scholarly journals Protein transport to the dendritic plasma membrane of cultured neurons is regulated by rab8p.

1993 ◽  
Vol 123 (1) ◽  
pp. 47-55 ◽  
Author(s):  
L A Huber ◽  
M J de Hoop ◽  
P Dupree ◽  
M Zerial ◽  
K Simons ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Hippocampal Neurons ◽  
Protein Transport ◽  
Semliki Forest Virus ◽  
Companion Paper ◽  
Small Gtpase ◽  
Cultured Neurons ◽  
Double Labeling ◽  
Basolateral Plasma Membrane ◽  
And Function

In the companion paper (Huber, L. A., S. W. Pimplikar, R. G. Parton, H. Virta, M. Zerial, and K. Simons. J. Cell Biol. 123:35-45) we reported that the small GTPase rab8p is involved in transport from the TGN to the basolateral plasma membrane in epithelia. In the present work we investigated the localization and function of rab8p in polarized hippocampal neurons. By immunofluorescence microscopy we found that rab8p localized preferentially in the somatodendritic domain, and was excluded from the axon. Double-labeling immunofluorescence showed that some of the rab8p co-localized in the dendrites with the Semliki Forest Virus glycoprotein E2 (SFV-E2). An antisense oligonucleotide approach was used to investigate the role of rab8p in dendritic transport of newly synthesized viral glycoproteins. Antisense oligonucleotides corresponding to the initiation region of the rab8 coding sequence were added to the cultured neurons for four days. This treatment resulted in a significant decrease in cellular levels of rab8p and transport of SFV-E2 from the cell body to the dendrites was significantly reduced. However, no effect was observed on axonal transport of influenza HA. From these results we conclude that rab8p is involved in transport of proteins to the dendritic surface in neurons.

scholarly journals Biogenesis of the Semliki Forest Virus RNA Replication Complex

2001 ◽  
Vol 75 (8) ◽  
pp. 3873-3884 ◽  
Author(s):  
Pekka Kujala ◽  
Anne Ikäheimonen ◽  
Neda Ehsani ◽  
Helena Vihinen ◽  
Petri Auvinen ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Rna Polymerase ◽  
Semliki Forest Virus ◽  
Rna Replication ◽  
Double Labeling ◽  
Virus Rna ◽  
Infected Cells ◽  
Em Autoradiography ◽  
The Individual ◽  
Alphavirus Infection

ABSTRACT The nonstructural (ns) proteins nsP1 to -4, the components of Semliki Forest virus (SFV) RNA polymerase, were localized in infected cells by confocal microscopy using double labeling with specific antisera against the individual ns proteins. All ns proteins were associated with large cytoplasmic vacuoles (CPV), the inner surfaces of which were covered by small invaginations, or spherules, typical of alphavirus infection. All ns proteins were localized by immuno-electron microscopy (EM) to the limiting membranes of CPV and to the spherules, together with newly labeled viral RNA. Along with earlier observations by EM-autoradiography (P. M. Grimley, I. K. Berezesky, and R. M. Friedman, J. Virol. 2:326–338, 1968), these results suggest that individual spherules represent template-associated RNA polymerase complexes. Immunoprecipitation of radiolabeled ns proteins showed that each antiserum precipitated the other three ns proteins, implying that they functioned as a complex. Double labeling with organelle-specific and anti-ns-protein antisera showed that CPV were derivatives of late endosomes and lysosomes. Indeed, CPV frequently contained endocytosed bovine serum albumin-coated gold particles, introduced into the medium at different times after infection. With time, increasing numbers of spherules were also observed on the cell surfaces; they were occasionally released into the medium, probably by secretory lysosomes. We suggest that the spherules arise by primary assembly of the RNA replication complexes at the plasma membrane, guided there by nsP1, which has affinity to lipids specific for the cytoplasmic leaflet of the plasma membrane. Endosomal recycling and fusion of CPV with the plasma membrane can circulate spherules between the plasma membrane and the endosomal-lysosomal compartment.

scholarly journals Density of newly synthesized plasma membrane proteins in intracellular membranes II. Biochemical studies.

1984 ◽  
Vol 98 (6) ◽  
pp. 2142-2147 ◽  
Author(s):  
P Quinn ◽  
G Griffiths ◽  
G Warren
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Membrane Proteins ◽  
Membrane Protein ◽  
Semliki Forest Virus ◽  
Companion Paper ◽  
Intracellular Membranes ◽  
Surface Areas ◽  
Quantitative Immunoblotting ◽  
Total Membrane

Using two independent methods, incorporation of radioactive amino-acid and quantitative immunoblotting, we have determined that the rate of synthesis of each of the Semliki Forest virus (SFV) proteins in infected baby hamster kidney (BHK) cells is 1.2 X 10(5) copies/cell/min. Given the absolute surface areas of the endoplasmic reticulum and Golgi complex presented in the companion paper (Griffiths, G., G. Warren, P. Quinn , O. Mathieu - Costello , and A. Hoppeler , 1984, J. Cell Biol. 98:2133-2141), and the approximate time spent in these organelles during their passage to the plasma membrane (Green J., G. Griffiths, D. Louvard , P. Quinn , and G. Warren 1981, J. Mol. Biol. 152:663-698), the mean density of each viral protein in these organelles can be calculated to be 90 and 750 molecules/micron 2 membrane, respectively. In contrast, we have determined that the density of total endogenous integral membrane proteins in these organelles is approximately 30,000 molecules/micron 2 so that the spike proteins constitute only 0.28 and 2.3% of total membrane protein in the endoplasmic reticulum and Golgi, respectively. Quantitative immunoblotting was used to give direct estimates of the concentrations of one of the viral membrane protein precursors (E1) in subcellular fractions; these agreed closely with the calculated values. The data are discussed with respect to the sorting of transported proteins from those endogenous to the intracellular membranes.

scholarly journals Septin2 mediates podosome maturation and endothelial cell invasion associated with angiogenesis

2019 ◽  
Vol 219 (2) ◽  
Author(s):  
Kerrie B. Collins ◽  
Hojin Kang ◽  
Jacob Matsche ◽  
Jennifer E. Klomp ◽  
Jalees Rehman ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Plasma Membrane ◽  
Endothelial Cell ◽  
Cell Invasion ◽  
Scaffolding Protein ◽  
Matrix Remodeling ◽  
Close Proximity ◽  
Basolateral Plasma Membrane ◽  
Binding Residues ◽  
And Function

Podosomes are compartmentalized actin-rich adhesions, defined by their ability to locally secrete proteases and remodel extracellular matrix. Matrix remodeling by endothelial podosomes facilitates invasion and thereby vessel formation. However, the mechanisms underlying endothelial podosome formation and function remain unclear. Here, we demonstrate that Septin2, Septin6, and Septin7 are required for maturation of nascent endothelial podosomes into matrix-degrading organelles. We show that podosome development occurs through initial mobilization of the scaffolding protein Tks5 and F-actin accumulation, followed by later recruitment of Septin2. Septin2 localizes around the perimeter of podosomes in close proximity to the basolateral plasma membrane, and phosphoinositide-binding residues of Septin2 are required for podosome function. Combined, our results suggest that the septin cytoskeleton forms a diffusive barrier around nascent podosomes to promote their maturation. Finally, we show that Septin2-mediated regulation of podosomes is critical for endothelial cell invasion associated with angiogenesis. Therefore, targeting of Septin2-mediated podosome formation is a potentially attractive anti-angiogenesis strategy.

scholarly journals RAB10 Interacts with ABCB4 and Regulates Its Intracellular Traffic

2021 ◽  
Vol 22 (13) ◽  
pp. 7087
Author(s):  
Amel Ben Saad ◽  
Virginie Vauthier ◽  
Martine Lapalus ◽  
Elodie Mareux ◽  
Evangéline Bennana ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Molecular Mechanisms ◽  
Significant Proportion ◽  
Deep Understanding ◽  
Small Gtpase ◽  
Membrane Expression ◽  
Intracellular Traffic ◽  
And Function ◽  
Cholestatic Diseases ◽  
Phosphatidylcholine Secretion

ABCB4 (ATP-binding cassette subfamily B member 4) is an ABC transporter expressed at the canalicular membrane of hepatocytes where it ensures phosphatidylcholine secretion into bile. Genetic variations of ABCB4 are associated with several rare cholestatic diseases. The available treatments are not efficient for a significant proportion of patients with ABCB4-related diseases and liver transplantation is often required. The development of novel therapies requires a deep understanding of the molecular mechanisms regulating ABCB4 expression, intracellular traffic, and function. Using an immunoprecipitation approach combined with mass spectrometry analyses, we have identified the small GTPase RAB10 as a novel molecular partner of ABCB4. Our results indicate that the overexpression of wild type RAB10 or its dominant-active mutant significantly increases the amount of ABCB4 at the plasma membrane expression and its phosphatidylcholine floppase function. Contrariwise, RAB10 silencing induces the intracellular retention of ABCB4 and then indirectly diminishes its secretory function. Taken together, our findings suggest that RAB10 regulates the plasma membrane targeting of ABCB4 and consequently its capacity to mediate phosphatidylcholine secretion.

Bilitranslocase localization and function in basolateral plasma membrane of renal proximal tubule in rat

1990 ◽  
Vol 259 (4) ◽  
pp. F559-F564 ◽  
Author(s):  
M. M. Elias ◽  
G. C. Lunazzi ◽  
S. Passamonti ◽  
B. Gazzin ◽  
M. Miccio ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Competitive Inhibition ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Order Of Magnitude ◽  
Single Positive ◽  
Basolateral Plasma Membrane ◽  
Renal Tubular ◽  
And Function ◽  
Monospecific Antibodies

Bilirubin and phthalein dyes are taken up by the liver via a carrier-mediated mechanism operated at least in part by bilitranslocase (BTL). Because they also undergo renal transport, the presence and function of BTL was investigated in rat renal tubular plasma membrane vesicles. Transport of sulfobromophthalein (BSP) was enriched in basolateral domain of plasma membrane and followed the distribution pattern of Na(+)-K(+)-ATPase but not of gamma-glutamyltransferase. BSP uptake was inhibited by addition of monospecific antibodies raised against hepatic BTL. As in liver vesicles, BSP transport was electrogenic, being greatly accelerated by addition of valinomycin in presence of an inwardly directed K+ gradient. Apparent Km of BSP transport was 17 +/- 2 microM (n = 3 expts), one order of magnitude higher than that measured in liver; however, Vmax was similar to that described in liver vesicles (429 +/- 18 nmol BSP.mg protein-1.min-1, n = 3 expts). Competitive inhibition was observed with both unconjugated bilirubin (Ki, 2.9 +/- 0.2 microM) and rifamycin SV (Ki, 76 +/- 10 microM), known competitors for hepatic BTL-mediated transport of BSP. Immunoblotting studies with anti-BTL monospecific antibodies revealed presence of a single positive band only in basolateral-enriched membrane fraction; its apparent molecular mass was 37 kDa, virtually identical to that of hepatic protein. Immunohistochemistry confined presence of BTL to renal proximal tubules (RPT) We conclude that BTL is present in basolateral plasma membrane of RPT cells. Lower affinity of renal, compared with hepatic protein, for substrates might explain the marginal role of kidney in plasma clearance of bilirubin and cholephilic dyes.

scholarly journals Role of the Second Cysteine-rich Domain and Pro275 in Protein Kinase D2 Interaction with ADP-Ribosylation Factor 1, Trans-Golgi Network Recruitment, and Protein Transport

2010 ◽  
Vol 21 (6) ◽  
pp. 1011-1022 ◽  
Author(s):  
Ganesh Varma Pusapati ◽  
Denis Krndija ◽  
Milena Armacki ◽  
Götz von Wichert ◽  
Julia von Blume ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase ◽  
Protein Transport ◽  
Small Gtpase ◽  
Adp Ribosylation ◽  
Trans Golgi Network ◽  
Rich Domain ◽  
Golgi Network ◽  
Adp Ribosylation Factor ◽  
Cysteine Rich Domain

Protein kinase D (PKD) isoenzymes regulate the formation of transport carriers from the trans-Golgi network (TGN) that are en route to the plasma membrane. The PKD C1a domain is required for the localization of PKDs at the TGN. However, the precise mechanism of how PKDs are recruited to the TGN is still elusive. Here, we report that ADP-ribosylation factor (ARF1), a small GTPase of the Ras superfamily and a key regulator of secretory traffic, specifically interacts with PKD isoenzymes. ARF1, but not ARF6, binds directly to the second cysteine-rich domain (C1b) of PKD2, and precisely to Pro275 within this domain. Pro275 in PKD2 is not only crucial for the PKD2-ARF1 interaction but also for PKD2 recruitment to and PKD2 function at the TGN, namely, protein transport to the plasma membrane. Our data suggest a novel model in which ARF1 recruits PKD2 to the TGN by binding to Pro275 in its C1b domain followed by anchoring of PKD2 in the TGN membranes via binding of its C1a domain to diacylglycerol. Both processes are critical for PKD2-mediated protein transport.

scholarly journals Lst1p and Sec24p Cooperate in Sorting of the Plasma Membrane Atpase into Copii Vesicles in Saccharomyces cerevisiae

2000 ◽  
Vol 151 (5) ◽  
pp. 973-984 ◽  
Author(s):  
Yuval Shimoni ◽  
Tatsuo Kurihara ◽  
Mariella Ravazzola ◽  
Mylène Amherdt ◽  
Lelio Orci ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Plasma Membrane ◽  
Protein Transport ◽  
Buoyant Density ◽  
Small Gtpase ◽  
Plasma Membrane Atpase ◽  
Vesicle Budding ◽  
Transport Vesicles ◽  
Membrane Atpase ◽  
Copii Vesicles

Formation of ER-derived protein transport vesicles requires three cytosolic components, a small GTPase, Sar1p, and two heterodimeric complexes, Sec23/24p and Sec13/31p, which comprise the COPII coat. We investigated the role of Lst1p, a Sec24p homologue, in cargo recruitment into COPII vesicles in Saccharomyces cerevisiae. A tagged version of Lst1p was purified and eluted as a heterodimer complexed with Sec23p comparable to the Sec23/24p heterodimer. We found that cytosol from an lst1-null strain supported the packaging of α-factor precursor into COPII vesicles but was deficient in the packaging of Pma1p, the essential plasma membrane ATPase. Supplementation of mutant cytosol with purified Sec23/Lst1p restored Pma1p packaging into the vesicles. When purified COPII components were used in the vesicle budding reaction, Pma1p packaging was optimal with a mixture of Sec23/24p and Sec23/Lst1p; Sec23/Lst1p did not replace Sec23/24p. Furthermore, Pma1p coimmunoprecipitated with Lst1p and Sec24p from vesicles. Vesicles formed with a mixture of Sec23/Lst1p and Sec23/24p were similar morphologically and in their buoyant density, but larger than normal COPII vesicles (87-nm vs. 75-nm diameter). Immunoelectronmicroscopic and biochemical studies revealed both Sec23/Lst1p and Sec23/24p on the membranes of the same vesicles. These results suggest that Lst1p and Sec24p cooperate in the packaging of Pma1p and support the view that biosynthetic precursors of plasma membrane proteins must be sorted into ER-derived transport vesicles. Sec24p homologues may comprise a more complex coat whose combinatorial subunit composition serves to expand the range of cargo to be packaged into COPII vesicles. By changing the geometry of COPII coat polymerization, Lst1p may allow the transport of bulky cargo molecules, polymers, or particles.

scholarly journals Analysis of NIS Plasma Membrane Interactors Discloses Key Regulation by a SRC/RAC1/PAK1/PIP5K/EZRIN Pathway with Potential Implications for Radioiodine Re-Sensitization Therapy in Thyroid Cancer

Cancers ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 5460
Author(s):  
Márcia Faria ◽  
Rita Domingues ◽  
Maria João Bugalho ◽  
Ana Luísa Silva ◽  
Paulo Matos
Keyword(s):  
Plasma Membrane ◽  
Thyroid Cancer ◽  
Actin Polymerization ◽  
Functional Characterization ◽  
Thyroid Tissue ◽  
Small Gtpase ◽  
Mrna Levels ◽  
Iodide Uptake ◽  
Thyroid Cells ◽  
And Function

The functional expression of the sodium–iodide symporter (NIS) at the membrane of differentiated thyroid cancer (DTC) cells is the cornerstone for the use of radioiodine (RAI) therapy in these malignancies. However, NIS gene expression is frequently downregulated in malignant thyroid tissue, and 30% to 50% of metastatic DTCs become refractory to RAI treatment, which dramatically decreases patient survival. Several strategies have been attempted to increase the NIS mRNA levels in refractory DTC cells, so as to re-sensitize refractory tumors to RAI. However, there are many RAI-refractory DTCs in which the NIS mRNA and protein levels are relatively abundant but only reduced levels of iodide uptake are detected, suggesting a posttranslational failure in the delivery of NIS to the plasma membrane (PM), or an impaired residency at the PM. Because little is known about the molecules and pathways regulating NIS delivery to, and residency at, the PM of thyroid cells, we here employed an intact-cell labeling/immunoprecipitation methodology to selectively purify NIS-containing macromolecular complexes from the PM. Using mass spectrometry, we characterized and compared the composition of NIS PM complexes to that of NIS complexes isolated from whole cell (WC) lysates. Applying gene ontology analysis to the obtained MS data, we found that while both the PM-NIS and WC-NIS datasets had in common a considerable number of proteins involved in vesicle transport and protein trafficking, the NIS PM complexes were particularly enriched in proteins associated with the regulation of the actin cytoskeleton. Through a systematic validation of the detected interactions by co-immunoprecipitation and Western blot, followed by the biochemical and functional characterization of the contribution of each interactor to NIS PM residency and iodide uptake, we were able to identify a pathway by which the PM localization and function of NIS depends on its binding to SRC kinase, which leads to the recruitment and activation of the small GTPase RAC1. RAC1 signals through PAK1 and PIP5K to promote ARP2/3-mediated actin polymerization, and the recruitment and binding of the actin anchoring protein EZRIN to NIS, promoting its residency and function at the PM of normal and TC cells. Besides providing novel insights into the regulation of NIS localization and function at the PM of TC cells, our results open new venues for therapeutic intervention in TC, namely the possibility of modulating abnormal SRC signaling in refractory TC from a proliferative/invasive effect to the re-sensitization of these tumors to RAI therapy by inducing NIS retention at the PM.

scholarly journals The Nucleolar δ Isoform of Adapter Protein SH2B1 Enhances Morphological Complexity and Function of Cultured Neurons

2022 ◽  
Author(s):  
Jessica L. Cote ◽  
Paul B. Vander ◽  
Michael Ellis ◽  
Joel M. Cline ◽  
Nadezhda Svezhova ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Hippocampal Neurons ◽  
Adapter Protein ◽  
Neurotrophin Receptors ◽  
Neurite Length ◽  
Human Obesity ◽  
Induced Expression ◽  
Alternatively Spliced ◽  
And Function ◽  
The Brain

The adapter protein SH2B1 is recruited to neurotrophin receptors including TrkB, receptor for brain-derived neurotrophic factor (BDNF). Herein, we demonstrate that the four alternatively spliced isoforms of SH2B1 are important determinants of neuronal architecture and neurotrophin-induced gene expression. Primary hippocampal neurons from Sh2b1−/- (KO) mice exhibit decreased neurite complexity and length and BDNF-induced expression of synapse-related immediate early genes Egr1 and Arc. Reintroduction of each SH2B1 isoform into KO neurons increases neurite complexity; the brain-specific δ isoform also increases total neurite length. Human obesity-associated variants, when expressed in SH2B1δ, alter neurite complexity, suggesting that a decrease or increase in neurite branching may have deleterious effects that contribute to the severe childhood obesity and neurobehavioral abnormalities associated with these variants. Surprisingly, in contrast to SH2B1α, β, and γ, which localize primarily in the cytoplasm and plasma membrane, SH2B1δ localizes primarily in nucleoli. Some SH2B1δ is also present in the plasma membrane and nucleus. Nucleolar localization, driven by two highly basic regions unique to SH2B1δ, is required for SH2B1δ to maximally increase neurite complexity and BDNF-induced expression of Egr1, Arc, and FosL1.

scholarly journals The adhesion-GPCR BAI1 shapes dendritic arbors via Bcr-mediated RhoA activation causing late growth arrest

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Joseph G Duman ◽  
Shalaka Mulherkar ◽  
Yen-Kuei Tu ◽  
Kelly C Erikson ◽  
Christopher P Tzeng ◽  
...  
Keyword(s):  
Hippocampal Neurons ◽  
Rho Gtpase ◽  
Regulatory Protein ◽  
Growth Arrest ◽  
Dendritic Morphology ◽  
Small Gtpase ◽  
Rhoa Activation ◽  
Dependent Growth ◽  
And Function ◽  
Adhesion Gpcr

Dendritic arbor architecture profoundly impacts neuronal connectivity and function, and aberrant dendritic morphology characterizes neuropsychiatric disorders. Here, we identify the adhesion-GPCR BAI1 as an important regulator of dendritic arborization. BAI1 loss from mouse or rat hippocampal neurons causes dendritic hypertrophy, whereas BAI1 overexpression precipitates dendrite retraction. These defects specifically manifest as dendrites transition from growth to stability. BAI1-mediated growth arrest is independent of its Rac1-dependent synaptogenic function. Instead, BAI1 couples to the small GTPase RhoA, driving late RhoA activation in dendrites coincident with growth arrest. BAI1 loss lowers RhoA activation and uncouples it from dendrite dynamics, causing overgrowth. None of BAI1’s known downstream effectors mediates BAI1-dependent growth arrest. Rather, BAI1 associates with the Rho-GTPase regulatory protein Bcr late in development and stimulates its cryptic RhoA-GEF activity, which functions together with its Rac1-GAP activity to terminate arborization. Our results reveal a late-acting signaling pathway mediating a key transition in dendrite development.

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