184 research outputs found
KK6 from M2 in BLG
We study the possibility that the Kaluza-Klein monopole (KK6) world-volume
action may be obtained from the multiple membranes (M2) action which is
described by BLG theory. We first point out that the infinite dimensional Lie
3-algebra based on the Nambu-Poisson structure could not only provide three
dimensional manifolds to allow M5 from M2, which was studied by previous
authors, but also provide five dimensional manifolds to allow KK6 from M2. We
next present a possible way that the U(1) field on KK6 world-volume action
could be produced form the gauge potential in BLG theory.Comment: Latex, 15 pages. V3: Add theorem 2 to complete proof. V4: Detail
physical interpretations and calculations in section
Einstein-Gauss-Bonnet black strings
We construct uniform black-string solutions in Einstein-Gauss-Bonnet gravity
for all dimensions between five and ten and discuss their basic properties.
Closed form solutions are found by taking the Gauss-Bonnet term as a
perturbation from pure Einstein gravity. Nonperturbative solutions are
constructed by solving numerically the equations of the model. The
Gregory-Laflamme instability of the black strings is explored via linearized
perturbation theory. Our results indicate that new qualitative features occur
for , in which case stable configurations exist for large enough values of
the Gauss-Bonnet coupling constant. For other dimensions, the black strings are
dynamically unstable and have also a negative specific heat. We argue that this
provides an explicit realization of the Gubser-Mitra conjecture, which links
local dynamical and thermodynamic stability. Nonuniform black strings in
Einstein-Gauss-Bonnet theory are also constructed in six spacetime dimensions.Comment: 33 pages, 11 figure
Conformal weights in the Kerr/CFT correspondence
It has been conjectured that a near-extreme Kerr black hole is described by a
2d CFT. Previous work has shown that CFT operators dual to axisymmetric
gravitational perturbations have integer conformal weights. In this paper, we
study the analogous problem in 5d. We consider the most general near-extreme
vacuum black hole with two rotational symmetries. This includes Myers-Perry
black holes, black rings and Kaluza-Klein black holes. We find that operators
dual to gravitational (or electromagnetic or massless scalar field)
perturbations preserving both rotational symmetries have integer conformal
weights, the same for all black holes considered.Comment: 19 page
Shoc2 Is Targeted to Late Endosomes and Required for Erk1/2 Activation in EGF-Stimulated Cells
Shoc2 is the putative scaffold protein that interacts with RAS and RAF, and positively regulates signaling to extracellular signal-regulated protein kinases 1 and 2 (ERK1/2). To elucidate the mechanism by which Shoc2 regulates ERK1/2 activation by the epidermal growth factor (EGF) receptor (EGFR), we studied subcellular localization of Shoc2. Upon EGFR activation, endogenous Shoc2 and red fluorescent protein tagged Shoc2 were translocated from the cytosol to a subset of late endosomes containing Rab7. The endosomal recruitment of Shoc2 was blocked by overexpression of a GDP-bound H-RAS (N17S) mutant and RNAi knockdown of clathrin, suggesting the requirement of RAS activity and clathrin-dependent endocytosis. RNAi depletion of Shoc2 strongly inhibited activation of ERK1/2 by low, physiological EGF concentrations, which was rescued by expression of wild-type recombinant Shoc2. In contrast, the Shoc2 (S2G) mutant, that is myristoylated and found in patients with the Noonan-like syndrome, did not rescue ERK1/2 activation in Shoc2-depleted cells. Shoc2 (S2G) was not located in late endosomes but was present on the plasma membrane and early endosomes. These data suggest that targeting of Shoc2 to late endosomes may facilitate EGFR-induced ERK activation under physiological conditions of cell stimulation by EGF, and therefore, may be involved in the spatiotemporal regulation of signaling through the RAS-RAF module
Rotating black rings on Taub-NUT
In this paper, we construct new solutions describing rotating black rings on
Taub-NUT using the inverse-scattering method. These are five-dimensional vacuum
space-times, generalising the Emparan-Reall and extremal Pomeransky-Sen'kov
black rings to a Taub-NUT background space. When reduced to four dimensions in
Kaluza-Klein theory, these solutions describe (possibly rotating) electrically
charged black holes in superposition with a finitely separated magnetic
monopole. Various properties of these solutions are studied, from both a five-
and four-dimensional perspective.Comment: 33 pages, 3 figures, LaTe
Counting all dyons in N =4 string theory
For dyons in heterotic string theory compactified on a six-torus, with
electric charge vector Q and magnetic charge vector P, the positive integer I =
g.c.d.(Q \wedge P) is an invariant of the U-duality group. We propose the
microscopic theory for computing the spectrum of all dyons for all values of I,
generalizing earlier results that exist only for the simplest case of I=1. Our
derivation uses a combination of arguments from duality, 4d-5d lift, and a
careful analysis of fermionic zero modes. The resulting degeneracy agrees with
the black hole degeneracy for large charges and with the degeneracy of
field-theory dyons for small charges. It naturally satisfies several physical
requirements including integrality and duality invariance. As a byproduct, we
also derive the microscopic (0,4) superconformal field theory relevant for
computing the spectrum of five-dimensional Strominger-Vafa black holes in ALE
backgrounds and count the resulting degeneracies
Generalized Weyl solutions in d=5 Einstein-Gauss-Bonnet theory: the static black ring
We argue that the Weyl coordinates and the rod-structure employed to
construct static axisymmetric solutions in higher dimensional Einstein gravity
can be generalized to the Einstein-Gauss-Bonnet theory. As a concrete
application of the general formalism, we present numerical evidence for the
existence of static black ring solutions in Einstein-Gauss-Bonnet theory in
five spacetime dimensions. They approach asymptotically the Minkowski
background and are supported against collapse by a conical singularity in the
form of a disk. An interesting feature of these solutions is that the
Gauss-Bonnet term reduces the conical excess of the static black rings.
Analogous to the Einstein-Gauss-Bonnet black strings, for a given mass the
static black rings exist up to a maximal value of the Gauss-Bonnet coupling
constant . Moreover, in the limit of large ring radius, the suitably
rescaled black ring maximal value of and the black string maximal
value of agree.Comment: 43 pages, 14 figure
MVB-12, a Fourth Subunit of Metazoan ESCRT-I, Functions in Receptor Downregulation
After ligand binding and endocytosis, cell surface receptors can continue to signal from endosomal compartments until sequestered from the cytoplasm. An important mechanism for receptor downregulation in vivo is via the inward budding of receptors into intralumenal vesicles to form specialized endosomes called multivesicular bodies (MVBs) that subsequently fuse with lysosomes, degrading their cargo. This process requires four heterooligomeric protein complexes collectively termed the ESCRT machinery. In yeast, ESCRT-I is a heterotetrameric complex comprised of three conserved subunits and a fourth subunit for which identifiable metazoan homologs were lacking. Using C. elegans, we identify MVB-12, a fourth metazoan ESCRT-I subunit. Depletion of MVB-12 slows the kinetics of receptor downregulation in vivo, but to a lesser extent than inhibition of other ESCRT-I subunits. Consistent with these findings, targeting of MVB-12 to membranes requires the other ESCRT-I subunits, but MVB-12 is not required to target the remaining ESCRT-I components. Both endogenous and recombinant ESCRT-I are stable complexes with a 1:1:1:1 subunit stoichiometry. MVB-12 has two human homologs that co-localize and co-immunoprecipitate with the ESCRT-I component TSG101. Thus, MVB-12 is a conserved core component of metazoan ESCRT-I that regulates its activity during MVB biogenesis
The von Hippel-Lindau Tumor Suppressor Protein Promotes c-Cbl-Independent Poly-Ubiquitylation and Degradation of the Activated EGFR
Somatic mutations or reduced expression of the von Hippel-Lindau (VHL) tumor suppressor occurs in the majority of the clear cell renal cell carcinoma (ccRCC) and is a causal factor for the pathogenesis of ccRCC. pVHL was reported to suppress the oncogenic activity of Epidermal Growth Factor Receptor (EGFR) by reducing the expression of the EGFR agonist TGF-α and by reducing the translation efficiency of EGFR itself. Furthermore, it was reported that pVHL down-regulates activated EGFR by promoting efficient lysosomal degradation of the receptor. These modes of negative regulation of EGFR by pVHL were dependent on Hypoxia Inducible Factor (HIF). In this study, we report that HIF was not the only factor stabilizing the activated EGFR in VHL-deficient ccRCC cells. Down-regulation of endogenous HIF in these cells had little effect on the turnover rates of the activated EGFR. Furthermore, neither pretreatment with lysomomal inhibitors pretreatment nor down-regulation of c-Cbl, a major E3 ubiquitin ligase that targets the activated EGFR for lysosomal degradation, significantly increased the stabilities of EGFR in VHL-expressing ccRCC cells. In contrast, pretreatment with proteasomal inhibitors extended EGFR lifetime and led to similar EGFR half-lives in VHL-expressing and VHL-deficient ccRCC cells. Down-regulation of c-Cbl in VHL-deficient ccRCC cells revealed that the c-Cbl and pVHL collaborated to down-regulate the activated EGFR. Finally, we found that pVHL promoted the poly-ubiquitylation of the activated EGFR, and this function was c-Cbl-independent. Thus these results indicate that pVHL limits EGFR signaling by promoting c-Cbl-independent poly-ubiquitylation of the activated receptor, which likely results in its degradation by proteasome
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