scholarly journals Insights into Cell Surface Expression, Supramolecular Organization, and Functions of Aquaporin 4 Isoforms in Astrocytes

Cells ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 2622
Author(s):  
Jernej Jorgačevski ◽  
Robert Zorec ◽  
Maja Potokar
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Water Channel ◽  
Surface Expression ◽  
Extracellular Proteins ◽  
Aquaporin 4 ◽  
Cell Surface Expression ◽  
Supramolecular Organization ◽  
Surface Distribution ◽  
Orthogonal Arrays Of Particles

Aquaporin 4 (AQP4) is the most abundant water channel in the central nervous system (CNS). Its expression is confined to non-neuronal glial cells, predominantly to astrocytes that represent a heterogeneous glial cell type in the CNS. The membrane of astrocyte processes, which align brain capillaries and pia, is particularly rich in AQP4. Several isoforms of AQP4 have been described; however, only some (AQP4a (M1), AQP4 c (M23), AQP4e, and AQP4ex) have been identified in the plasma membrane assemblies of astrocytes termed orthogonal arrays of particles (OAPs). Intracellular splicing isoforms (AQP4b, AQP4d, AQP4f, AQP4-Δ4) have been documented, and most of them are postulated to have a role in the cell surface distribution of the plasma membrane isoforms and in the formation of OAPs in murine and human astrocytes. Although OAPs have been proposed to play various roles in the functioning of astrocytes and CNS tissue as a whole, many of these still need to be described. OAPs are studied primarily from the perspective of understanding water permeability regulation through the plasma membrane and of their involvement in cell adhesion and in the dynamics of astrocytic processes. This review describes the cellular distribution of various AQP4 isoforms and their implications in OAP assembly, which is regulated by several intracellular and extracellular proteins.

Effect of aging on CD11b and CD69 surface expression by vesicular insertion in human polymorphonuclear leucocytes

1999 ◽  
Vol 97 (3) ◽  
pp. 323-329 ◽  
Author(s):  
J. M. NOBLE ◽  
G. A. FORD ◽  
T. H. THOMAS
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Surface Expression ◽  
Cell Surface Receptor ◽  
Cell Surface Expression ◽  
Elderly Subjects ◽  
Polymorphonuclear Leucocytes ◽  
Cd11b Expression ◽  
Cd69 Expression ◽  
Vesicle Exocytosis

The exocytosis of intracellular vesicles is an important function of the plasma membrane, which is responsible for hormone secretion, cell surface expression of antigens, ion transporters and receptors, and intracellular and intercellular signalling. Human aging is associated with many physiological and cellular changes, many of which are due to alterations in plasma membrane functioning. Alterations in vesicle externalization with age could account for many of these changes. We investigated whether alterations in vesicle exocytosis occur with increasing age by flow-cytometric determination of CD11b and CD69 expression on the surface of human polymorphonuclear leucocytes (PMN) stimulated with phorbol myristate acetate (PMA), a tumour promoter which binds to and activates protein kinase C (PKC) directly, or with formyl-Met-Leu-Phe (fMLP), which activates PKC indirectly via interactions with a cell surface receptor and G-protein, and subsequent inositol phosphate hydrolysis. Following stimulation with PMA, a decrease in the proportion of PMN expressing CD69 at high levels was observed in elderly compared with young subjects (young, 55.3%; elderly, 43.9%; P = 0.01). No aging-related differences in the proportion of PMN expressing CD11b (young, 73.7%; elderly, 68.4%; P = 0.15), or in the number of molecules of CD69 or CD11b expressed per cell, were observed. Stimulation with fMLP or low PMA concentrations resulted in full CD11b expression but minimal CD69 expression in both young and elderly subjects. Cells which expressed CD69 had no CD11b expression, while those cells expressing CD11b had minimal CD69 expression. Thus the PMA-induced expression of CD11b and CD69 in human PMN represents two separate processes, only one of which is affected in aging. CD11b expression appears to require a lesser degree of PKC stimulation compared with that required for CD69 expression. The age-associated reduction in PMA-stimulated CD69 expression may occur either at or distal to PKC activation. Such a decrease may contribute to the age-associated impairments in PMN function that contribute, in turn, to immunosenescence.

scholarly journals GLUT8 Subcellular Localization and Absence of Translocation to the Plasma Membrane in PC12 Cells and Hippocampal Neurons

Endocrinology ◽  
2005 ◽  
Vol 146 (11) ◽  
pp. 4727-4736 ◽  
Author(s):  
Mathieu Widmer ◽  
Marc Uldry ◽  
Bernard Thorens
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase ◽  
Cell Surface ◽  
Pc12 Cells ◽  
Hippocampal Neurons ◽  
Osmotic Shock ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Intracellular Compartment ◽  
Early Endosomes

GLUT8 is a high-affinity glucose transporter present mostly in testes and a subset of brain neurons. At the cellular level, it is found in a poorly defined intracellular compartment in which it is retained by an N-terminal dileucine motif. Here we assessed GLUT8 colocalization with markers for different cellular compartments and searched for signals, which could trigger its cell surface expression. We showed that when expressed in PC12 cells, GLUT8 was located in a perinuclear compartment in which it showed partial colocalization with markers for the endoplasmic reticulum but not with markers for the trans-Golgi network, early endosomes, lysosomes, and synaptic-like vesicles. To evaluate its presence at the plasma membrane, we generated a recombinant adenovirus for the expression of GLUT8 containing an extracellular myc epitope. Cell surface expression was evaluated by immunofluorescence microscopy of transduced PC12 cells or primary hippocampal neurons exposed to different stimuli. Those included substances inducing depolarization, activation of protein kinase A and C, activation or inhibition of tyrosine kinase-linked signaling pathways, glucose deprivation, AMP-activated protein kinase stimulation, and osmotic shock. None of these stimuli-induced GLUT8 cell surface translocation. Furthermore, when GLUT8myc was cotransduced with a dominant-negative form of dynamin or GLUT8myc-expressing PC-12 cells or neurons were incubated with an anti-myc antibody, no evidence for constitutive recycling of the transporter through the cell surface could be obtained. Thus, in cells normally expressing it, GLUT8 was associated with a specific intracellular compartment in which it may play an as-yet-uncharacterized role.

scholarly journals A novel human aquaporin-4 splice variant exhibits a dominant-negative activity: a new mechanism to regulate water permeability

2014 ◽  
Vol 25 (4) ◽  
pp. 470-480 ◽  
Author(s):  
Manuela De Bellis ◽  
Francesco Pisani ◽  
Maria Grazia Mola ◽  
Davide Basco ◽  
Francesco Catalano ◽  
...  
Keyword(s):  
Water Transport ◽  
Skeletal Muscles ◽  
Water Channel ◽  
Surface Expression ◽  
Dominant Negative ◽  
Aquaporin 4 ◽  
Cell Surface Expression ◽  
Dominant Negative Effect ◽  
Negative Effect ◽  
Dominant Negative Activity

Two major isoforms of aquaporin-4 (AQP4) have been described in human tissue. Here we report the identification and functional analysis of an alternatively spliced transcript of human AQP4, AQP4-Δ4, that lacks exon 4. In transfected cells AQP4-Δ4 is mainly retained in the endoplasmic reticulum and shows no water transport properties. When AQP4-Δ4 is transfected into cells stably expressing functional AQP4, the surface expression of the full-length protein is reduced. Furthermore, the water transport activity of the cotransfectants is diminished in comparison to transfectants expressing only AQP4. The observed down-regulation of both the expression and water channel activity of AQP4 is likely to originate from a dominant-negative effect caused by heterodimerization between AQP4 and AQP4-Δ4, which was detected in coimmunoprecipitation studies. In skeletal muscles, AQP4-Δ4 mRNA expression inversely correlates with the level of AQP4 protein and is physiologically associated with different types of skeletal muscles. The expression of AQP4-Δ4 may represent a new regulatory mechanism through which the cell-surface expression and therefore the activity of AQP4 can be physiologically modulated.

scholarly journals Intracellular Retention of Glycosylphosphatidyl Inositol-Linked Proteins in Caveolin-Deficient Cells

2002 ◽  
Vol 22 (11) ◽  
pp. 3905-3926 ◽  
Author(s):  
Federica Sotgia ◽  
Babak Razani ◽  
Gloria Bonuccelli ◽  
William Schubert ◽  
Michela Battista ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Lipid Rafts ◽  
Recombinant Expression ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Null Mouse ◽  
Tissue Samples ◽  
Caveolin 1 ◽  
Glycosylphosphatidyl Inositol

ABSTRACT The relationship between glycosylphosphatidyl inositol (GPI)-linked proteins and caveolins remains controversial. Here, we derived fibroblasts from Cav-1 null mouse embryos to study the behavior of GPI-linked proteins in the absence of caveolins. These cells lack morphological caveolae, do not express caveolin-1, and show a ∼95% down-regulation in caveolin-2 expression; these cells also do not express caveolin-3, a muscle-specific caveolin family member. As such, these caveolin-deficient cells represent an ideal tool to study the role of caveolins in GPI-linked protein sorting. We show that in Cav-1 null cells GPI-linked proteins are preferentially retained in an intracellular compartment that we identify as the Golgi complex. This intracellular pool of GPI-linked proteins is not degraded and remains associated with intracellular lipid rafts as judged by its Triton insolubility. In contrast, GPI-linked proteins are transported to the plasma membrane in wild-type cells, as expected. Furthermore, recombinant expression of caveolin-1 or caveolin-3, but not caveolin-2, in Cav-1 null cells complements this phenotype and restores the cell surface expression of GPI-linked proteins. This is perhaps surprising, as GPI-linked proteins are confined to the exoplasmic leaflet of the membrane, while caveolins are cytoplasmically oriented membrane proteins. As caveolin-1 normally undergoes palmitoylation on three cysteine residues (133, 143, and 156), we speculated that palmitoylation might mechanistically couple caveolin-1 to GPI-linked proteins. In support of this hypothesis, we show that palmitoylation of caveolin-1 on residues 143 and 156, but not residue 133, is required to restore cell surface expression of GPI-linked proteins in this complementation assay. We also show that another lipid raft-associated protein, c-Src, is retained intracellularly in Cav-1 null cells. Thus, Golgi-associated caveolins and caveola-like vesicles could represent part of the transport machinery that is necessary for efficiently moving lipid rafts and their associated proteins from the trans-Golgi to the plasma membrane. In further support of these findings, GPI-linked proteins were also retained intracellularly in tissue samples derived from Cav-1 null mice (i.e., lung endothelial and renal epithelial cells) and Cav-3 null mice (skeletal muscle fibers).

scholarly journals Contribution of Ezrin on the Cell Surface Plasma Membrane Localization of Programmed Cell Death Ligand-1 in Human Choriocarcinoma JEG-3 Cells

2021 ◽  
Vol 14 (10) ◽  
pp. 963
Author(s):  
Mayuka Tameishi ◽  
Takuro Kobori ◽  
Chihiro Tanaka ◽  
Yoko Urashima ◽  
Takuya Ito ◽  
...  
Keyword(s):  
Cell Death ◽  
Plasma Membrane ◽  
Programmed Cell Death ◽  
Cell Surface ◽  
Mrna Level ◽  
Single Agent ◽  
Surface Expression ◽  
Immune Checkpoint Blockade ◽  
Cell Surface Expression ◽  
New Strategy

Immune checkpoint blockade (ICB) antibodies targeting programmed cell death ligand-1 (PD-L1) and programmed cell death-1 (PD-1) have improved survival in patients with conventional single agent chemotherapy-resistant gestational trophoblastic neoplasia (GTN). However, many patients are resistant to ICB therapy, the mechanisms of which are poorly understood. Unraveling the regulatory mechanism for PD-L1 expression may provide a new strategy to improve ICB therapy in patients with GTN. Here, we investigated whether the ezrin/radixin/moesin (ERM) family, i.e., a group of scaffold proteins that crosslink actin cytoskeletons with several plasma membrane proteins, plays a role in the regulation of PD-L1 expression using JEG-3 cells, a representative human choriocarcinoma cell line. Our results demonstrate mRNA and protein expressions of ezrin, radixin, and PD-L1, as well as their colocalization in the plasma membrane. Intriguingly, immunoprecipitation experiments revealed that PD-L1 interacted with both ezrin and radixin and the actin cytoskeleton. Moreover, gene silencing of ezrin but not radixin strongly diminished the cell surface expression of PD-L1 without altering the mRNA level. These results indicate that ezrin may contribute to the cell surface localization of PD-L1 as a scaffold protein in JEG-3 cells, highlighting a potential therapeutic target to improve the current ICB therapy in GTN.

scholarly journals Proteomic Plasma Membrane Profiling Reveals an Essential Role for gp96 in the Cell Surface Expression of LDLR Family Members, Including the LDL Receptor and LRP6

2012 ◽  
Vol 11 (3) ◽  
pp. 1475-1484 ◽  
Author(s):  
Michael P. Weekes ◽  
Robin Antrobus ◽  
Suzanne Talbot ◽  
Simon Hör ◽  
Nikol Simecek ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Essential Role ◽  
Family Members ◽  
Ldl Receptor ◽  
Surface Expression ◽  
Cell Surface Expression

scholarly journals Glycosylation Is Important for Cell Surface Expression of the Water Channel Aquaporin-2 but Is Not Essential for Tetramerization in the Endoplasmic Reticulum

2003 ◽  
Vol 279 (4) ◽  
pp. 2975-2983 ◽  
Author(s):  
Giel Hendriks ◽  
Marco Koudijs ◽  
Bas W. M. van Balkom ◽  
Viola Oorschot ◽  
Judith Klumperman ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Surface ◽  
Water Channel ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Aquaporin 2

The PDZ-interaction of the intestinal anion exchanger downregulated in adenoma (DRA; SLC26A3) facilitates its movement into Rab11a-positive recycling endosomes

2013 ◽  
Vol 304 (11) ◽  
pp. G980-G990 ◽  
Author(s):  
S. Lissner ◽  
C.-J. Hsieh ◽  
L. Nold ◽  
K. Bannert ◽  
P. Bodammer ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Surface Expression ◽  
Dominant Negative ◽  
Cell Surface Expression ◽  
Dominant Negative Mutant ◽  
Recycling Endosomes ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Recycling Pathway

Electroneutral NaCl absorption in the ileum and colon is mediated by downregulated in adenoma (DRA) (Cl-/HCO3- exchanger; SLC26A3) and Na+/H+ exchanger 3 (NHE3, SLC9A3). Surface expression of transport proteins undergoes basal and regulated recycling by endo- and exocytosis. Expression and activity of DRA in the plasma membrane depend on intact lipid rafts, phosphatidylinositol 3-kinase (PI3-kinase), and the PDZ interaction of DRA. However, it is unknown how the PDZ interaction of DRA affects its trafficking to the cell surface. Therefore, the (re)cycling pathway of DRA was investigated in HEK cells stably expressing enhanced green fluorescent protein (EGFP)-DRA or EGFP-DRA-ETKFminus (a mutant lacking the PDZ interaction motif). Early, late, and recycling endosomes were immunoisolated by precipitating stably transfected mCherry-hemagglutinin (HA)-Rab5a, -7a, or -11a. EGFP-DRA and EGFP-DRA-ETKFminus were equally present in early endosomes. In recycling endosomes, wild-type DRA was preferentially present, whereas, in late endosomes, DRA-ETKF-minus dominated. Correspondingly, EGFP-DRA colocalized with mCherry-HA-Rab11a in recycling endosomes, whereas EGFP-DRA-ETKFminus colocalized with mCherry-HA-Rab7a in late endosomes. Functionally, this different distribution was reflected by a shorter half-life of the mutant DRA. Transient expression of dominant-negative Rab11aS25N inhibited the activity (-17%, P < 0.05) and the cell surface expression of DRA (-30%, P < 0.05). Transient transfection of Rab4a or its dominant-negative mutant Rab4aS22N was without effect and thus excluded participation of the rapid recycling pathway. Taken together, the PDZ interaction of DRA facilitates its movement into Rab11a-positive recycling endosomes, from where it is inserted in the plasma membrane. A scenario emerges where specific PDZ adaptor proteins are present along several compartments of the endocytosis-recycling pathway.

scholarly journals Secretory carrier-associated membrane protein 2 (SCAMP2) regulates cell surface expression of T-type calcium channels

2022 ◽  
Vol 15 (1) ◽  
Author(s):  
Leos Cmarko ◽  
Robin N. Stringer ◽  
Bohumila Jurkovicova-Tarabova ◽  
Tomas Vacik ◽  
Lubica Lacinova ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Mammalian Cells ◽  
Neuronal Excitability ◽  
Low Voltage ◽  
Activity Patterns ◽  
Surface Expression ◽  
Single Amino Acid ◽  
Cell Surface Expression ◽  
Charge Movement

AbstractLow-voltage-activated T-type Ca2+ channels are key regulators of neuronal excitability both in the central and peripheral nervous systems. Therefore, their recruitment at the plasma membrane is critical in determining firing activity patterns of nerve cells. In this study, we report the importance of secretory carrier-associated membrane proteins (SCAMPs) in the trafficking regulation of T-type channels. We identified SCAMP2 as a novel Cav3.2-interacting protein. In addition, we show that co-expression of SCAMP2 in mammalian cells expressing recombinant Cav3.2 channels caused an almost complete drop of the whole cell T-type current, an effect partly reversed by single amino acid mutations within the conserved cytoplasmic E peptide of SCAMP2. SCAMP2-induced downregulation of T-type currents was also observed in cells expressing Cav3.1 and Cav3.3 channel isoforms. Finally, we show that SCAMP2-mediated knockdown of the T-type conductance is caused by the lack of Cav3.2 expression at the cell surface as evidenced by the concomitant loss of intramembrane charge movement without decrease of total Cav3.2 protein level. Taken together, our results indicate that SCAMP2 plays an important role in the trafficking of Cav3.2 channels at the plasma membrane.

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