Ezrin, radixin, and moesin are dispensable for macrophage migration and cellular cortex mechanics.

The cellular cortex provides crucial mechanical support and plays critical roles during cell division and migration. The proteins of the ERM family, comprised of ezrin, radixin, and moesin, are central to these processes by linking the plasma membrane to the actin cytoskeleton. To investigate the contributions of the ERM proteins to leukocyte migration, we generated single and triple ERM knockout macrophages.

Recurrence of Pemphigus Vulgaris after Bilateral Breast Irradiation: A Case Report and Review of the Literature.

Pemphigus is a serious and rare chronic bullous autoimmune disease. It is characterized by mucocutaneous erosions secondary to autoantibodies directed against desmogleins 1 and 3, proteins involved in intercellular adhesion mechanisms. The occurrence of pemphigus is based on the triggering of genetic and external environmental factors such as drugs, infection, and more rarely radiotherapy.

Phagocytosis is coupled to the formation of phagosome-associated podosomes and a transient disruption of podosomes in human macrophages.

Phagocytosis consists in ingestion and digestion of large particles, a process strictly dependent on actin re-organization. Using synchronized phagocytosis of IgG-coated latex beads (IgG-LB), zymosan or serum opsonized-zymosan, we report the formation of actin structures on both phagocytic cups and closed phagosomes in human macrophages. Their lifespan, size, protein composition and organization are similar to podosomes.

Visualisation of HO penetration through skin indicates importance to develop pathway-specific epidermal sensing.

Elevated amounts of reactive oxygen species (ROS) including hydrogen peroxide (HO) are observed in the epidermis in different skin disorders. Thus, epidermal sensing of HO should be useful to monitor the progression of skin pathologies. We have evaluated epidermal sensing of HO in vitro, by visualising HO permeation through the skin.

HIV-1-Infected Human Macrophages, by Secreting RANK-L, Contribute to Enhanced Osteoclast Recruitment.

HIV-1 infection is frequently associated with low bone density, which can progress to osteoporosis leading to a high risk of fractures. Only a few mechanisms have been proposed to explain the enhanced osteolysis in the context of HIV-1 infection. As macrophages are involved in bone homeostasis and are critical host cells for HIV-1, we asked whether HIV-1-infected macrophages could participate in bone degradation.

Genetic engineering of Hoxb8-immortalized hematopoietic progenitors - a potent tool to study macrophage tissue migration.

Tumor-associated macrophages (TAMs) are detrimental in most cancers. Controlling their recruitment is thus potentially therapeutic. We previously found that TAMs perform protease-dependent mesenchymal migration in cancer, while macrophages perform amoeboid migration in other tissues.

The Protease-Dependent Mesenchymal Migration of Tumor-Associated Macrophages as a Target in Cancer Immunotherapy.

Macrophage recruitment is essential for tissue homeostasis but detrimental in most cancers. Tumor-associated macrophages (TAMs) play a key role in cancer progression. Controlling their migration is, thus, potentially therapeutic.

Rho/ROCK pathway inhibition by the CDK inhibitor p27(kip1) participates in the onset of macrophage 3D-mesenchymal migration.

Infiltration of macrophages into tissue can promote tumour development. Depending on the extracellular matrix architecture, macrophages can adopt two migration modes: amoeboid migration--common to all leukocytes, and mesenchymal migration--restricted to macrophages and certain tumour cells. Here, we investigate the initiating mechanisms involved in macrophage mesenchymal migration.

Macrophage mesenchymal migration requires podosome stabilization by filamin A.

Filamin A (FLNa) is a cross-linker of actin filaments and serves as a scaffold protein mostly involved in the regulation of actin polymerization. It is distributed ubiquitously, and null mutations have strong consequences on embryonic development in humans, with organ defects which suggest deficiencies in cell migration. We have reported previously that macrophages, the archetypal migratory cells, use the protease- and podosome-dependent mesenchymal migration mode in dense three-dimensional environments, whereas they use the protease- and podosome-independent amoeboid mode in more porous matrices.

Extracellular proteolysis in macrophage migration: losing grip for a breakthrough.

Macrophage tissue infiltration is a hallmark of several pathological situations including cancer, neurodegenerative disorders and chronic inflammation. Hence, deciphering the mechanisms of macrophage migration across a variety of tissues holds great potential for novel anti-inflammatory therapies. Leukocytes have long been thought to migrate through tissues by using the amoeboid (protease-independent) migration mode; however, recent evidence indicates that macrophages can use either the amoeboid or the mesenchymal (protease-dependent) migration mode depending on the environmental constraints.

Frustrated phagocytosis on micro-patterned immune complexes to characterize lysosome movements in live macrophages.

Lysosome mobilization is a key cellular process in phagocytes for bactericidal activities and trans-matrix migration. The molecular mechanisms that regulate lysosome mobilization are still poorly known. Lysosomes are hard to track as they move toward phagosomes throughout the cell volume.

Macrophage podosomes go 3D.

Macrophage tissue infiltration is a critical step in the immune response against microorganisms and is also associated with disease progression in chronic inflammation and cancer. Macrophages are constitutively equipped with specialized structures called podosomes dedicated to extracellular matrix (ECM) degradation. We recently reported that these structures play a critical role in trans-matrix mesenchymal migration mode, a protease-dependent mechanism.

HIV-1 Nef triggers macrophage fusion in a p61Hck- and protease-dependent manner.

Macrophages are a major target of HIV-1 infection. HIV-1-infected macrophages form multinucleated giant cells (MGCs) using poorly elucidated mechanisms. In this study, we show that MGC formation was reduced when human macrophages were infected with nef-deleted HIV-1.

SMF-1, SMF-2 and SMF-3 DMT1 orthologues regulate and are regulated differentially by manganese levels in C. elegans.

Manganese (Mn) is an essential metal that can exert toxic effects at high concentrations, eventually leading to Parkinsonism. A major transporter of Mn in mammals is the divalent-metal transporter (DMT1). We characterize here DMT1-like proteins in the nematode C.

[Tumoral calcinosis at an unusual site in a haemodialysis patient].

Background: Tumour-like calcinosis is a rare cause of tissue calcification in patients on maintenance haemodialysis for chronic renal failure. Its estimated incidence is between 0.5 and 7% of haemodialysis patients.

Hematopoietic cell kinase (Hck) isoforms and phagocyte duties - from signaling and actin reorganization to migration and phagocytosis.

The activity of hematopoietic cell kinase (Hck), a member of the Src family kinases, is modulated by regulatory mechanisms leading to distinct protein conformations with gradual levels of activity. Hck is mostly expressed in phagocytes as two isoforms, p59Hck and p61Hck, which show distinct subcellular localizations and trigger distinct phenotypes when expressed ectopically in fibroblasts. Hck has been reported to be involved in phagocytosis, adhesion and migration, and to regulate formation of membrane protrusions, lysosome exocytosis, podosome formation, and actin polymerization.

Activation of p61Hck triggers WASp- and Arp2/3-dependent actin-comet tail biogenesis and accelerates lysosomes.

Secretory lysosomes exist in few cell types, but various mechanisms are involved to ensure their mobilization within the cytoplasm. In phagocytes, lysosome exocytosis is a regulated phenomenon at least in part under the control of the phagocyte-specific and lysosome-associated Src-kinase p61Hck (hematopoietic cell kinase). We show here that p61Hck activation triggered polymerization of actin at the membrane of lysosomes, which resulted in F-actin structures similar to comet tails observed on endocytic vesicles.

Re-arrangements of podosome structures are observed when Hck is activated in myeloid cells.

Podosomes are adhesion structures with an extracellular matrix-degrading capacity mostly found in monocyte-derived cells. We have previously shown that the protein tyrosine kinase Hck, a member of the Src family, triggers the de novo formation of podosome rosettes in a lysosome-dependent manner when expressed in its constitutively active form. Hck is specifically expressed in myeloid cells.

Activation of the lysosome-associated p61Hck isoform triggers the biogenesis of podosomes.

Haematopoietic cell kinase (Hck) is a protein tyrosine kinase of the Src family specifically expressed in phagocytes as two isoforms, p59Hck and p61Hck, present at the plasma membrane and lysosomes, respectively. We report that ectopic expression of a constitutively active mutant of p61Hck (p61Hck(ca)) triggered the de novo formation of actin-rich rings at the ventral face of the cells that we characterized as bona fide podosome rosettes, structures involved in cell migration. Their formation required the adaptor domains and the kinase activity of p61Hck, the integrity of microfilament and microtubule networks and concerted action of Cdc42, Rac and Rho.

Stromal reaction in cutaneous melanoma.

Cutaneous melanoma is a highly malignant tumor type which is characterized by its tendency to give rise to metastases. Stromal relationships are essential for growth and metastasis of solid tumors. In cutaneous melanoma, microscopic level of invasion (Breslow index), overall architecture of cells (horizontal or vertical growth phase), angiogenesis, vessel invasion are morphological features which may carry prognostic significance.

Elastin-derived peptides upregulate matrix metalloproteinase-2-mediated melanoma cell invasion through elastin-binding protein.

Type I collagen mediates melanoma cells invasion through upregulation of matrix metalloproteinases-1 and -2 (MMP-1 and -2) expression and activation. We investigated here the contribution of elastin-derived peptides (ED), degradation products of elastin, the main component of elastic fibers in melanoma cells invasion and MMP-1 and -2 expression. Our results evidenced fragmentation of elastin at the invasive front of melanoma, particularly in the most invasive tumors where those fibers nearly totally vanished.

[Positive photobiological investigation in Jessner's lymphocytic infiltration of the skin].

Background: Jessner's lymphocytic infiltration of the skin is a rare and benign disorder. Its clinical course is cyclic with remissions and exacerbations. In this disease, photosensitivity was previously noticed by authors and recently demonstrated.

The metalloprotease-directed shedding of BP 180 (collagen XVII) from human keratinocytes in culture is unaffected by ceramide and cell-matrix interaction.

The constitutive shedding of BP180 (collagen XVII) from human keratinocytes in culture was totally prevented by batimastat (5 microM), a wide spectrum matrix metalloprotease (MMP) inhibitor. However, keratinocytes did not express active MMP and generation of active Gelatinase A (MMP-2) and Gelatinase B (MMP-9) at the cell plasma membrane by increasing the ceramide content of keratinocytes did not influence BP180 processing to a 120 kDa species. A disintegrin and metalloprotease (ADAM) is probably involved in such a shedding event since release of 120 kDa polypeptide was inhibited by Decanoyl-Arg-Val-Lys-Arg CH2Cl (30 microM), a specific furin convertase inhibitor; culturing cells on to several matrix substrata i.

C. elegans dynamin-related protein DRP-1 controls severing of the mitochondrial outer membrane.

Little is known about the mechanism of mitochondrial division. We show here that mitochondria are disrupted by mutations in a C. elegans dynamin-related protein (DRP-1).