The redox-switch domain of Hsp33 functions as dual stress sensor

The redox-regulated chaperone Hsp33 is specifically activated upon exposure of cells to peroxide stress at elevated temperatures. Here we show that Hsp33 harbors two interdependent stress-sensing regions located in the C-terminal redox-switch domain of Hsp33: a zinc center sensing peroxide stress conditions and an adjacent linker region responding to unfolding conditions. Neither of these sensors works sufficiently in the absence of the other, making the simultaneous presence of both stress conditions a necessary requirement for Hsp33's full activation. Upon activation, Hsp33's redox-switch domain adopts a natively unfolded conformation, thereby exposing hydrophobic surfaces in its N-terminal substrate-binding domain. The specific activation of Hsp33 by the oxidative unfolding of its redox-switch domain makes this chaperone optimally suited to quickly respond to oxidative stress conditions that lead to protein unfolding.     

Protective Role of the Virus-Specific Immune Response for Development of Severe Neurologic Signs in Simian Immunodeficiency Virus-Infected Macaques

The pathogenesis of human immunodeficiency virus-associated motor and cognitive disorders is poorly understood. In this context both a protective and a harmful role of the immune system has been discussed. This question was addressed in the present study by correlating the occurrence of neurologic disease in simian immunodeficiency virus (SIV)-infected macaques with disease progression and the humoral and cellular intrathecal antiviral immune response. Overt neurologic signs consisting of ataxia and apathy were observed at a much higher frequency in rapid progressor animals (6 of 12) than in slow progressors (1 of 7). Whereas slow progressors mounted a strong antiviral antibody (Ab) response as evidenced by enzyme-linked immunosorbent and immunospot assays, neither virus-specific Ab titers nor Ab-secreting cells could be found in the cerebrospinal fluid (CSF) or brain parenchyma of rapid progressors. Similarly, increased infiltration of CD8⁺ T cells and cytotoxic T lymphocytes specific for viral antigens were detected only in the CSF of slow progressors. The finding that neurologic signs develop frequently in SIV-infected macaques in the absence of an antiviral immune response demonstrates that the immune system does not contribute to the development of motor disorders in these animals. Moreover, the lower incidence of neurologic symptoms in slow progressors with a strong intrathecal immune response suggests a protective role of the virus-specific immunity in immunodeficiency virus-induced central nervous system disease.     

Assignment and evaluation of ground beetle (Coleoptera: Carabidae) assemblages to sites on different scales in a grassland landscape

Carabid beetles and environmental parameters were investigated in 52 grassland sites with three replicate pitfall traps in each site and in the valley of the River Eider in Schleswig–Holstein (northern Germany) with 61 pitfall traps. Environmental parameters included water content of soil, sand content, organic matter content and pH. Ground beetle assemblages were derived by detrended correspondence analyses (DCA) and characterised by the specific environmental conditions as means for each assemblage. On the regional scale including all investigated sites of Schleswig–Holstein, five assemblages were differentiated. On the local scale including the investigated sites in the valley of the River Eider, three assemblages were found corresponding well with those found on the regional scale. Environmental conditions at the sites of the five assemblages were correlated with land use data, soil types, and water level stages provided by three maps of a geographic information system (GIS). The GIS maps were combined to develop smaller areas with land use, soil type and water level stage information. The characteristic environmental conditions were assigned to each area to derive the spatial distribution of the five ground beetle assemblages. Spatial prediction was correct for 65% of investigated sites. The potential area of each assemblage was estimated for the valley. The different grassland areas were evaluated as potential habitats for ground beetle species comparing total species richness with the regional species richness of each assemblage. The comparison shows that species richness in the evaluated assemblages is relatively low compared to the regional potential.     

Ultrastructural evidence for an osmoregulatory effect of nikkomycin in the mite Tetranychus urticae

Histological effects of the microbial metabolite and chitin synthesis inhibitor complex Nikkomycin (AMS 0896 Bayer Leverkusen) on osmoregulatory organs of all developmental stages of Tetranychus urticae are described. The metabolite, in a concentration of 100 ppm, was applied via the nutritive plant. Mites fed for 2 to 14 days, and then were collected and immediately fixed. Two osmoregulatory organs occur in T. urticae. The Malpighian complex, differentiated only in females, shows an increased number of apical microvilli in the epithelium of the distal regions after metabolite application, thus resulting in an enlargement of the surface area. Changes in the second osmoregulatory organ, the coxal organ, after Nikkomycin application include depositions of membranous bodies in the lumen as well as in cytoplasmic vacuoles of the proximal tubule. Additionally, an increase in the luminal diameter occurs. Numerous vacuoles of different contents are observed in the cytoplasm of the distal tubule. Consequences of histological alterations in osmoregulatory organs after Nikkomycin application are discussed with special reference to the composition of salivary secretions.     

Induction of Raf kinase inhibitor protein contributes to macrophage differentiation

Differential gene expression analysis of human blood monocytes has identified the Raf kinase inhibitor protein (RKIP) as a continuously upregulated gene in macrophage and dendritic cell maturation. Using realtime RT-PCR and Western blot analysis we were able to confirm the initial DNA-microarray findings of RKIP induction on mRNA and protein levels. RKIP upregulation in primary cells and overexpression in THP-1 cells did not alter ERK activity but strongly reduced the amount of the NFkappaB subunit p65 in the nucleus. mRNA levels and cell surface expression of maturation markers including the integrin CD11c and the scavenger receptor CD36 were significantly increased in RKIP transfected THP-1 cells. Our data show for the first time that RKIP is upregulated during macrophage and dendritic cell differentiation on mRNA and protein levels and we conclude that RKIP contributes to the monocytic differentiation process via inhibition of the NFkappaB signaling cascade independent from the canonical Ras/Raf/MEK/ERK pathway.     

Mapping and characterization of the primary and anamnestic H-2(d)-restricted cytotoxic T-lymphocyte response in mice against human metapneumovirus

Cytotoxic T lymphocytes (CTLs) are important for the control of virus replication during respiratory infections. For human metapneumovirus (hMPV), an H-2(d)-restricted CTL epitope in the M2-2 protein has been described. In this study, we screened the hMPV F, G, N, M, M2-1, and M2-2 proteins using three independent algorithms to predict H-2(d) CTL epitopes in BALB/c mice. A dominant epitope (GYIDDNQSI) in positions 81 to 89 of the antitermination factor M2-1 and a subdominant epitope (SPKAGLLSL) in N(307-315) were detected during the anti-hMPV CTL response. Passive transfer of CD8(+) T-cell lines against M2-1(81-89) and N(307-315) protected Rag1(-/-) mice against hMPV challenge. Interestingly, diversification of CTL targets to include multiple epitopes was observed after repetitive infections. A subdominant response against the previously described M2-2 epitope was detected after the third infection. An understanding of the CTL response against hMPV is important for developing preventive and therapeutic strategies against the virus.     

Gq-coupled receptors as mechanosensors mediating myogenic vasoconstriction

Despite the central physiological function of the myogenic response, the underlying signalling pathways and the identity of mechanosensors in vascular smooth muscle (VSM) are still elusive. In contrast to present thinking, we show that membrane stretch does not primarily gate mechanosensitive transient receptor potential (TRP) ion channels, but leads to agonist-independent activation of G(q/11)-coupled receptors, which subsequently signal to TRPC channels in a G protein- and phospholipase C-dependent manner. Mechanically activated receptors adopt an active conformation, allowing for productive G protein coupling and recruitment of beta-arrestin. Agonist-independent receptor activation by mechanical stimuli is blocked by specific antagonists and inverse agonists. Increasing the AT(1) angiotensin II receptor density in mechanically unresponsive rat aortic A7r5 cells resulted in mechanosensitivity. Myogenic tone of cerebral and renal arteries is profoundly diminished by the inverse angiotensin II AT(1) receptor agonist losartan independently of angiotensin II (AII) secretion. This inhibitory effect is enhanced in blood vessels of mice deficient in the regulator of G-protein signalling-2. These findings suggest that G(q/11)-coupled receptors function as sensors of membrane stretch in VSM cells.