Parkin uses the UPS to ship off dysfunctional mitochondria

Parkin is a ubiquitin E3 ligase that is implicated in familial Parkinson disease (PD). Previous studies have established its role in mitophagy, a pathway whereby dysfunctional mitochondria are targeted for autophagic degradation. We recently reported that a major function of Parkin in dysfunctional mitochondria is to activate the ubiquitin-proteasome system (UPS) for proteolysis of multiple outer membrane proteins, and that such activation of the UPS is a critical step in Parkin-mediated mitophagy. Here, we discuss the possible roles of the UPS in mitophagy and the pathogenesis of PD

Transitions from AFDC to SSI Prior to Welfare Reform – Policy Brief

The Supplemental Security Income (SSI) and Temporary Assistance for Needy Families (TANF) programs serve overlapping target groups. SSI serves adults and children with disabilities from low-income families, while TANF serves low-income families with children. Consequently, policy changes in one program can affect the other. The target group for Aid to Families with Dependent Children (AFDC), TANF’s predecessor, also overlapped with SSI’s target group. Many have anticipated that the replacement of AFDC with TANF in August 1996 would eventually increase SSI participation as TANF recipients with disabilities sought SSI benefits to avoid TANF work requirements and time limits

Vortex-like surface wave and its role in the transient phenomena of meta-material focusing

We show that a slab of meta-material (with $\epsilon=\mu=-1+i\Delta$) possesses a vortex-like surface wave with no ability to transport energy, whose nature is completely different from a localized mode or a standing wave. Through computations based on a rigorous time-dependent Green's function approach, we demonstrate that such a mode inevitably generates characteristic image oscillations in two dimensional focusing with even a monochromatic source, which were observed in many numerical simulations, but such oscillations are weak in three dimensional focusing.Comment: To appear in the March 7th issue of Appl. Phys. Let

Plasmonic modes of polygonal particles calculated using a quantum hydrodynamics method

Plasmonic resonances of nanoparticles have drawn lots of attentions due to their interesting and useful properties such as strong field enhancements. These systems are typically studied using either classical electrodynamics or fully quantum theory. Each approach can handle some aspects of plasmonic systems accurately and efficiently, while having its own limitation. The self-consistent hydrodynamics model has the advantage that it can incorporate the quantum effect of the electron gas into classical electrodynamics in a consistent way. We use the method to study the plasmonic response of polygonal particles under the influence of an external electromagnetic wave, and we pay particular attention to the size and shape of the particle and the effect of charging. We find that the particles support edge modes, face modes and hybrid modes. The charges induced by the external field in the edge (face) modes mainly localize at the edges (faces), while the induced charges in the hybrid modes are distributed nearly evenly in both the edges and faces. The edge modes are less sensitive to particle size than the face modes, but are sensitive to the corner angles of the edges. When the number of sides of regular polygons increases, the edge and face modes gradually change into the classical dipole plasmonic mode of a cylinder. The hybrid modes are found to be the precursor of the Bennett mode, which cannot be found in classical electrodynamics.Comment: 33 pages, 9 figure

Emerging functions of mammalian mitochondrial fusion and fission

Mitochondria provide a myriad of services to the cell, including energy production, calcium buffering and regulation of apoptosis. How these diverse functions are coordinated among the hundreds of mitochondria in a given cell is largely unknown, but is probably dependent on the dynamic nature of mitochondria. In this review, we explore the latest developments in mitochondrial dynamics in mammals. These studies indicate that mitofusins and OPA1 are essential for mitochondrial fusion, whereas Fis1 and Drp1 are essential for mitochondrial fission. The overall morphology of the mitochondrial population depends on the relative activities of these two sets of proteins. In addition to the regulation of mitochondrial shape, these molecules also play important roles in cell and tissue physiology. Perturbation of mitochondrial fusion results in defects in mitochondrial membrane potential and respiration, poor cell growth and increased susceptibility to cell death. These cellular observations may explain why mitochondrial fusion is essential for embryonic development. Two inherited neuropathies, Charcot–Marie–Tooth type 2A and autosomal dominant optic atrophy, are caused by mutations in mitofusin 2 and OPA1, suggesting that proper regulation of mitochondrial dynamics is particularly vital to neurons. Mitochondrial fission accompanies several types of apoptotic cell death and appears important for progression of the apoptotic pathway. These studies provide insight into how mitochondria communicate with one another to coordinate mitochondrial function and morphology

Optimal design of gas adsorption refrigerators for cryogenic cooling

The design of gas adsorption refrigerators used for cryogenic cooling in the temperature range of 4K to 120K was examined. The functional relationships among the power requirement for the refrigerator, the system mass, the cycle time and the operating conditions were derived. It was found that the precool temperature, the temperature dependent heat capacities and thermal conductivities, and pressure and temperature variations in the compressors have important impacts on the cooling performance. Optimal designs based on a minimum power criterion were performed for four different gas adsorption refrigerators and a multistage system. It is concluded that the estimates of the power required and the system mass are within manageable limits in various spacecraft environments

The Prefusogenic Intermediate of HIV-1 gp41 Contains Exposed C-peptide Regions

The human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein is composed of a complex between the surface subunit gp120, which binds to cellular receptors, and the transmembrane subunit gp41. Upon activation of the envelope glycoprotein by cellular receptors, gp41 undergoes conformational changes that mediate fusion of the viral and cellular membranes. Prior to formation of a fusogenic "trimer-of-hairpins" structure, gp41 transiently adopts a prefusogenic conformation whose structural features are poorly understood. An important approach toward understanding structural conformations of gp41 during HIV-1 entry has been to analyze the structural targets of gp41 inhibitors. We have constructed epitope-tagged versions of 5-Helix, a designed protein that binds to the C-peptide region of gp41 and inhibits HIV-1 membrane fusion. Using these 5-Helix variants, we examined which conformation of gp41 is the target of 5-Helix. We find that although 5-Helix binds poorly to native gp41, it binds strongly to gp41 activated by interaction of the envelope protein with either soluble CD4 or membrane-bound cellular receptors. This preferential interaction with activated gp41 results in the accumulation of 5-Helix on the surface of activated cells. These results strongly suggest that the gp41 prefusogenic intermediate is the target of 5-Helix and that this intermediate has a remarkably "open" structure, with exposed C-peptide regions. These results provide important structural information about this intermediate that should facilitate the development of HIV-1 entry inhibitors and may lead to new vaccine strategies

Instability of three dimensional conformally dressed black hole

The three dimensional black hole solution of Einstein equations with negative cosmological constant coupled to a conformal scalar field is proved to be unstable against linear circularly symmetric perturbations.Comment: 5 pages, REVTe

Power-law Behavior of High Energy String Scatterings in Compact Spaces

We calculate high energy massive scattering amplitudes of closed bosonic string compactified on the torus. We obtain infinite linear relations among high energy scattering amplitudes. For some kinematic regimes, we discover that some linear relations break down and, simultaneously, the amplitudes enhance to power-law behavior due to the space-time T-duality symmetry in the compact direction. This result is consistent with the coexistence of the linear relations and the softer exponential fall-off behavior of high energy string scattering amplitudes as we pointed out prevously. It is also reminiscent of hard (power-law) string scatterings in warped spacetime proposed by Polchinski and Strassler.Comment: 6 pages, no figure. Talk presented by Jen-Chi Lee at Europhysics Conference (EPS2007), Manchester, England, July 19-25, 2007. To be published by Journal of Physics: Conference Series