Impact of the TCR Signal on Regulatory T Cell Homeostasis,Function, and Trafficking

Signaling through the T cell antigen receptor (TCR) is important for the homeostasis of naïve and memory CD4⁺ T cells. The significance of TCR signaling in regulatory T (Treg) cells has not been systematically addressed. Using an Ox40-cre allele that is prominently expressed in Treg cells, and a conditional null allele of the gene encoding p56^Lck, we have examined the importance of TCR signaling in Treg cells. Inactivation of p56^Lck resulted in abnormal Treg homeostasis characterized by impaired turnover, preferential redistribution to the lymph nodes, loss of suppressive function, and striking changes in gene expression. Abnormal Treg cell homeostasis and function did not reflect the involvement of p56^Lck in CD4 function because these effects were not observed when CD4 expression was inactivated by Ox40-cre.The results make clear multiple aspects of Treg cell homeostasis and phenotype that are dependent on a sustained capacity to signal through the TCR.     

Influence of Ca2+ and Mg2+ on the turnover of the phosphomonoester group of phosphatidylinositol 4-phosphate in human erythrocyte membranes.

In isolated erythrocyte membranes, increasing the free Mg2+ concentration from 0.5 to 10 mM progressively activates the membrane-bound phosphatidylinositol (PtdIns) kinase and leads to the establishment of a new equilibrium with higher phosphatidylinositol 4-phosphate (PtdIns4P) and lower PtdIns concentrations. The steady-state turnover of the phosphomonoester group of PtdIns4P also increases at high Mg2+ concentrations, indicating a simultaneous activation of PtdIns4P phosphomonoesterase by Mg2+. Half-maximum inhibition of PtdIns kinase occurs at 10 microM free Ca2+ in the presence of physiological free Mg2+ concentrations. Increasing free Mg2+ concentrations overcome Ca2+ inhibition of PtdIns kinase. In the presence of Ca2+, calmodulin activates Ca2+-transporting ATPase 5-fold, but does not alter pool size and radiolabelling of PtdIns4P. In intact erythrocytes, adding EGTA or EGTA plus Mg2+ and the ionophore A23187 to the external medium does not exert significant effects on concentration and radiolabelling of polyphosphoinositides when compared with controls in the presence of 1.4 mM free Ca2+.     

Localization of the human gene allowing infection by gibbon ape leukemia virus to human chromosome region 2q11-q14 and to the homologous region on mouse chromosome 2.

Retrovirus receptors remain a largely unexplored group of proteins. Of the receptors which allow infection of human and murine cells by various retroviruses, only three have been identified at the molecular level. These receptors include CD4 for human immunodeficiency virus, Rec-1 for murine ecotropic virus, and GLVR1 for gibbon ape leukemia virus. These three proteins show no homology to one another at the DNA or protein level. Therefore, work to date has not shown any general relationship or structural theme shared by retroviral receptors. Genes for two of these receptors (CD4 and Rec-1) and several others which have not yet been cloned have been localized to specific chromosomes. In order to assess the relationship between GLVR1 and other retroviral receptors, we mapped the chromosome location of GLVR1 in human and mouse. GLVR1 was found to map to human chromosome 2q11-q14 by in situ hybridization and somatic-cell hybrid analysis. This location is distinct from those known for receptors for retroviruses infecting human cells. Glvr-1 was then mapped in the mouse by interspecies backcrosses and found to map to chromosome 2 in a region of linkage conservation with human chromosome 2. This mouse chromosome carries Rec-2, the likely receptor for M813, a retrovirus derived from a feral Asian mouse. These data raise the interesting possibility that Rec-2 and Glvr-1 are structurally related.     

Evidence for an increased rate of choline efflux across erythrocyte membranes in Alzheimer's disease

Alzheimer's disease (AD), the major dementing disorder of the elderly, is associated with cholinergic neuronal loss and decreased activity of choline acetyl-transferase (CAT). Previous biophysical studies had suggested an altered conformation of membrane proteins in AD erythrocyte ghosts. Since erythrocytes have a choline transport system and cholinergic neurons are implicated in AD, the present experiments were undertaken to determine if the efflux rate of [¹⁴C]choline was altered in AD erythrocytes. The mean efflux rate constant was highly significantly increased (P<0.01) by greater than 25% in 9 drug-free AD patients compared to 9 sex-matched, drug-free controls of similar age. These results are discussed in terms of potential molecular mechanisms to account for cholinergic neuronal loss in AD.     

Cholesterol Synthesis and Nerve Regeneration

Abstract: In this report, we examine the requirement of cholesterol biosynthesis and its axonal transport for goldfish optic nerve regeneration. Cholesterol, labeled by intraocular injection of [³H]mevalonolactone. exhibited a delayed appearance in the optic tectum. Squalene and other minor components were labeled but not transported. Following optic nerve crush, the amount of labeled cholesterol transport was elevated, while retinal labeling was not altered relative to control fish. A requirement for cholesterol biosynthesis is inferred from the inhibition of neurite outgrowth in retinal explants caused by the cholesterol synthesis inhibitor, 20, 25-diazacholes-terol. The inhibition of growth could be overcome by addition of mevalonolactone, but not cholesterol, to the medium. Intraperitoneal administration of 200 nmol of dia-zacholesterol resulted in 92-98% inhibition of retinal cholesterol synthesis and accumulation of labeled des-mosterol and other lipids in fish retina and brain which persisted for 2 weeks. Diazacholesterol-treated fish showed no reduction in the amount of lipid-soluble radioactivity transported following intraocular injection of [³H]mevalonolactone, but there were alterations in the chromatographic pattern of the transported labeled lipids. In contrast to its effects on neurite outgrowth in vitro , diazacholesterol did not inhibit optic nerve regeneration in vivo , as measured both by arrival of labeled rapidly transported protein at the tectum and by time required for the return of visual function.     

Blood characteristics of white-tailed deer from northeastern Kansas

Blood samples were collected from 118 white-tailed deer (Odocoileus virginianus) shot on the Fort Riley Military Installation in northeastern Kansas. Values for these deer for hematocrit, glucose, alkaline phosphatase, uric acid, total protein, albumin, and calcium were within the ranges reported in previous studies for undrugged white-tailed deer. Abnormally high concentrations of serum glutamic oxaloacetate transaminase (SGOT) and lactic dehydrogenase (LDH) were attributed to general trauma and tissue damage caused by shooting the deer. Fawns had higher concentrations of alkaline phosphatase than adults and had lower concentrations in winter than at other times of the year. Serum urea nitrogen (SUN) concentrations fluctuated seasonally. Elevated concentrations of SUN in adult males killed in December were attributed to an increased catabolism of muscle protein caused by low dietary intake and high energy requirements during the rut. Cholesterol concentrations varied seasonally without regard to age or sex.