A RAB5/RAB4 recycling circuitry induces a proteolytic invasive program and promotes tumor dissemination

The mechanisms by which tumor cells metastasize and the role of endocytic proteins in this process are not well understood. We report that overexpression of the GTPase RAB5A, a master regulator of endocytosis, is predictive of aggressive behavior and metastatic ability in human breast cancers. RAB5A is necessary and sufficient to promote local invasion and distant dissemination of various mammary and nonmammary tumor cell lines, and this prometastatic behavior is associated with increased intratumoral cell motility. Specifically, RAB5A is necessary for the formation of invadosomes, membrane protrusions specialized in extracellular matrix (ECM) degradation. RAB5A promotes RAB4- and RABENOSYN-5–dependent endo/exocytic cycles (EECs) of critical cargos (membrane-type 1 matrix metalloprotease [MT1-MMP] and β3 integrin) required for invadosome formation in response to motogenic stimuli. This trafficking circuitry is necessary for spatially localized hepatocyte growth factor (HGF)/MET signaling that drives invasive, proteolysis-dependent chemotaxis in vitro and for conversion of ductal carcinoma in situ to invasive ductal carcinoma in vivo. Thus, RAB5A/RAB4 EECs promote tumor dissemination by controlling a proteolytic, mesenchymal invasive program.     

Endocytosis,Signaling, and Beyond

The endocytic network comprises a vast and intricate system of membrane-delimited cell entry and cargo sorting routes running between biochemically and functionally distinct intracellular compartments. The endocytic network caters to the organization and redistribution of diverse subcellular components, and mediates appropriate shuttling and processing of materials acquired from neighboring cells or the extracellular milieu. Such trafficking logistics, despite their importance, represent only one facet of endocytic function. The endocytic network also plays a key role in organizing, mediating, and regulating cellular signal transduction events. Conversely, cellular signaling processes tightly control the endocytic pathway at different steps. The present article provides a perspective on the intimate relationships that exist between particular endocytic and cellular signaling processes in mammalian cells, within the context of understanding the impact of this nexus on integrated physiology.Molecular mechanisms governing the remarkable diversity of endocytic routes and trafficking steps are described elsewhere in the literature (see Bissig and Gruenberg 2013; Henne et al. 2013; Burd and Cullen 2014; Gautreau et al. 2014; Kirchhausen et al. 2014; Mayor et al. 2014; Merrifield and Kaksonen 2014; Piper et al. 2014). Moreover, these have been the focus of many studies in the last 30 years, and the topic has been covered by many excellent reviews, making it unnecessary for us to dwell on this aspect any further here (see, for instance, Howes et al. 2010; McMahon and Boucrot 2011; Sandvig et al. 2011; Parton and del Pozo 2013). Herein, we will instead concentrate our attention on how cellular regulatory mechanisms control endocytosis, as well as on how endocytic events impinge on cell functions. Emphasis will be placed, although not exclusively, on studies that analyze cellular networks using holistic approaches and in vivo analysis. Our aim is to give the reader a flavor of the deep embedding of endocytic processes within cellular programs, a concept we refer to as the endocytic matrix (Scita and Di Fiore 2010).     

Leukocyte inhibitory factor activates human neutrophils and macrophages to release leukotriene B4 and thromboxanes

Recent evidence has proved that cytokines can stimulate the production of 5-lipoxygenase products. Leukotriene B4 (LTB4) is a major mediator of leukocyte activation in acute inflammatory reactions, which produce chemotaxis, lysosomal enzyme release, and cell aggregation. Leukocyte inhibitory factor (LIF) also causes biological responses related to inflammation, i.e., LIF directly induces specific granule secretion by polymorphonuclears (PMNs) and potentiates many formyl-methionyl-leucyl-phenylalanine (FMLPs) mediated responses. Since arachidonic acid products are important mediators of inflammation, we have studied the effects of LIF on the arachidonic acid cascade products LTB4 and thromboxane A2 (TxA2). Resuspended at a final concentration of greater than 95% polymorphonuclear PMNs were isolated and tested with some cytokines on the release of LTB4 and TxA2. Peripheral blood mononuclear cells were isolated and seeded in Petri dishes and incubated for 60 min. Adherent macrophages were used for the cytokine stimulation study. Both types of leukocytes were treated with LIF, interleukin 6 (IL 6), and granulocyte-monocyte colony stimulating factor (GM-CSF) at different concentrations, and test agents A23187 and FMLP. Radioimmunoassay for LTB4 and TxB2 was determined by the resulting supernatants. Treatment of PMNs and macrophages with LIF at different concentrations proved to generate significant increases in LTB4 and TxA2 production. This was compared with IL 6 and GM-CSF, which had no effects. In these experiments, TxA2 generations could not be attributed to platelet contamination of PMN suspensions. The quantity of platelet contamination was not sufficient to influence how much TxB2 was produced. The similarities of LIF to other arachidonate stimulating cytokines suggest a similar mode of action in producing hematologic changes typical of tissue injury.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hypoprolactinemic Action of Calcitonin and the Tuberoinfundibular Dopaminergic System

Abstract: The effects of calcitonin on neurochemical parameters related to the tuberoinfundibular dopaminergic system have been investigated in an attempt to elucidate how calcitonin decreases serum prolactin levels. Intracerebroventricular human or salmon calcitonin injection decreases serum prolactin, medial basal hypothalamic dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) and hypophysial DA and increases hypophysial DOPAC. Results suggest that calcitonin may decrease prolactin secretion via the tuberoinfundibular dopaminergic system.     

Protein nitration as footprint of oxidative stress-related nitric oxide signaling pathways in developing Ciona intestinalis

Developmental processes in the ascidian Ciona intestinalis depend on a complex interplay of events including, during metamorphosis, a caspase-dependent apoptosis which is regulated by the nitric oxide (NO)-cGMP signaling pathway. Herein we disclose an alternate NO-mediated signaling pathway during Ciona development which appears to be critically dependent on local redox control. Evidence in support of this conclusion includes: (a) inhibitors of NO synthase (NOS) and scavengers of NO-derived nitrating agents markedly decrease the rate of Ciona metamorphosis; (b) an NO donor or peroxynitrite caused an opposite effect; (c) increased protein nitration is observed at larva stage. Integrated proteomic and immunochemical methodologies identified nitrated tyrosine residues in ERK and snail. Overall, these results point to protein nitration as a hitherto overlooked NO-dependent regulatory mechanism in Ciona which is specifically triggered by elevated ROS production during developmental processes.     

Loss of negative regulation by Numb over Notch is relevant to human breast carcinogenesis

The biological antagonism between Notch and Numb controls the proliferative/differentiative balance in development and homeostasis. Although altered Notch signaling has been linked to human diseases, including cancer, evidence for a substantial involvement of Notch in human tumors has remained elusive. Here, we show that Numb-mediated control on Notch signaling is lost in approximately 50% of human mammary carcinomas, due to specific Numb ubiquitination and proteasomal degradation. Mechanistically, Numb operates as an oncosuppressor, as its ectopic expression in Numb-negative, but not in Numb-positive, tumor cells inhibits proliferation. Increased Notch signaling is observed in Numb-negative tumors, but reverts to basal levels after enforced expression of Numb. Conversely, Numb silencing increases Notch signaling in normal breast cells and in Numb-positive breast tumors. Finally, growth suppression of Numb-negative, but not Numb-positive, breast tumors can be achieved by pharmacological inhibition of Notch. Thus, the Numb/Notch biological antagonism is relevant to the homeostasis of the normal mammary parenchyma and its subversion contributes to human mammary carcinogenesis.     

Isolation of the human immunodeficiency virus (HIV) from the cerebro-spinal fluid

The authors describe a simple and available technique for HIV isolation from cerebrospinal fluid and report preliminary results obtained. Exposed data indicate that neurological involvement occurs early in the natural history of HIV infection and that the virus may be recovered in CSF at all stages of the disease, regardless of immunological conditions of patients. Virological evaluation of CSF may be important in understanding pathogenetic aspects of HIV infection and in clinical management of infected patients.     

Correlation of viral replication activity, the clinical phase of the disease and immunologic deterioration in HIV infection

The authors have studied the relationship among HIV replicative activity, expressed by HIV isolation from peripheral blood lymphocytes and p24 antigenemia detection, and the evolution of infection, in terms of stage of disease and T4 cells absolute number, in a group of 120 infected subjects. Data presented indicate that the expression of viral gene products is related both to clinical and immunological deterioration and suggest that viral replication plays a central role in the progression of the disease.