http://www.jbc.org/content/264/14/8179.full.pdf

Photochemically generated cytosolic calcium pulses and their detection by fluo-3.

The release of microparticles from eukaryotic cells is a well-recognized phenomenon. We demonstrate here that the chemokine receptor CCR5, the principal co-receptor for macrophage-tropic human immunodeficiency virus (HIV)-1, can be released through microparticles from the surface of CCR5+ Chinese hamster ovary cells and peripheral blood mononuclear cells. Microparticles containing CCR5 can transfer the receptor to CCR5- cells and render them CCR5+. The CCR5 transfer to CCR5-deficient peripheral blood mononuclear cells homozygous for a 32-base-pair deletion in the CCR5 gene enabled infection of these cells with macrophage-tropic HIV-1. In monocytes, the transfer of CCR5 could be inhibited by cytochalasin D, and transferred CCR5 could be downmodulated by chemokines. A transfer of CCR5 from peripheral blood mononuclear cells to endothelial cells during transendothelial migration could be demonstrated. Thus, the transfer of CCR5 may lead to infection of tissues without endogenous CCR5 expression. Moreover, the intercellular transfer of membrane proteins by microparticles might have broader consequences for intercellular communication beyond the effects seen for HIV-1.

Transfer of the chemokine receptor CCR5 between cells by membrane-derived microparticles: a mechanism for cellular human immunodeficiency virus 1 infection.

The restriction point (R-point) marks the critical event when a mammalian cell commits to proliferation and becomes independent of growth stimulation. It is fundamental for normal differentiation and tissue homeostasis, and seems to be dysregulated in virtually all cancers1,2. Although the R-point has been linked to various activities involved in the regulation of G1–S transition of the mammalian cell cycle2,3,4,5,6, the underlying mechanism remains unclear1,7. Using single-cell measurements, we show here that the Rb–E2F pathway functions as a bistable switch to convert graded serum inputs into all-or-none E2F responses. Once turned ON by sufficient serum stimulation, E2F can memorize and maintain this ON state independently of continuous serum stimulation. We further show that, at critical concentrations and duration of serum stimulation, bistable E2F activation correlates directly with the ability of a cell to traverse the R-point.

A bistable Rb-E2F switch underlies the restriction point.

Fluorescence ratio imaging of cytosolic free Na+ in individual fibroblasts and lymphocytes.

Human cytomegalovirus (HCMV) masterfully evades adaptive and innate immune responses, allowing infection to be maintained and periodically reactivated for the life of the host. Here we show that cells also possess an intrinsic immune defense against HCMV that is disarmed by the virus. In HCMV-infected cells, the promyelocytic leukemia nuclear body (PML-NB) protein Daxx silences viral immediate-early gene expression through the action of a histone deacetylase. However, this antiviral tactic is efficiently neutralized by the viral pp71 protein, which is incorporated into virions, delivered to cells upon infection, and mediates the proteasomal degradation of Daxx. This work demonstrates the mechanism through which pp71 activates viral immediate-early gene expression in HCMV-infected cells. Furthermore, it provides insight into how a PML-NB protein institutes an intrinsic immune defense against a DNA virus and how HCMV pp71 inactivates this defense.

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Inactivating a Cellular Intrinsic Immune Defense Mediated by Daxx Is the Mechanism through Which the Human Cytomegalovirus pp71 Protein Stimulates Viral Immediate-Early Gene Expression

Characterization of monoclonal antibodies and polyclonal immune sera directed against human cytomegalovirus virion proteins.

Host range temperature-conditional mutants in the adenovirus DNA binding protein are defective in the assembly of infectious virus

Transformation by adenovirus early region 2A temperature-sensitive mutants and their revertants

A mutation in the adenovirus type 5 DNA binding protein that fails to autoregulate the production of the DNA binding protein.

Temperature-independent revertants of adenovirus H5ts125 and H5ts107 mutants in the DNA binding protein: isolation of a new class of host range temperature conditional revertants.

Jean Claude Nicolas

Papers

Characterization of monoclonal antibodies and polyclonal immune sera directed against human cytomegalovirus virion proteins.

Host range temperature-conditional mutants in the adenovirus DNA binding protein are defective in the assembly of infectious virus

Transformation by adenovirus early region 2A temperature-sensitive mutants and their revertants

A mutation in the adenovirus type 5 DNA binding protein that fails to autoregulate the production of the DNA binding protein.

Temperature-independent revertants of adenovirus H5ts125 and H5ts107 mutants in the DNA binding protein: isolation of a new class of host range temperature conditional revertants.