Induction of "tissue" transglutaminase in HIV pathogenesis: evidence for high rate of apoptosis of CD4+ T lymphocytes and accessory cells in lymphoid tissues.

Peripheral blood mononuclear cells and lymphoid tissues from HIV-infected individuals display high levels of "tissue" transglutaminase (tTG) with respect to seronegative persons. In asymptomatic individuals, > 80% of the circulating CD4+ T cells synthesize tTG protein and the number of these cells matches the level of apoptosis detected in the peripheral blood mononuclear cells from the same patients. In HIV-infected lymph nodes tTG protein is localized in large number of cells (macrophages, follicular dendritic cells, and endothelial cells), showing distinctive morphological and biochemical features of apoptosis as well as in lymphocytes and syncytia. These findings demonstrate that during the course of HIV infection, high levels of apoptosis also occur in the accessory cells of lymphoid organs. The increased concentration of epsilon(gamma-glutamyl)lysine isodipeptide, the degradation product of tTG cross-linked proteins, observed in the blood of HIV-infected individuals demonstrates that the enzyme accumulated in the dying cells actively cross-links intracellular proteins. The enhanced levels of epsilon(gamma-glutamyl)lysine in the blood parallels the progression of HIV disease, suggesting that the isodipeptide determination might be a useful method to monitor the in vivo rate of apoptosis.

A rice homeobox gene, OSH1, is expressed before organ differentiation in a specific region during early embryogenesis.

Homeobox genes encode a large family of homeodomain proteins that play a key role in the pattern formation of animal embryos. By analogy, homeobox genes in plants are thought to mediate important processes in their embryogenesis, but there is very little evidence to support this notion. Here we described the temporal and spatial expression patterns of a rice homeobox gene, OSH1, during rice embryogenesis. In situ hybridization analysis revealed that in the wild-type embryo, OSH1 was first expressed at the globular stage, much earlier than organogenesis started, in a ventral region where shoot apical meristem and epiblast would later develop. This localized expression of OSH1 indicates that the cellular differentiation has already occurred at this stage. At later stages after organogenesis had initiated, OSH1 expression was observed in shoot apical meristem [except in the L1 (tunica) layer], epiblast, radicle, and their intervening tissues in descending strength of expression level with embryonic maturation. We also performed in situ hybridization analysis with a rice organless embryo mutant, orl1, that develops no embryonic organs. In the orl1 embryo, the expression pattern of OSH1 was the same as that in the wild-type embryo in spite of the lack of embryonic organs. This shows that OSH1 is not directly associated with organ differentiation, but may be related to a regulatory process before or independent of the organ determination. The results described here strongly suggest that, like animal homeobox genes, OSH1 plays an important role in regionalization of cell identity during early embryogenesis.

Organ-specific and Agamous-regulated expression and glycosylation of a pollen tube growth-promoting protein.

Transmitting tissue-specific (TTS) protein is a pollen tube growth-promoting and attracting glycoprotein located in the stylar transmitting tissue extracellular matrix of the pistil of tobacco. The TTS protein backbones have a deduced molecular mass of about 28 kDa, whereas the glycosylated stylar TTS proteins have apparent molecular masses ranging between 50 and 100 kDa. TTS mRNAs and proteins are ectopically produced in transgenic tobacco plants that express either a cauliflower mosaic virus (CaMV) 35S promoter-TTS2 transgene or a CaMV 35S-promoter-NAG1 (NAG1 = Nicotiana tabacum Agamous gene) transgene. However, the patterns of TTS mRNA and protein accumulation and the quality of the TTS proteins produced are different in these two types of transgenic plants. In 35S-TTS transgenic plants, TTS mRNAs and proteins accumulate constitutively in vegetative and floral tissues. However, the ectopically expressed TTS proteins in these transgenic plants accumulate as underglycosylated protein species with apparent molecular masses between 30 and 50 kDa. This indicates that the capacity to produce highly glycosylated TTS proteins is restricted to the stylar transmitting tissue. In 35S-NAG transgenic plants, NAG1 mRNAs accumulate constitutively in vegetative and floral tissues, and TTS mRNAs are induced in the sepals of these plants. Moreover, highly glycosylated TTS proteins in the 50- to 100-kDa molecular mass range accumulate in the sepals of these transgenic, 35S-NAG plants. These results show that the tobacco NAGI gene, together with other yet unidentified regulatory factors, control the expression of TTS genes and the cellular capacity to glycosylate TTS proteins, which are normally expressed very late in the pistil developmental pathway and function in the final stage of floral development. The sepals in the transgenic 35S-NAG plants also support efficient pollen germination and tube growth, similar to what normally occurs in the pistil, and this ability correlates with the accumulation of the highest levels of the 50- to 100-kDa glycosylated TTS proteins.

Mapping the protein regions responsible for the functional specificities of the Arabidopsis MADS domain organ-identity proteins.

The Arabidopsis MADS domain proteins AP1, AP3, PI, and AG specify floral organ identity. All of these proteins contain a MADS domain required for DNA binding and dimerization; a region termed L (linker between MADS domain and K domain), which plays an important role in dimerization specificity; the K domain, named for its similarity to the coiled-coil domain of keratin; and a C-terminal region of unknown function. To determine which regions of these proteins are responsible for their abilities to specify different organs, we have made a number of chimeric MADS box genes. The in vivo function of these chimeric genes was investigated by ectopic expression in transgenic Arabidopsis plants. The four proteins fall into two classes on the basis of regions responsible for their functional specificities. The L region and K domain define the functional specificities of AP3 and PI, while the MADS domain and L region define the functional specificities of AP1 and AG.

The cell wall components peptidoglycan and lipoteichoic acid from Staphylococcus aureus act in synergy to cause shock and multiple organ failure.

Although the incidence of Gram-positive sepsis has risen strongly, it is unclear how Gram-positive organisms (without endotoxin) initiate septic shock. We investigated whether two cell wall components from Staphylococcus aureus, peptidoglycan (PepG) and lipoteichoic acid (LTA), can induce the inflammatory response and multiple organ dysfunction syndrome (MODS) associated with septic shock caused by Gram-positive organisms. In cultured macrophages, LTA (10 micrograms/ml), but not PepG (100 micrograms/ml), induces the release of nitric oxide measured as nitrite. PepG, however, caused a 4-fold increase in the production of nitrite elicited by LTA. Furthermore, PepG antibodies inhibited the release of nitrite elicited by killed S. aureus. Administration of both PepG (10 mg/kg; i.v.) and LTA (3 mg/kg; i.v.) in anesthetized rats resulted in the release of tumor necrosis factor alpha and interferon gamma and MODS, as indicated by a decrease in arterial oxygen pressure (lung) and an increase in plasma concentrations of bilirubin and alanine aminotransferase (liver), creatinine and urea (kidney), lipase (pancreas), and creatine kinase (heart or skeletal muscle). There was also the expression of inducible nitric oxide synthase in these organs, circulatory failure, and 50% mortality. These effects were not observed after administration of PepG or LTA alone. Even a high dose of LTA (10 mg/kg) causes only circulatory failure but no MODS. Thus, our results demonstrate that the two bacterial wall components, PepG and LTA, work together to cause systemic inflammation and multiple systems failure associated with Gram-positive organisms.

The site of action of neuronal acidic fibroblast growth factor is the organ of Corti of the rat cochlea.

Here we show that the mature cochlear neurons are a rich source of acidic fibroblast growth factor (aFGF), which is expressed in the neuronal circuitry consisting of afferent and efferent innervation. The site of action of neuronal aFGF is likely to reside in the organ of Corti, where one of the four known FGF receptor (FGFR) tyrosine kinases--namely, FGFR-3 mRNA--is expressed. Following acoustic overstimulation, known to cause damage to the organ of Corti, a rapid up-regulation of FGFR-3 is evident in this sensory epithelium, at both mRNA and protein levels. The present results provide in vivo evidence for aFGF being a sensory neuron-derived, anterogradely transported factor that may exert trophic effects on a peripheral target tissue. In this sensory system, aFGF, rather than being a neurotrophic factor, seems to promote maintenance of the integrity of the organ of Corti. In addition, aFGF, released from the traumatized nerve endings, may be one of the first signals initiating protective recovery and repair processes following damaging auditory stimuli.