Pathogenic mycobacteria survive within macrophages by avoiding lysosomal delivery, instead residing in mycobacterial phagosomes. Upon infection, the leukocyte-specific protein coronin 1 is actively recruited to mycobacterial phagosomes, where it blocks lysosomal delivery by an unknown mechanism. Analysis of macrophages from coronin 1-deficient mice showed that coronin 1 is dispensable for F-actin-dependent processes such as phagocytosis, motility, and membrane ruffling. However, upon mycobacterial infection, coronin 1 was required for activation of the Ca(2+)-dependent phosphatase calcineurin, thereby blocking lysosomal delivery of mycobacteria. In the absence of coronin 1, calcineurin activity did not occur, resulting in lysosomal delivery and killing of mycobacteria. Furthermore, blocking calcineurin activation with cyclosporin A or FK506 led to lysosomal delivery and intracellular mycobacterial killing. These results demonstrate a role for coronin 1 in activating Ca(2+) dependent signaling processes in macrophages and reveal a function for calcineurin in the regulation of phagosome-lysosome fusion upon mycobacterial infection.

Our findings that PlGF is a cancer target and anti-PlGF is useful for anticancer treatment have been challenged by Bais et al. Here we take advantage of carcinogen-induced and transgenic tumor models as well as ocular neovascularization to report further evidence in support of our original findings of PlGF as a promising target for anticancer therapies. We present evidence for the efficacy of additional anti-PlGF antibodies and their ability to phenocopy genetic deficiency or silencing of PlGF in cancer and ocular disease but also show that not all anti-PlGF antibodies are effective. We also provide additional evidence for the specificity of our anti-PlGF antibody and experiments to suggest that anti-PlGF treatment will not be effective for all tumors and why. Further, we show that PlGF blockage inhibits vessel abnormalization rather than density in certain tumors while enhancing VEGF-targeted inhibition in ocular disease. Our findings warrant further testing of anti-PlGF therapies.

T cell homeostasis is essential for the functioning of the vertebrate immune system, but the intracellular signals required for T cell homeostasis are largely unknown. We here report that the WD-repeat protein family member coronin-1, encoded by the gene Coro1a, is essential in the mouse for T cell survival through its promotion of Ca2+ mobilization from intracellular stores. Upon T cell receptor triggering, coronin-1 was essential for the generation of inositol-1,4,5-trisphosphate from phosphatidylinositol-4,5-bisphosphate. The absence of coronin-1, although it did not affect T cell development, resulted in a profound defect in Ca2+ mobilization, interleukin-2 production, T cell proliferation and T cell survival. We conclude that coronin-1, through activation of Ca2+ release from intracellular stores, is an essential regulator of peripheral lymphocyte survival.

Coronin 1 is a member of the coronin protein family specifically expressed in leukocytes and accumulates at sites of rearrangements of the F-actin cytoskeleton. Here, we describe that coronin 1 molecules are coiled coil-mediated homotrimeric complexes, which associate with the plasma membrane and with the cytoskeleton via two distinct domains. Association with the cytoskeleton was mediated by trimerization of a stretch of positively charged residues within a linker region between the N-terminal, WD repeat-containing domain and the C-terminal coiled coil. In contrast, neither the coiled coil nor the positively charged residues within the linker domain were required for plasma membrane binding, suggesting that the N-terminal, WD repeat-containing domain mediates membrane interaction. The capacity of coronin 1 to link the leukocyte cytoskeleton to the plasma membrane may serve to integrate outside-inside signaling with modulation of the cytoskeleton. INTRODUCTIONCoronin 1 is expressed exclusively by leukocytes (Suzuki et al., 1995;Ferrari et al., 1999) and is a member of the WD repeat protein family termed coronins, which are collectively defined as F-actin-associated proteins widely expressed in the eukaryotic kingdom (de Hostos, 1999). In Dictyostelium discoideum, coronin colocalizes with F-actin filaments at crown-shaped phagocytic cups and macropinosomes (de Hostos et al., 1991(de Hostos et al., , 1993Maniak et al., 1995;Fukui et al., 1999). Dictyostelium deleted for coronin displays strong reduction in cell locomotion, phagocytosis, macropinocytosis, and cytokinesis, indicating that in this slime mold coronin is functionally involved in F-actin-based motility-related processes (de Hostos et al., 1993). In Saccharomyces cerevisiae, the single coronin isoform Crn1p was found to localize to cortical F-actin patches in an actin-dependent manner (Heil-Chapdelaine et al., 1998). In vitro, Crn1p can nucleate and cross-link F-actin filaments and bind to microtubules (Goode et al., 1999). Recently, yeast Crn1 was proposed to promote the formation of actin filament networks based on its interaction with the Arp2/3 complex (Humphries et al., 2002). Interestingly, unlike the Dictyostelium coronin-null mutant, an S. cerevisiae Crn1p-null-mutant does not show any phenotype in actin-dependent processes (Heil-Chapdelaine et al., 1998), suggesting that in this organism coronin does not perform an essential function in regulating the actin cytoskeleton. Although lower eukaryotes have one coronin gene, database searches have revealed the existence of several coronins in humans and mice (denoted coronins 1-7) (Okumura et al., 1998;de Hostos, 1999;Rybakin et al., 2004).In macrophages and lymphocytes, coronin 1 concentrates at sites of rearrangement of the cytoskeleton. In lymphocytes, coronin 1 assembles at the immunological synapse formed during activation of T-cells (Nal et al., 2004). In mouse macrophages, coronin 1 accumulates during phagocytosis at the cytosolic face of phagosomes and is actively retained by pathogenic mycoba...

IntroductionAngiogenesis is a complex process that leads to the formation of new blood vessels from existing ones. During embryogenesis, angiogenesis complements vasculogenesis, the production of new blood vessels from hematopoietic precursors. In the adult organism, angiogenesis takes place under normal conditions during the female reproductive cycle or under pathologic conditions, such as in tumor growth and wound healing. Secretion of angiogenic factors from the tumor mass induces the formation of blood vessels, which feed cancer cells with oxygen and nutrients. These vessels will eventually be used as a route for the spreading of metastases. 1 Several angiogenic factors have been described, including vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), transforming growth factor-␣ (TGF-␣), TGF-␤, hepatocyte growth factor (HGF), tumor necrosis factor, angiogenin, interleukin-8, and the angiopoietins. 2 The most prominent angiogenic factor is VEGF-A, a member of the VEGF family of growth factors also including placental growth factor and VEGF-B, -C, -D, and -E. 3 VEGFs bind to 3 related members of the VEGFR family, VEGFR-1, -2, and -3. The importance of VEGFs and their receptors is demonstrated by the phenotypes of the respective knockout mice. Indeed, Vegf-A and Vegfr-2 knockout mice show a failure in vasculature formation and die during embryogenesis, whereas Vegfr-1-deficient mice die of an overgrowth of blood vessels. 3 Fighting angiogenesis has become an attractive aim of cancer therapy. Indeed, targeting angiogenesis rather than directly addressing the tumor cells has the advantage that the same reagents can be applied to many different types of tumors. In addition, because of the low turnover rate of endothelial cells (ECs), they are less susceptible to become resistant to chemotherapy. 4 Several anti-VEGF treatment regimens already exist that can be combined with chemotherapy or radiotherapy. These treatments make use of VEGF inhibitors, such as antibodies against VEGF (bevacizumab), several small molecules inhibiting VEGFR-2 signaling, as well as soluble VEGF receptors that compete with the endogenous receptor for binding to VEGF. 5 However, because all these treatments have a relatively modest benefit for most cancer patients, there is still plenty of room for improvement.HGF is another potent angiogenic factor: the expression of HGF and its receptor c-Met correlates with tumor vascularization, 6 the production of VEGF in a variety of cells and tissues is induced by HGF, 7 and HGF can potentiate the activity of VEGF. [8][9][10] Furthermore, HGF leads to mobilization of endothelial progenitor cells, 11 and the expression of a soluble c-Met receptor (decoy Met) impairs tumor angiogenesis. 12 We have previously shown that HGF depends on a CD44 exon v6 containing isoform for the activation of c-Met on epithelial cells. 13 CD44 isoforms containing the variant exon v6 have been shown to be metastatic determinants. 14 The role of CD44v6 in metastasis results most probably from its coop...