.     

Plasmodium strain determines dendritic cell function essential for survival from malaria

The severity of malaria can range from asymptomatic to lethal infections involving severe anaemia and cerebral disease. However, the molecular and cellular factors responsible for these differences in disease severity are poorly understood. Identifying the factors that mediate virulence will contribute to developing antiparasitic immune responses. Since immunity is initiated by dendritic cells (DCs), we compared their phenotype and function following infection with either a nonlethal or lethal strain of the rodent parasite, Plasmodium yoelii, to identify their contribution to disease severity. DCs from nonlethal infections were fully functional and capable of secreting cytokines and stimulating T cells. In contrast, DCs from lethal infections were not functional. We then transferred DCs from mice with nonlethal infections to mice given lethal infections and showed that these DCs mediated control of parasitemia and survival. IL-12 was necessary for survival. To our knowledge, our studies have shown for the first time that during a malaria infection, DC function is essential for survival. More importantly, the functions of these DCs are determined by the strain of parasite. Our studies may explain, in part, why natural malaria infections may have different outcomes.     

Increased insulin-stimulated Akt pSer473 and cytosolic SHP2 protein abundance in human skeletal muscle following acute exercise and short-term training.

The purpose of the present study was to determine in human skeletal muscle whether a single exercise bout and 7 days of consecutive endurance (cycling) training 1) increased insulin-stimulated Akt pSer(473) and 2) altered the abundance of the protein tyrosine phosphatases (PTPases), PTP1B and SHP2. In healthy, untrained men (n = 8; 24 +/- 1 yr), glucose infusion rate during a hyperinsulinemic euglycemic clamp, when compared with untrained values, was not improved 24 h following a single 60-min bout of endurance cycling but was significantly increased ( approximately 30%; P < 0.05) 24 h following completion of 7 days of exercise training. Insulin-stimulated Akt pSer(473) was approximately 50% higher (P < 0.05) 24 h following the acute bout of exercise, with this effect remaining after 7 days of training (P < 0.05). Insulin-stimulated insulin receptor and insulin receptor substrate-1 tyrosine phosphorylation were not altered 24 h after acute exercise and short-term training. Insulin did not acutely regulate the localization of the PTPases, PTP1B or SHP2, although cytosolic protein abundance of SHP2 was increased (P < 0.05; main effect) 24 h following acute exercise and short-term training. In conclusion, insulin-sensitive Akt pSer(473) and cytosolic SHP2 protein abundance are higher after acute exercise and short-term training, and this effect appears largely due to the residual effects of the last bout of prior exercise. The significance of exercise-induced alterations in cytosolic SHP2 and insulin-stimulated Akt pSer(473) on the improvement in insulin sensitivity requires further elucidation.     

Control of Echinothrips americanus on lima bean by Franklinothrips vespiformis crawford using supplemental food

BioControl - Supplemental food application to crops as a resource for generalist predators has shown utility for promoting their establishment and persistence leading to enhanced biological control...