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Dalton Trans. 2012 Jun 7; 41(21): 6419-30 The effects of treatment with bis(maltolato)oxovanadium(iv) (BMOV) on protein localization in membrane microdomains were investigated by comparing the effects of insulin and treatment with BMOV on the lateral motions and compartmentalization of individual insulin receptors (IR). In addition, effects of insulin and BMOV on the association of IR, phosphorylated IR (pIR) and phosphorylated insulin receptor substrate-1 (pIRS-1) with chemically-isolated plasma membrane microdomains on rat basophilic leukemia (RBL-2H3) cells were evaluated. Single particle tracking experiments indicate that individual quantum dot-labeled IR on RBL-2H3 cells exhibit relatively unrestricted lateral diffusion of approximately 1 × 10(-10) cm(2) s(-1) and are confined in approximately 475 nm diameter cell-surface membrane compartments. After treating of RBL-2H3 cells with 10 μM BMOV, IR lateral diffusion and the size of IR-containing membrane compartments is significantly reduced to 6 × 10(-11) cm(2) s(-1) and approximately 400 nm, respectively. BMOV treatment also increases the association of IR with low-density, detergent-resistant membrane fragments isolated using isopycnic sucrose-gradient centrifugation from 2.4% for untreated cells to 25.8% for cells treated with 10 μM BMOV. Additionally, confocal fluorescence microscopic imaging of live RBL-2H3 cells labeled with the phase sensitive aminonaphthylethenylpyridinium-based dye, Di-4-ANEPPDHQ, indicates that BMOV treatment, but not insulin treatment, decreases cell-surface plasma membrane lipid order while fluorescence correlation spectroscopy measurements suggest that BMOV treatment does not affect IR surface-density or insulin binding affinity. Finally, model studies using microemulsions of cetyltrimethylammonium bromide (CTAB) micelles and (1)H NMR spectroscopy show that an oxidized form of BMOV readily localizes near the CTAB head-groups at the lipid-water interface. These observations were supported by IR spectroscopic studies using microemulsions of CTAB reverse micelles showing that both BMOV and oxidized BMOV are associated with the water pool. This conclusion is based on changes in (1)H NMR chemical shifts observed for the complex, oxidized BMOV. Moreover, these shifts appeared to be informative about the location of the complex. No differences were observed in the OD absorption peak positions for the CTAB reverse micelles prepared in the presence and absence of BMOV, oxidized BMOV or maltol. Combined, these results suggest that activation of IR signaling by both insulin and BMOV treatment involves increased association of IR with specialized, nanoscale membrane microdomains. The observed insulin-like activity of BMOV or decomposition products of BMOV may be due to changes in cell-surface membrane lipid order rather than due to direct interactions with IR. Read the original post:
J Cell Sci. 2012 May 4; An increasing body of evidence suggests that several membrane receptors – in addition to activating distinct signalling cascades – also engage in substantial crosstalk with each other, thereby adjusting their signalling outcome as a function of specific input information. However, little is known about the molecular mechanisms that control their coordination and integration of downstream signalling. A protein that is likely to have a role in this process is kinase-D-interacting substrate of 220 kDa [Kidins220, also known as ankyrin repeat-rich membrane spanning (ARMS), hereafter referred to as Kidins220/ARMS]. Kidins220/ARMS is a conserved membrane protein that is preferentially expressed in the nervous system and interacts with the microtubule and actin cytoskeleton. It interacts with neurotrophin, ephrin, vascular endothelial growth factor (VEGF) and glutamate receptors, and is a common downstream target of several trophic stimuli. Kidins220/ARMS is required for neuronal differentiation and survival, and its expression levels modulate synaptic plasticity. Kidins220/ARMS knockout mice show developmental defects mainly in the nervous and cardiovascular systems, suggesting a crucial role for this protein in modulating the cross talk between different signalling pathways. In this Commentary, we summarise existing knowledge regarding the physiological functions of Kidins220/ARMS, and highlight some interesting directions for future studies on the role of this protein in health and disease. Originally posted here:
World J Biol Chem. 2012 Apr 26; 3(4): 61-72 Inhibitory neurotransmission ensures normal brain function by counteracting and integrating excitatory activity. γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the mammalian central nervous system, and mediates its effects via two classes of receptors: the GABA(A) and GABA(B) receptors. GABA(A) receptors are heteropentameric GABA-gated chloride channels and responsible for fast inhibitory neurotransmission. GABA(B) receptors are heterodimeric G protein coupled receptors (GPCR) that mediate slow and prolonged inhibitory transmission. The extent of inhibitory neurotransmission is determined by a variety of factors, such as the degree of transmitter release and changes in receptor activity by posttranslational modifications (e.g., phosphorylation), as well as by the number of receptors present in the plasma membrane available for signal transduction. The level of GABA(B) receptors at the cell surface critically depends on the residence time at the cell surface and finally the rates of endocytosis and degradation. In this review we focus primarily on recent advances in the understanding of trafficking mechanisms that determine the expression level of GABA(B) receptors in the plasma membrane, and thereby signaling strength. Continued here:
World J Biol Chem. 2012 Apr 26; 3(4): 61-72 Inhibitory neurotransmission ensures normal brain function by counteracting and integrating excitatory activity. γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the mammalian central nervous system, and mediates its effects via two classes of receptors: the GABA(A) and GABA(B) receptors. GABA(A) receptors are heteropentameric GABA-gated chloride channels and responsible for fast inhibitory neurotransmission. GABA(B) receptors are heterodimeric G protein coupled receptors (GPCR) that mediate slow and prolonged inhibitory transmission. The extent of inhibitory neurotransmission is determined by a variety of factors, such as the degree of transmitter release and changes in receptor activity by posttranslational modifications (e.g., phosphorylation), as well as by the number of receptors present in the plasma membrane available for signal transduction. The level of GABA(B) receptors at the cell surface critically depends on the residence time at the cell surface and finally the rates of endocytosis and degradation. In this review we focus primarily on recent advances in the understanding of trafficking mechanisms that determine the expression level of GABA(B) receptors in the plasma membrane, and thereby signaling strength. Continued here: on trafficking of potassium channels, receptors, and membrane proteins both in vascular biology and neuroscience. This is a 3-year postdoc position funded by NIH. Please email me your CV with contact information for three references. You… Read the original here: on trafficking of potassium channels, receptors, and membrane proteins both in vascular biology and neuroscience. This is a 3-year postdoc position funded by NIH. Please email me your CV with contact information for three references. You… Read the rest here:
PLoS One. 2012; 7(4): e35709 Mechanical strain plays a critical role in the proliferation, differentiation and maturation of bone cells. As mechanical receptor cells, osteoblasts perceive and respond to stress force, such as those associated with compression, strain and shear stress. However, the underlying molecular mechanisms of this process remain unclear. Using a four-point bending device, mouse MC3T3-E1 cells was exposed to mechanical tensile strain. Cell proliferation was determined to be most efficient when stimulated once a day by mechanical strain at a frequency of 0.5 Hz and intensities of 2500 µε with once a day, and a periodicity of 1 h/day for 3 days. The applied mechanical strain resulted in the altered expression of 1992 genes, 41 of which are involved in the mitogen-activated protein kinase (MAPK) signaling pathway. Activation of ERK by mechanical strain promoted cell proliferation and inactivation of ERK by PD98059 suppressed proliferation, confirming that ERK plays an important role in the response to mechanical strain. Furthermore, the membrane-associated receptors integrin β1 and integrin β5 were determined to regulate ERK activity and the proliferation of mechanical strain-treated MC3T3-E1 cells in opposite ways. The knockdown of integrin β1 led to the inhibition of ERK activity and cell proliferation, whereas the knockdown of integrin β5 led to the enhancement of both processes. This study proposes a novel mechanism by which mechanical strain regulates bone growth and remodeling. See the original post: ISME J . 2012 Apr 26; Williams TJ, Long E, Evans F, Demaere MZ, Lauro FM, Raftery MJ, Ducklow H, Grzymski JJ, Murray AE, Cavicchioli R A metaproteomic survey of surface coastal waters near Palmer Station on the Antarctic Peninsula, West Antarctica, was performed, revealing marked differences in the functional capacity of summer and winter communities of bacterioplankton. Read the original:
Neural Plast. 2012; 2012: 261345 The proinflammatory cytokine TNFα contributes to cell death in central nervous system (CNS) disorders by altering synaptic neurotransmission. TNFα contributes to excitotoxicity by increasing GluA2-lacking AMPA receptor (AMPAR) trafficking to the neuronal plasma membrane. In vitro, increased AMPAR on the neuronal surface after TNFα exposure is associated with a rapid internalization of GABA(A) receptors (GABA(A)Rs), suggesting complex timing and dose dependency of the CNS's response to TNFα. However, the effect of TNFα on GABA(A)R trafficking in vivo remains unclear. We assessed the effect of TNFα nanoinjection on rapid GABA(A)R changes in rats (N = 30) using subcellular fractionation, quantitative western blotting, and confocal microscopy. GABA(A)R protein levels in membrane fractions of TNFα and vehicle-treated subjects were not significantly different by Western Blot, yet high-resolution quantitative confocal imaging revealed that TNFα induces GABA(A)R trafficking to synapses in a dose-dependent manner by 60 min. TNFα-mediated GABA(A)R trafficking represents a novel target for CNS excitotoxicity. Read this article:
Neural Plast. 2012; 2012: 261345 The proinflammatory cytokine TNFα contributes to cell death in central nervous system (CNS) disorders by altering synaptic neurotransmission. TNFα contributes to excitotoxicity by increasing GluA2-lacking AMPA receptor (AMPAR) trafficking to the neuronal plasma membrane. In vitro, increased AMPAR on the neuronal surface after TNFα exposure is associated with a rapid internalization of GABA(A) receptors (GABA(A)Rs), suggesting complex timing and dose dependency of the CNS's response to TNFα. However, the effect of TNFα on GABA(A)R trafficking in vivo remains unclear. We assessed the effect of TNFα nanoinjection on rapid GABA(A)R changes in rats (N = 30) using subcellular fractionation, quantitative western blotting, and confocal microscopy. GABA(A)R protein levels in membrane fractions of TNFα and vehicle-treated subjects were not significantly different by Western Blot, yet high-resolution quantitative confocal imaging revealed that TNFα induces GABA(A)R trafficking to synapses in a dose-dependent manner by 60 min. TNFα-mediated GABA(A)R trafficking represents a novel target for CNS excitotoxicity. See more here: |
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