|
|
By admin, on May 16th, 2012
J Neurosci. 2012 May 9; 32(19): 6587-6599
Takano T, Tomomura M, Yoshioka N, Tsutsumi K, Terasawa Y, Saito T, Kawano H, Kamiguchi H, Fukuda M, Hisanaga SI
Axonal outgrowth is a coordinated process of cytoskeletal dynamics and membrane trafficking; however, little is known about proteins responsible for regulating the membrane supply. LMTK1 (lemur kinase 1)/AATYK1 (apoptosis-associated tyrosine kinase 1) is a serine/threonine kinase that is highly expressed in neurons. We recently reported that LMTK1 plays a role in recycling endosomal trafficking in CHO-K1 cells. Here we explore the role of LMTK1 in axonal outgrowth and its regulation by Cdk5 using mouse brain cortical neurons. LMTK1 was expressed and was phosphorylated at Ser34, the Cdk5 phosphorylation site, at the time of axonal outgrowth in culture and colocalized with Rab11A, the small GTPase that regulates recycling endosome traffic, at the perinuclear region and in the axon. Overexpression of the unphosphorylated mutant LMTK1-S34A dramatically promoted axonal outgrowth in cultured neurons. Enhanced axonal outgrowth was diminished by the inactivation of Rab11A, placing LMTK1 upstream of Rab11A. Unexpectedly, the downregulation of LMTK1 by knockdown or gene targeting also significantly enhanced axonal elongation. Rab11A-positive vesicles were transported anterogradely more quickly in the axons of LMTK1-deficient neurons than in those of wild-type neurons. The enhanced axonal outgrowth was reversed by LMTK1-WT or the LMTK1-S34D mutant, which mimics the phosphorylated state, but not by LMTK1-S34A. Thus, LMTK1 can negatively control axonal outgrowth by regulating Rab11A activity in a Cdk5-dependent manner, and Cdk5-LMTK1-Rab11 is a novel signaling pathway involved in axonal outgrowth.
The rest is here:
LMTK1/AATYK1 Is a Novel Regulator of Axonal Outgrowth That Acts via Rab11 in a Cdk5-Dependent Manner.
By admin, on May 8th, 2012
World J Biol Chem. 2012 Apr 26; 3(4): 61-72
Benke D, Zemoura K, Maier PJ
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:
Modulation of cell surface GABA(B) receptors by desensitization, trafficking and regulated degradation.
By admin, on May 5th, 2012
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:
Postdoctoral Fellow at University of South Alabama College of Medicine (Alabama)
By admin, on May 5th, 2012
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:
Postdoctoral Fellow at University of South Alabama College of Medicine (Alabama)
By admin, on April 25th, 2012
Neural Plast. 2012; 2012: 261345
Stück ED, Christensen RN, Huie JR, Tovar CA, Miller BA, Nout YS, Bresnahan JC, Beattie MS, Ferguson AR
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:
Tumor Necrosis Factor Alpha Mediates GABA(A) Receptor Trafficking to the Plasma Membrane of Spinal Cord Neurons In Vivo.
By admin, on April 19th, 2012
Neuro Oncol. 2012 Apr 16;
Parat MO, Riggins GJ
Glioblastoma multiforme (GBM) is the most common malignant brain tumor and is characterized by high invasiveness, poor prognosis, and limited therapeutic options. Biochemical and morphological experiments have shown the presence of caveolae in glioblastoma cells. Caveolae are flask-shaped plasma membrane subdomains that play trafficking, mechanosensing, and signaling roles. Caveolin-1 is a membrane protein that participates in the formation of caveolae and binds a multitude of signaling proteins, compartmentalizing them in caveolae and often directly regulating their activity via binding to its scaffolding domain. Caveolin-1 has been proposed to behave either as a tumor suppressor or as an ongogene depending on the tumor type and progress. This review discusses the existing information on the expression and function of caveolin-1 and caveolae in GBM and the role of this organelle and its defining protein on cellular signaling, growth, and invasiveness of GBM. We further analyze the available data suggesting caveolin-1 could be a target in GBM therapy.
Read more:
Caveolin-1, caveolae, and glioblastoma.
By admin, on March 29th, 2012
Adv Exp Med Biol. 2012; 740: 439-60
Micaroni M
As with other complex cellular functions, intracellular membrane transport involves the coordinated engagement of a series of organelles and machineries; in the last couple of decades more importance has been given to the role of calcium (Ca(2+)) in the regulation of membrane trafficking, which is directly involved in coordinating the endoplasmic reticulum-to-Golgi-to-plasma membrane delivery of cargo. Consequently, the Golgi apparatus (GA) is now considered not just the place proteins mature in as they move to their final destination(s), but it is increasingly viewed as an intracellular Ca(2+) store. In the last few years the mechanisms regulating the homeostasis of Ca(2+) in the GA and its role in membrane trafficking have begun to be elucidated. Here, these recent discoveries that shed light on the role Ca(2+) plays as of trigger of different steps during membrane trafficking has been reviewed. This includes recruitment of proteins and SNARE cofactors to the Golgi membranes, which are both fundamental for the membrane remodeling and the regulation of fusion/fission events occurring during the passage of cargo across the GA. I conclude by focusing attention on Ca(2+) homeostasis dysfunctions in the GA and their related pathological implications.
Read more here:
Calcium around the Golgi apparatus: implications for intracellular membrane trafficking.
By admin, on March 29th, 2012
Adv Exp Med Biol. 2012; 740: 439-60
Micaroni M
As with other complex cellular functions, intracellular membrane transport involves the coordinated engagement of a series of organelles and machineries; in the last couple of decades more importance has been given to the role of calcium (Ca(2+)) in the regulation of membrane trafficking, which is directly involved in coordinating the endoplasmic reticulum-to-Golgi-to-plasma membrane delivery of cargo. Consequently, the Golgi apparatus (GA) is now considered not just the place proteins mature in as they move to their final destination(s), but it is increasingly viewed as an intracellular Ca(2+) store. In the last few years the mechanisms regulating the homeostasis of Ca(2+) in the GA and its role in membrane trafficking have begun to be elucidated. Here, these recent discoveries that shed light on the role Ca(2+) plays as of trigger of different steps during membrane trafficking has been reviewed. This includes recruitment of proteins and SNARE cofactors to the Golgi membranes, which are both fundamental for the membrane remodeling and the regulation of fusion/fission events occurring during the passage of cargo across the GA. I conclude by focusing attention on Ca(2+) homeostasis dysfunctions in the GA and their related pathological implications.
Originally posted here:
Calcium around the Golgi apparatus: implications for intracellular membrane trafficking.
By admin, on March 29th, 2012
Traffic. 2012 Mar 23;
Shi G, Azoulay M, Dingli F, Lamaze C, Loew D, Florent JC, Johannes L
Proteomics is a powerful technique for protein identification at large scales. A number of proteomics approaches have been developed to study the steady state composition of intracellular compartments. Here, we report a novel vectorial proteomics strategy to identify plasma membrane proteins that undergo retrograde transport to the trans-Golgi network. This strategy is based on the covalent modification of the plasma membrane proteome with a membrane impermeable benzylguanine derivative. Benzylguanine-tagged plasma membrane proteins that are subsequently targeted to the retrograde route are covalently captured by a TGN-localized SNAP-tagged fusion protein, which allows for their identification. The approach was validated step-by-step using a well explored retrograde cargo protein, the B-subunit of Shiga toxin. It was then extended to the proteomics format. Amongst other hits we found one of the historically first identified cargo proteins that undergo retrograde transport, which further validated our approach. Most of the other hits are kinases, receptors or transporters. In conclusion, we have pioneered a vectorial proteomics approach that complements traditional methods for the study of retrograde protein trafficking. This approach is of generic nature and could in principle be extended to other endocytic pathways.
Go here to see the original:
SNAP-tag based proteomics approach for the study of the retrograde route.
By admin, on March 27th, 2012
Commun Integr Biol. 2011 Nov 1; 4(6): 703-5
Wu C, Horowitz A
The change in the overall shape of developing organs is a consequence of the cumulative movement, reshaping, and proliferation of the individual mural cells that make up the walls of these organs. Recent observations suggest that the shape and the position of endothelial cells (ECs) in growing blood vessels are highly dynamic, implying that these cells remodel their junctions extensively and do not preserve their initial relative positions. In order to determine the mechanisms that confer the dynamic behavior of mural ECs, we tracked the trafficking of a cell junction protein complex that consists of the RhoA-specific guanine exchange factor (GEF) Syx, the scaffold protein Mupp1, and the phospholipid binding protein Amot.1 We found that RhoA co-trafficked with this complex on the same endocytic vesicles, and that its cellular activity pattern was determined by Rab13-dependent trafficking. The vesicles were targeted by a Rab13-associated protein complex to Tyr(1175)-phosphorylated VEGFR2 at the leading edge of ECs migrating under a VEGF gradient. These results indicate that the dynamic behavior of ECs in sprouting vessels is conferred by using the same protein complex for the regulation of both cell junctions and cell motility. Together with previous studies that demonstrated regulation of Rac signaling by Rab5-dependent trafficking,(2) it appears now that membrane traffic is tightly coupled to the regulation of Rho GTPases, and, consequently, to the regulation of the actin cytoskeleton, cell junctions, and cell migration.
Read more:
Membrane traffic as a coordinator of cell migration and junction remodeling.
By admin, on March 27th, 2012
Biochim Biophys Acta. 2012 Mar 14;
Tang L, Fares H, Zhao X, Du W, Liu BF
BACKGROUND: ADP-ribosylation factors (ARFs) are a family of small GTP-binding proteins that play roles in membrane dynamics and vesicle trafficking. AGEF-1, which is thought to act as a guanine nucleotide exchange factor of class I ARFs, is required for caveolin-1 body formation and receptor-mediated endocytosis in oocytes of Caenorhabditis elegans. This study explores additional roles of AGEF-1 in endocytic transport. METHODS: agef-1 expression was knocked down by using RNAi in C. elegans. Markers that allow analysis of endocytic transport in scavenger cells were investigated for studying the effect of AGEF-1 on different steps of membrane transport. RESULTS: Knockdown of AGEF-1 levels results in two apparent trafficking defects in coelomocytes of C. elegans. First, there is a delay in the uptake of solutes from the extracellular medium. Second, there is a dramatic enlargement of the sizes of lysosomes, even though lysosomal acidification is normal and degradation still occurs. CONCLUSION: Our results suggest that AGEF-1 regulates endosome/lysosome fusion or fission events, in addition to earlier steps in endocytic transport. GENERAL SIGNIFICANCE: AGEF-1 is the first identified GTPase regulator that functions at the lysosome fusion or fission stage of the endocytic pathway. Our study provides insight into lysosome dynamics in C. elegans.
Go here to read the rest:
Different endocytic functions of AGEF-1 in C. elegans coelomocytes.
By admin, on March 23rd, 2012
PLoS Genet. 2012 Mar; 8(3): e1002568
Olszewski PK, Rozman J, Jacobsson JA, Rathkolb B, Strömberg S, Hans W, Klockars A, Alsiö J, Risérus U, Becker L, Hölter SM, Elvert R, Ehrhardt N, Gailus-Durner V, Fuchs H, Fredriksson R, Wolf E, Klopstock T, Wurst W, Levine AS, Marcus C, Hrabě de Angelis M, Klingenspor M, Schiöth HB, Kilimann MW
Neurobeachin (Nbea) regulates neuronal membrane protein trafficking and is required for the development and functioning of central and neuromuscular synapses. In homozygous knockout (KO) mice, Nbea deficiency causes perinatal death. Here, we report that heterozygous KO mice haploinsufficient for Nbea have higher body weight due to increased adipose tissue mass. In several feeding paradigms, heterozygous KO mice consumed more food than wild-type (WT) controls, and this consumption was primarily driven by calories rather than palatability. Expression analysis of feeding-related genes in the hypothalamus and brainstem with real-time PCR showed differential expression of a subset of neuropeptide or neuropeptide receptor mRNAs between WT and Nbea+/- mice in the sated state and in response to food deprivation, but not to feeding reward. In humans, we identified two intronic NBEA single-nucleotide polymorphisms (SNPs) that are significantly associated with body-mass index (BMI) in adult and juvenile cohorts. Overall, data obtained in mice and humans suggest that variation of Nbea abundance or activity critically affects body weight, presumably by influencing the activity of feeding-related neural circuits. Our study emphasizes the importance of neural mechanisms in body weight control and points out NBEA as a potential risk gene in human obesity.
Go here to see the original:
Neurobeachin, a regulator of synaptic protein targeting, is associated with body fat mass and feeding behavior in mice and body-mass index in humans.
By admin, on March 23rd, 2012
PLoS Genet. 2012 Mar; 8(3): e1002568
Olszewski PK, Rozman J, Jacobsson JA, Rathkolb B, Strömberg S, Hans W, Klockars A, Alsiö J, Risérus U, Becker L, Hölter SM, Elvert R, Ehrhardt N, Gailus-Durner V, Fuchs H, Fredriksson R, Wolf E, Klopstock T, Wurst W, Levine AS, Marcus C, Hrabě de Angelis M, Klingenspor M, Schiöth HB, Kilimann MW
Neurobeachin (Nbea) regulates neuronal membrane protein trafficking and is required for the development and functioning of central and neuromuscular synapses. In homozygous knockout (KO) mice, Nbea deficiency causes perinatal death. Here, we report that heterozygous KO mice haploinsufficient for Nbea have higher body weight due to increased adipose tissue mass. In several feeding paradigms, heterozygous KO mice consumed more food than wild-type (WT) controls, and this consumption was primarily driven by calories rather than palatability. Expression analysis of feeding-related genes in the hypothalamus and brainstem with real-time PCR showed differential expression of a subset of neuropeptide or neuropeptide receptor mRNAs between WT and Nbea+/- mice in the sated state and in response to food deprivation, but not to feeding reward. In humans, we identified two intronic NBEA single-nucleotide polymorphisms (SNPs) that are significantly associated with body-mass index (BMI) in adult and juvenile cohorts. Overall, data obtained in mice and humans suggest that variation of Nbea abundance or activity critically affects body weight, presumably by influencing the activity of feeding-related neural circuits. Our study emphasizes the importance of neural mechanisms in body weight control and points out NBEA as a potential risk gene in human obesity.
Read the rest here:
Neurobeachin, a regulator of synaptic protein targeting, is associated with body fat mass and feeding behavior in mice and body-mass index in humans.
By admin, on March 23rd, 2012
Biochem Soc Trans. 2012 Apr 1; 40(2): 451-6
Cockcroft S, Garner K
PITPs (phosphatidylinositol transfer proteins) are characterized by the presence of the PITP domain whose biochemical properties of binding and transferring PI (phosphatidylinositol) are well studied. Despite their wide-spread expression in both unicellular and multicellular organisms, they remain functionally uncharacterized. An emerging theme is that individual PITPs play highly specific roles in either membrane trafficking or signal transduction. To identify specific roles for PITPs, identification of interacting molecules would shed light on their molecular function. In the present paper, we describe binding partners for the class IIB PITP RdgBβ (retinal degeneration type Bβ). RdgBβ is a soluble PITP but is unique in that it contains a region of disorder at its C-terminus following its defining N-terminal PITP domain. The C-terminus of RdgBβ is phosphorylated at two serine residues, Ser274 and Ser299, which form a docking site for 14-3-3 proteins. Binding to 14-3-3 proteins protects RdgBβ from degradation that occurs at the proteasome after ubiquitination. In addition to binding 14-3-3, the PITP domain of RdgBβ interacts with the Ang II (angiotensin II)-associated protein ATRAP (Ang II receptor-associated protein). ATRAP is also an interacting partner for the AT1R (Ang II type 1 receptor). We present a model whereby RdgBβ functions by being recruited to the membrane by ATRAP and release of 14-3-3 from the C-terminus allows the disordered region to bind a second membrane to create a membrane bridge for lipid transfer, possibly under the control of Ang II.
View post:
14-3-3 protein and ATRAP bind to the soluble class IIB phosphatidylinositol transfer protein RdgBβ at distinct sites.
By admin, on March 13th, 2012
Biochim Biophys Acta . 2012 Mar 1; Duncan O, Murcha MW, Whelan J The basic mitochondrial protein import apparatus was established in the earliest eukaryotes.
See original here:
Unique components of the plant mitochondrial protein import apparatus.
By admin, on March 11th, 2012
|
