Cutting edge: myeloid complement C3 enhances the humoral response to peripheral viral infection

HSV-1 is the causative agent of cutaneous lesions, commonly referred to as cold sores. Primary exposure to the virus ordinarily occurs through the periphery, in particular through abraded skin or mucosal membranes. Under certain circumstances (e.g., in neonatals or AIDS patients), the infection becomes disseminated, often with severe consequences. Spread of HSV-1 is limited by virus-specific Ab. The development of an efficient humoral response to the virus is dependent on innate immunity component complement C3. The liver is the major source of C3, but there are also extrahepatic origins of C3 such as lymphoid macrophages. In the present study, the significance of C3 synthesis by bone marrow-derived cells was assessed by the transfer of wild-type bone marrow into irradiated C3-deficient mice. Using these chimeric mice, extrahepatic C3 was determined sufficient to initiate specific Ab and memory responses to a peripheral HSV-1 infection.     

Role of dietary lysine, methionine, and arginine in the regulation of hypercholesterolemia in rabbits

These experiments were conducted to see whether the hypercholesterolemia produced by a diet enriched in lysine (Lys) and methionine (Met) can be reproduced by feeding these amino acids separately, and whether dietary arginine (Arg) counteracts their hypercholesterolemic effects. Another aim was to investigate the mechanisms involved in modulations of serum cholesterol levels by these amino acids. The results of this study, which were in agreement with the results of earlier experiments in our laboratory, showed that feeding a low-fat, cholesterol-free, semipurified amino acid diet enriched with Lys + Met to rabbits caused a marked increase in serum total and low density lipoprotein cholesterol and apolipoprotein B levels, whereas a similar diet enriched in essential ketogenic amino acids (EketoAA) resulted in a more moderate increase in these parameters. Supplementing the diet with either Lys or Met alone was also less effective in inducing hypercholesterolemia than increasing levels of both amino acids. Dietary Arg partially counteracted the hypercholesterolemic effect of Lys + Met but not that of the EketoAA or of Lys and Met fed separately. The growth performance of rabbits fed the Lys + Met diet was inferior to that of those fed the other diets. Liver total phospholipid levels and the ratio of phosphatidylcholine to phosphatidylethanolamine were higher in rabbits fed the Lys + Met-enriched diet than in those animals fed a diet in which Arg was supplemented. In conclusion, our results indicate that high levels of both Lys and Met are needed to cause a maximum elevation of serum cholesterol and that the moderately antihypercholesterolemic effect of Arg is seen only when both amino acids are supplemented. They also suggest that these essential amino acids may affect cholesterol metabolism partly through alteration of liver phospholipids.     

Apolipophorin-III-like protein expressed in the antenna of the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae)

Antennal proteins of the male fire ant (Solenopsis invicta) were analyzed by two-dimensional gel electrophoresis, with the objective of identifying pheromone-binding proteins, which have not previously been found in ant antennae. The major low-molecular weight protein found in the male fire ant antenna was subjected to Edman degradation to determine the N-terminal amino acid sequence. Degenerate PCR primers based on this sequence were used to obtain a cDNA sequence corresponding to the full-length protein sequence. In-gel trypsin digestion followed by MALDI-TOF mass spectrometry and HPLC-ESI/MS/MS demonstrated that the protein gel spot contained only the protein corresponding to the cDNA sequence obtained by PCR. The sequence is similar to apolipophorin-III, an exchangeable lipid-binding protein. Fire ant apolipophorin-III is expressed in the antenna as well as the head, thorax and abdomen.     

GAA repeat instability in Friedreich ataxia YAC transgenic mice

Friedreich ataxia (FRDA) is primarily caused by an unstable GAA repeat-expansion mutation within intron 1 of the FRDA gene. However, the exact mechanisms leading to this expansion and its consequences are not fully understood. To study the dynamics of this mutation, we have generated two lines of human FRDA YAC transgenic mice that contain GAA repeat expansions within the appropriate genomic context. We have detected intergenerational instability and age-related somatic instability in both lines, with pronounced expansions found in the cerebellum. The dynamic nature of our transgenic GAA repeats is comparable with previous FRDA patient somatic tissue data. However, there is a difference between our FRDA YAC transgenic mice and other trinucleotide-repeat mouse models, which do not show pronounced repeat instability in the cerebellum. This represents the first mouse model of FRDA GAA repeat instability that will help to dissect the mechanism of this repeat.     

In vivo ozone exposure induces antioxidant/stress-related responses in murine lung and skin

Lung and skin are the organs directly exposed to environmental pollution. Ozone (O(3)) is a toxic, oxidant air pollutant, and exposure has been shown to induce antioxidant depletion as well as oxidation of lipids and proteins within the outermost skin layer (stratum corneum) and the lung respiratory tract lining fluids (RTLFs). To further define skin and lung responses to O(3) exposure, SKH-1 hairless mice were exposed to either 0.8 ppm of O(3) (a level occasionally reached in very polluted areas) or ambient air 6 h/day for 6 consecutive days. O(3) exposure resulted in the depletion of alpha-tocopherol in lung and plasma and induction in both skin and lung of heme oxygenase 1, cyclooxygenase 2, and proliferating cell nuclear antigen. O(3)-exposed animals showed a similar extent of upregulation of COX-2 and PCNA in lung and skin, whereas HO-1 was more responsive in skin than in lung (7-fold induction vs. 2-fold induction). In addition to these measures of response to oxidative stress, O(3) exposure led to the activation of nuclear factor kappaB measured as IkappaBalpha phosphorylation in both tissues. We conclude that in this model, O(3) at high pollutant levels is able to affect both lung and skin biology, inducing depletion of alpha-tocopherol and inducing stress-related responses in both skin epidermis and respiratory tract epithelium.     

Rab9 GTPase regulates late endosome size and requires effector interaction for its stability

Rab9 GTPase resides in a late endosome microdomain together with mannose 6-phosphate receptors (MPRs) and the tail-interacting protein of 47 kDa (TIP47). To explore the importance of Rab9 for microdomain establishment, we depleted the protein from cultured cells. Rab9 depletion decreased late endosome size and reduced the numbers of multilamellar and dense-tubule-containing late endosomes/lysosomes, but not multivesicular endosomes. The remaining late endosomes and lysosomes were more tightly clustered near the nucleus, implicating Rab9 in endosome localization. Cells displayed increased surface MPRs and lysosome-associated membrane protein 1. In addition, cells showed increased MPR synthesis in conjunction with MPR missorting to the lysosome. Surprisingly, Rab9 stability on late endosomes required interaction with TIP47. Rabs are thought of as independent, prenylated entities that reside either on membranes or in cytosol, bound to GDP dissociation inhibitor. These data show that Rab9 stability is strongly influenced by a specific effector interaction. Moreover, Rab9 and the proteins with which it interacts seem critical for the maintenance of specific late endocytic compartments and endosome/lysosome localization.     

Functional morphology of prey capture in the sturgeon,Scaphirhynchus albus

Acipenseriformes (sturgeon and paddlefish) are basal actinopterygians with a highly derived cranial morphology that is characterized by an anatomical independence of the jaws from the neurocranium. We examined the morphological and kinematic basis of prey capture in the Acipenseriform fish Scaphirhynchus albus, the pallid sturgeon. Feeding pallid sturgeon were filmed in lateral and ventral views and movement of cranial elements was measured from video sequences. Sturgeon feed by creating an anterior to posterior wave of cranial expansion resulting in prey movement through the mouth. The kinematics of S. albus resemble those of other aquatic vertebrates: maximum hyoid depression follows maximum gape by an average of 15 ms and maximum opercular abduction follows maximum hyoid depression by an average of 57 ms. Neurocranial rotation was not a part of prey capture kinematics in S. albus, but was observed in another sturgeon species, Acipenser medirostris. Acipenseriformes have a novel jaw protrusion mechanism, which converts rostral rotation of the hyomandibula into ventral protrusion of the jaw joint. The relationship between jaw protrusion and jaw opening in sturgeon typically resembles that of elasmobranchs, with peak upper jaw protrusion occurring after peak gape.     

Rapid appearance of epistasis during adaptive divergence following colonization

Theory predicts that short-term adaptation within populations depends on additive (A) genetic effects, while gene-gene interactions 'epistasis (E)' are important only in long-term evolution. However, few data exist on the genetic architecture of adaptive variation, and the relative importance of A versus non-additive genetic effects continues to be a central controversy of evolutionary biology after more than 70 years of debate. To examine this issue directly, we conducted hybridization experiments between two populations of wild soapberry bugs that have strongly differentiated in 100 or fewer generations following a host plant shift. Contrary to expectation, we found that between-population E and dominance (D) have appeared quickly in the evolution of new phenotypes. Rather than thousands of generations, adaptive gene differences between populations have evolved in tens. Such complex genetic variation could underlie the seemingly extreme rates of evolution that are increasingly reported in many taxa. In the case of the soapberry bug, extraordinary ecological opportunity, rather than mortality, may have created hard selection for genetic variants. Because ultimate division of populations into genetic species depends on epistatic loss of hybrid compatibility, local adaptation based on E may accelerate macro-evolutionary diversification.     

A fundamental role for KChIPs in determining the molecular properties and trafficking of Kv4.2 potassium channels

Kv4 potassium channels regulate action potentials in neurons and cardiac myocytes. Co-expression of EF hand-containing Ca2+-binding proteins termed KChIPs with pore-forming Kv4 alpha subunits causes changes in the gating and amplitude of Kv4 currents (An, W. F., Bowlby, M. R., Betty, M., Cao, J., Ling, H. P., Mendoza, G., Hinson, J. W., Mattsson, K. I., Strassle, B. W., Trimmer, J. S., and Rhodes, K. J. (2000) Nature 403, 553-556). Here we show that KChIPs profoundly affect the intracellular trafficking and molecular properties of Kv4.2 alpha subunits. Co-expression of KChIPs1-3 causes a dramatic redistribution of Kv4.2, releasing intrinsic endoplasmic reticulum retention and allowing for trafficking to the cell surface. KChIP co-expression also causes fundamental changes in Kv4.2 steady-state expression levels, phosphorylation, detergent solubility, and stability that reconstitute the molecular properties of Kv4.2 in native cells. Interestingly, the KChIP4a isoform, which exhibits unique effects on Kv4 channel gating, does not exert these effects on Kv4.2 and negatively influences the impact of other KChIPs. We provide evidence that these KChIP effects occur through the masking of an N-terminal Kv4.2 hydrophobic domain. These studies point to an essential role for KChIPs in determining both the biophysical and molecular characteristics of Kv4 channels and provide a molecular basis for the dramatic phenotype of KChIP knockout mice.