Roles for Drosophila melanogaster myosin IB in maintenance of enterocyte brush-border structure and resistance to the bacterial pathogen Pseudomonas entomophila

Author Posting. © American Society for Cell Biology, 2007. This article is posted here by permission of American Society for Cell Biology for personal use, not for redistribution. The definitive version was published in Molecular Biology of the Cell 18 (2007): 4625-4636, doi:10.1091/mbc.E07-02-0191.Drosophila myosin IB (Myo1B) is one of two class I myosins in the Drosophila genome. In the larval and adult midgut enterocyte, Myo1B is present within the microvillus (MV) of the apical brush border (BB) where it forms lateral tethers between the MV membrane and underlying actin filament core. Expression of green fluorescent protein-Myo1B tail domain in the larval gut showed that the tail domain is sufficient for localization of Myo1B to the BB. A Myo1B deletion mutation exhibited normal larval gut physiology with respect to food uptake, clearance, and pH regulation. However, there is a threefold increase in terminal deoxynucleotidyl transferase dUTP nick-end labeling-positive enterocyte nuclei in the Myo1B mutant. Ultrastructural analysis of mutant midgut revealed many perturbations in the BB, including membrane tethering defects, MV vesiculation, and membrane shedding. The apical localization of both singed (fascin) and Dmoesin is impaired. BBs isolated from mutant and control midgut revealed that the loss of Myo1B causes the BB membrane and underlying cytoskeleton to become destabilized. Myo1B mutant larvae also exhibit enhanced sensitivity to oral infection by the bacterial pathogen Pseudomonas entomophila, and severe cytoskeletal defects are observed in the BB of proximal midgut epithelial cells soon after infection. Resistance to P. entomophila infection is restored in Myo1B mutant larvae expressing a Myo1B transgene. These results indicate that Myo1B may play a role in the local midgut response pathway of the Imd innate immune response to Gram-negative bacterial infection.This work was supported by National Institutes of Health grants DK-25387 (to M.S.M.), DK-55389 (to Jon Morrow, Yale School of Medicine), and GM-52857 (to L.G.T.) and a research grant from the Crohns and Colitis Foundation of America (to M.S.M.)

Core-level XPS spectra of supported 3d-metal ultrathin layers : experimental and theoretical studies

In order to discuss the relation between the core level c-XPS spectra and the local electronic and magnetic properties of supported 3d transition metal atoms, we incorporate the various Coulomb and exchange interactions into a generalized impurity Anderson Hamiltonian, both in the initial state (Udd, Jdd) and final state (Udc, Jdc) of the c-XPS process. Then we discuss recent experimental 3s-XPS spectra of Fe and Co ultrathin-layers upon Cr(100) as well as V clusters upon graphite in terms of the two limits of the preceding Hamiltonian : (1) the exchange splitting limit (Jdc) and (2) the dielectric relaxation limit (Udc)

Equisingularity and Simultaneous Resolution of Singularities

Zariski defined equisingularity on an n-dimensional hypersurface V via stratification by "dimensionality type," an integer associated to a point by means of a generic local projection to affine n-space. A possibly more intuitive concept of equisingularity can be based on stratification by simultaneous resolvability of singularities. The two approaches are known to be equivalent for families of plane curve singularities. In higher dimension we ask whether constancy of dimensionality type along a smooth subvariety W of V implies the existence of a simultaneous resolution of the singularities of V along W. (The converse is false.) The underlying idea is to follow the classical inductive strategy of Jung -- begin by desingularizing the discriminant of a generic projection -- to reduce to asking if there is a canonical resolution process which when applied to quasi-ordinary singularities depends only on their characteristic monomials. This appears to be so in dimension 2. In higher dimensions the question i