Activity-dependent α-Cleavage of Nectin-1 Is Mediated by A Disintegrin and Metalloprotease 10 (ADAM10)

Nectin-1 is known to undergo ectodomain shedding by α-secretase and subsequent proteolytic processing by γ-secretase. How secretase-mediated cleavage of nectin-1 is regulated in neuronal cells and how nectin-1 cleavage affects synaptic adhesion is poorly understood. We have investigated α-and γ-secretase-mediated processing of nectin-1 in primary cortical neurons and identified which protease acts as a α-secretase. We report here that NMDA receptor activation, but not stimulation of AMPA or metabotropic glutamate receptors, resulted in robust α- and γ-secretase cleavage of nectin-1 in mature cortical neurons. Cleavage of nectin-1 required influx of Ca²⁺ through the NMDA receptor, and activation of calmodulin, but was not dependent on calcium/calmodulin-dependent protein kinase II (CaMKII) activation. We found that ADAM10 is the major secretase responsible for nectin-1 ectodomain cleavage in neurons and the brain. These observations suggest that α- and γ-secretase processing of nectin-1 is a Ca²⁺/calmodulin-regulated event that occurs under conditions of activity-dependent synaptic plasticity and ADAM10 and γ-secretase are responsible for these cleavage events.     

Proteome analysis of rat liver mitochondria reveals a possible compensatory response to endotoxic shock

Organ failure induced by endotoxic shock has recently been associated with affected mitochondrial function. In this study, effects of in vivo lipopolysaccharide-challenge on protein patterns of rat liver mitochondria in treated animals versus controls were studied by two-dimensional electrophoresis (differential image gel electrophoresis). Significant upregulation was found for ATP-synthase alpha chain and superoxide dismutase [Mn]. Our data suggest that endotoxic shock mediated changes in the mitochondrial proteome contribute to a compensatory reaction (adaptation to endotoxic shock) rather than to a mechanism of cell damage.     

An obligate intermediate along the slow folding pathway of a group II intron ribozyme

Most RNA molecules collapse rapidly and reach the native state through a pathway that contains numerous traps and unproductive intermediates. The D135 group II intron ribozyme is unusual in that it can fold slowly and directly to the native state, despite its large size and structural complexity. Here we use hydroxyl radical footprinting and native gel analysis to monitor the timescale of tertiary structure collapse and to detect the presence of obligate intermediates along the folding pathway of D135. We find that structural collapse and native folding of Domain 1 precede assembly of the entire ribozyme, indicating that D1 contains an on-pathway intermediate to folding of the D135 ribozyme. Subsequent docking of Domains 3 and 5, for which D1 provides a preorganized scaffold, appears to be very fast and independent of one another. In contrast to other RNAs, the D135 ribozyme undergoes slow tertiary collapse to a compacted state, with a rate constant that is also limited by the formation D1. These findings provide a new paradigm for RNA folding and they underscore the diversity of RNA biophysical behaviors.     

Host refractoriness of the tobacco hornworm, Manduca sexta, to the braconid endoparasitoid Cotesia flavipes

Cotesia flavipes (Hymenoptera:Braconidae) is a gregarious endoparasitoid of several pyralid stemborer larvae of economic significance including the sugarcane borer, Diatraea saccharalis. In this study, the ability of this parasitoid to develop in a sphingid host, Manduca sexta, was tested. First, second, third, fourth, and even pharate fifth instar host tobacco hornworm larvae were readily parasitized by the female C. flavipes parasitoids but no wasp larvae hatched from the eggs in this refractory host. Instead, the parasitoid eggs were invariably encapsulated by the host's hemocytes and, ultimately, no parasitoids emerged from tobacco hornworm hosts. The first stages of encapsulation were evident at 2 h post-parasitization of the host M. sexta larvae, when the beginning stages of capsule formation were seen. The developmental fate of the host larvae with encapsulated parasitoids was variable. Most succumbed as abnormally small fifth instars or as post-wandering prepupal animals, while a few developed normally to the pupal stage. Dissection of all the larvae or pupae with encapsulated wasp eggs showed evidence of hemocytic encapsulation and melanization of the C. flavipes eggs. This report describes the association between C. flavipes and M. sexta, which appears to be an excellent model system for studying the physiological processes accompanying wasp egg encapsulation that result in death of the host as well as the parasitoid. Since the parasitoid egg never hatches, the system offers an excellent opportunity to identify and study the effects of parasitoid-injected polydnavirus and venom on host physiology.     

Expanding ART for treatment and prevention of HIV in South Africa: estimated cost and cost-effectiveness 2011-2050

Background

Antiretroviral Treatment (ART) significantly reduces HIV transmission. We conducted a cost-effectiveness analysis of the impact of expanded ART in South Africa.

Methods

We model a best case scenario of 90% annual HIV testing coverage in adults 15–49 years old and four ART eligibility scenarios: CD4 count <200 cells/mm³ (current practice), CD4 count <350, CD4 count <500, all CD4 levels. 2011–2050 outcomes include deaths, disability adjusted life years (DALYs), HIV infections, cost, and cost per DALY averted. Service and ART costs reflect South African data and international generic prices. ART reduces transmission by 92%. We conducted sensitivity analyses.

Results

Expanding ART to CD4 count <350 cells/mm³ prevents an estimated 265,000 (17%) and 1.3 million (15%) new HIV infections over 5 and 40 years, respectively. Cumulative deaths decline 15%, from 12.5 to 10.6 million; DALYs by 14% from 109 to 93 million over 40 years. Costs drop $504 million over 5 years and $3.9 billion over 40 years with breakeven by 2013. Compared with the current scenario, expanding to <500 prevents an additional 585,000 and 3 million new HIV infections over 5 and 40 years, respectively. Expanding to all CD4 levels decreases HIV infections by 3.3 million (45%) and costs by $10 billion over 40 years, with breakeven by 2023. By 2050, using higher ART and monitoring costs, all CD4 levels saves $0.6 billion versus current; other ART scenarios cost $9–194 per DALY averted. If ART reduces transmission by 99%, savings from all CD4 levels reach $17.5 billion. Sensitivity analyses suggest that poor retention and predominant acute phase transmission reduce DALYs averted by 26% and savings by 7%.

Conclusion

Increasing the provision of ART to <350 cells/mm3 may significantly reduce costs while reducing the HIV burden. Feasibility including HIV testing and ART uptake, retention, and adherence should be evaluated.     

Hormonal Modulation of the Cutaneous Initiation of Lordosis in Infant and Adult Rats

The purpose of these experiments is to compare the regional specificity (Experiment 1) and the hormonal modulation (Experiment 2) of the cutaneous initiation of lordosis in 4- to 6-day-old male and female rats (infants) and in 60- to 90-day-old female rats (adults). In Experiment 1, subjects were primed with 100 μg estradiol benzoate (EB) and 0.5 mg progesterone (P) and were denervated on the Waist (dermatomes L1-L3), Midriff (dermatomes T10-L3), Flanks (dermatomes L4-L6), or Sides (dermatomes T10-L6). In infants, there were no significant differences between males and females. Denervation of the Waist. Midriff, or Sides but not of the Flanks significantly decreased the percentage of subjects displaying lordosis, lordosis quotient (LQ), and mean lordosis duration; no significant differences were obtained among Waist-, Midriff-, or Sides-denervated infants. In contrast, denervation of the Sides but not of the Waist significantly decreased LQ and mean lordosis intensity among adults. In Experiment 2, Waist-denervated infants and their surgical Controls were treated either with 100 μg EB and 0.5 mg P or with the oil vehicle; Waist-denervated adults and their surgical Controls received either 100 or 10 μg EB (no P). Regardless of hormone treatment, denervation of the Waist significantly decreased LQ and lordosis duration in infants and decreased LQ and lordosis intensity in adults. In infants, the only effect of priming with EB and P was to increase the percentage of pups showing lordosis and lordosis duration among the surgical Controls. In contrast, priming with 100 μg EB significantly increased the percentage of rats displaying lordosis, LQ, and lordosis intensity among Waist-denervated adults. These data suggest that cutaneous input from the Waist is important for eliciting lordosis in both infant and adult rats, and that the importance of this input is modulated by hormone priming in adult but not infant rats.