Positive regulation of interleukin-4-mediated proliferation by the SH2-containing inositol-5'-phosphatase

The SH2-containing inositol 5'-phosphatase (SHIP) is tyrosine-phosphorylated in response to cytokines such as interleukin (IL)-3, granulocyte-macrophage colony-stimulating factor, and macrophage colony-stimulating factor. SHIP has been shown to modulate negatively these cytokine signalings; however, a potential role in IL-4 signaling remains uncharacterized. It has been recently shown that IL-4 induces tyrosine phosphorylation of SHIP, implicating the phosphatase in IL-4 processes. Tyrosine kinases, Jak1 and Jak3, involved in IL-4 signaling can associate with SHIP, yet only Jak1 can tyrosine-phosphorylate SHIP when co-expressed. In functional studies, cells overexpressing wild type SHIP are found to be hyperproliferative in response to IL-4 in comparison to parental cells. In contrast, cells expressing catalytically inactive form, SHIP(D672A), show reduced proliferation in response to IL-4. These changes in IL-4-induced proliferation correlate with alterations in phosphatidylinositol 3,4,5-triphosphate levels. However, no differential activation of STAT6, Akt, IRS-2, or p70(S6k), in response to IL-4, was observed in these cells. These data suggest that the catalytic activity of SHIP acts in a novel manner to influence IL-4 signaling. In addition, these data support recent findings that suggest there are uncharacterized signaling pathways downstream of phosphatidylinositol 3,4,5-triphosphate.     

Exclusion of golgi residents from transport vesicles budding from Golgi cisternae in intact cells

A central feature of cisternal progression/maturation models for anterograde transport across the Golgi stack is the requirement that the entire population of steady-state residents of this organelle be continuously transported backward to earlier cisternae to avoid loss of these residents as the membrane of the oldest (trans-most) cisterna departs the stack. For this to occur, resident proteins must be packaged into retrograde-directed transport vesicles, and to occur at the rate of anterograde transport, resident proteins must be present in vesicles at a higher concentration than in cisternal membranes. We have tested this prediction by localizing two steady-state residents of medial Golgi cisternae (mannosidase II and N-acetylglucosaminyl transferase I) at the electron microscopic level in intact cells. In both cases, these abundant cisternal constituents were strongly excluded from buds and vesicles. This result suggests that cisternal progression takes place substantially more slowly than most protein transport and therefore is unlikely to be the predominant mechanism of anterograde movement.     

The use of pHluorins for optical measurements of presynaptic activity

Genetically encoded reporters for optical measurements of presynaptic activity hold significant promise for measurements of neurotransmission within intact or semi-intact neuronal networks. We have characterized pH-sensitive green fluorescent protein-based sensors (pHluorins) of synaptic vesicle cycling at nerve terminals. pHluorins have a pK approximately 7.1, which make them ideal for tracking synaptic vesicle lumen pH upon cycling through the plasma membrane during action potentials. A theoretical analysis of the expected signals using this approach and guidelines for future reporter development are provided.     

Asymmetric PI3K Activity in Lymphocytes Organized by a PI3K-Mediated Polarity Pathway

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High urine 1-hydroxypyrene glucuronide concentrations in Linxian,China, an area of high risk for squamous oesophageal cancer

Most squamous cell carcinomas of the oesophagus in low-risk populations are attributable to alcohol and tobacco consumption, but the aetiologic agents in many high-risk populations have yet to be definitively identified. Linxian, China has some of the highest oesophageal cancer rates in the world. Recent studies suggest that an association exists between high-level exposure to carcinogenic polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene (B[a]P), and the development of oesophageal cancer. The inhabitants of this high-risk region extensively use coal and wood for cooking and heating in unvented stoves, and thus may be exposed to PAHs produced during the incomplete combustion of these fuel sources. High levels of B[a]P were recently detected in staple food samples from Linxian and histopathologic changes that may be associated with PAH exposure have also been identified in oesophagectomy specimens from the region. In an effort to determine whether this high-risk population is exposed to high levels of PAHs, voided urines from non-smokers (n = 22) without occupational exposure were collected and analysed using immunoaffinity chromatography and synchronous fluorescence spectroscopy for 1-hydroxypyrene glucuronide, a PAH metabolite and index biomarker for mixed PAH exposure. The median urine 1-hydroxypyrene glucuronide concentration (2.06 pmol ml^-1) was equivalent to concentrations detected in current smokers. To the authors' knowledge, this represents the first report of elevated urine 1-hydroxpyrene glucuronide concentrations in Linxian, and the first biologic confirmation that the inhabitants of this rural, non-industrial, high oesophageal cancer risk region are exposed to carcinogenic PAHs.     

Effect of Iboga Alkaloids on μ-Opioid Receptor-Coupled G Protein Activation

Objective

The iboga alkaloids are a class of small molecules defined structurally on the basis of a common ibogamine skeleton, some of which modify opioid withdrawal and drug self-administration in humans and preclinical models. These compounds may represent an innovative approach to neurobiological investigation and development of addiction pharmacotherapy. In particular, the use of the prototypic iboga alkaloid ibogaine for opioid detoxification in humans raises the question of whether its effect is mediated by an opioid agonist action, or if it represents alternative and possibly novel mechanism of action. The aim of this study was to independently replicate and extend evidence regarding the activation of μ-opioid receptor (MOR)-related G proteins by iboga alkaloids.

Methods

Ibogaine, its major metabolite noribogaine, and 18-methoxycoronaridine (18-MC), a synthetic congener, were evaluated by agonist-stimulated guanosine-5´-O-(γ-thio)-triphosphate ([³⁵S]GTPγS) binding in cells overexpressing the recombinant MOR, in rat thalamic membranes, and autoradiography in rat brain slices.

Results And Significance

In rat thalamic membranes ibogaine, noribogaine and 18-MC were MOR antagonists with functional Ke values ranging from 3 uM (ibogaine) to 13 uM (noribogaine and 18MC). Noribogaine and 18-MC did not stimulate [³⁵S]GTPγS binding in Chinese hamster ovary cells expressing human or rat MORs, and had only limited partial agonist effects in human embryonic kidney cells expressing mouse MORs. Ibogaine did not did not stimulate [³⁵S]GTPγS binding in any MOR expressing cells. Noribogaine did not stimulate [³⁵S]GTPγS binding in brain slices using autoradiography. An MOR agonist action does not appear to account for the effect of these iboga alkaloids on opioid withdrawal. Taken together with existing evidence that their mechanism of action also differs from that of other non-opioids with clinical effects on opioid tolerance and withdrawal, these findings suggest a novel mechanism of action, and further justify the search for alternative targets of iboga alkaloids.     

PARASITISM VERSUS COMMENSALISM: THE CASE OF TABULATE ENDOBIONTS

Abstract:  Tube-like traces of organisms belonging to the ichnogenus Chaetosalpinx Sokolov have been considered in the literature as commensal endobiontic organisms of tabulate corals. Their position between the corallites (or sometimes within the septa), perforation of the host's skeleton and soft tissue, modification of its phenotype and a possible inhibition of its growth show that the relationship between these organisms and tabulate corals can best be interpreted as parasitism rather than commensalism, as previously suggested. Such an interpretation may be extended to the ichnogenera Helicosalpinx Oekentorp and Actinosalpinx Sokolov, which show identical placement within the host colony and similar features, such as the absence of their own wall.