Immunological approaches to gap junctions: Studies of immuno-localization, membrane protein topology, and function

1989 ◽  
Vol 47 ◽  
pp. 812-813
Author(s):  
Ross G. Johnson ◽  
Tze-Hong Lu ◽  
Kathleen Klukas ◽  
Larry Takemoto ◽  
S. Barbara Yancey
Keyword(s):  
Gap Junctions ◽  
Plasma Membranes ◽  
Strong Support ◽  
Membrane Domains ◽  
Biological Processes ◽  
Animal Cells ◽  
Membrane Protein Topology ◽  
A Cell ◽  
Clear Identification ◽  
And Function

It is now widely accepted that the plasma membranes of epithelial cells display a marked degree of polarity. This polarity is reflected in a number of parameters, e.g. the localization of certain proteins to basolateral membranes. Polarity is also illustrated by the presence of discrete membrane specializations, including desmosomes, tight junctions and gap junctions. These specializations provide strong support for the idea of membrane "domains" within the polarized membrane of the epithelial cell. This presentation relates to the proteins found in gap junction membranes. The issues include a clear identification of these proteins in different cells and an analysis of how a cell-to-cell channel is constructed by these proteins.The plasma membranes of most animal cells contain cell-to-cell channels, which provide for the direct, passive exchange of small molecules between cells. Collections of these channels are identified as "gap junctions." This form of intercellular communication is thought to be important in a wide variety of biological processes, including cellular differentiation, proliferation, and tissue homeostasis.

scholarly journals Membrane Domain Specificity in the Spatial Distribution of Aquaporins 5, 7, 9, and 11 in Efferent Ducts and Epididymis of Rats

2008 ◽  
Vol 56 (12) ◽  
pp. 1121-1135 ◽  
Author(s):  
Louis Hermo ◽  
Morgan Schellenberg ◽  
Lauren Ye Liu ◽  
Bama Dayanandan ◽  
Tong Zhang ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Plasma Membranes ◽  
Water Channel ◽  
Wide Field ◽  
Membrane Domains ◽  
Efferent Ducts ◽  
Specific Manner ◽  
Basal Plasma ◽  
A Cell ◽  
Specific Membrane

Water content within the epididymis of the male reproductive system is stringently regulated to promote sperm maturation. Several members of the aquaporin (AQP) family of water channel-forming integral membrane proteins have been identified in epididymal cells, but expression profiling for this epithelium is presently incomplete, and no AQP isoform has yet been identified on basolateral plasma membranes of these cells. In this study, we explored AQP expression by RT-PCR and light microscopy immunolocalizations using peroxidase and wide-field fluorescence techniques. The results indicate that several AQPs are coexpressed in the epididymis including AQP 5, 7, 9, and 11. Immunolocalizations suggested complex patterns in the spatial distribution of these AQPs. In principal cells, AQP 9 and 11 were present mainly on microvilli, whereas AQP 7 was localized primarily to lateral and then to basal plasma membranes in a region-specific manner. AQP 5 was also expressed regionally but was associated with membranes of endosomes. Additionally, AQPs were expressed by some but not all basal (AQP 7 and 11), clear (AQP 7 and 9), and halo (AQP 7 and 11) cells. These findings indicate unique associations of AQPs with specific membrane domains in a cell type- and region-specific manner within the epididymis of adult animals.

scholarly journals Cl--stimulated adenosine triphosphatase: existence, location and function

1983 ◽  
Vol 106 (1) ◽  
pp. 143-161
Author(s):  
G. A. Gerencser ◽  
S. H. Lee
Keyword(s):  
Atpase Activity ◽  
Plasma Membranes ◽  
Direct Evidence ◽  
Chloride Transport ◽  
Indirect Evidence ◽  
Transport Processes ◽  
Animal Cells ◽  
Chemical Mechanisms ◽  
Mitochondrial Origin ◽  
And Function

The three universally accepted mechanisms of chloride transport across plasma membranes are: (i) sodium-coupled symport; (ii) anion-coupled antiport; and (iii) coupling to primary ion transport through electrical and/or chemical mechanisms. No direct evidence has been provided for primary chloride transport despite numerous reports of cellular, anion-stimulated ATPases and of chloride transport processes. Anion-stimulated ATPases are of mitochondrial origin and are a ubiquitous property of practically all animal cells. It also appears that there are other subcellular sites of anion-stimulated ATPase activity, especially the plasma membranes. Recent studies have provided indirect evidence (through parallel studies on the same tissue of anion-stimulated ATPase activity and chloride fluxes) which suggests a possible involvement of ATPase in net movement of chloride up its electrochemical gradient across plasma membranes. Further studies are required to substantiate a direct transport function to Cl--stimulated ATPases located in the plasma membrane.

Direct demonstration of the endocytic function of caveolae by a cell-free assay

1999 ◽  
Vol 112 (7) ◽  
pp. 1101-1110 ◽  
Author(s):  
A. Gilbert ◽  
J.P. Paccaud ◽  
M. Foti ◽  
G. Porcheron ◽  
J. Balz ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Incubation Medium ◽  
Plasma Membranes ◽  
Cultured Cells ◽  
Significant Proportion ◽  
Membrane Domains ◽  
Direct Demonstration ◽  
Fractionation Analysis ◽  
A Cell ◽  
Endocytic Vesicles

The endocytic function of caveolae was challenged by taking advantage of a cell-free assay directly measuring the detachment of receptor-containing vesicles from isolated plasma membranes. Plasma membranes from cultured cells surface-labeled with 125I-cholera toxin (segregating in caveolae) were isolated as described previously. Following incubation of these labeled membranes in the presence of nucleotide(s) and cytosol, a significant proportion of the initially membrane-associated radioactivity was released into the incubation medium in sedimentable form (14*10(6)g). Results of biochemical, morphological, and fractionation analysis of the material containing the released radioactivity directly demonstrated that caveolae are plasma membrane domains involved in an endocytic process and resulting in the formation of caveolae-derived vesicles. In addition, these studies allowed a direct comparison of caveolae- and clathrin-coated pit-mediated endocytosis and reveal that these two processes diverge in terms of kinetics, cytosol and nucleotide requirements as well as in terms of the density and size of the endocytic vesicles formed.

scholarly journals A Cell-free System to Study Regulation of Focal Adhesions and of the Connected Actin Cytoskeleton

1999 ◽  
Vol 10 (2) ◽  
pp. 373-391 ◽  
Author(s):  
Anna Cattelino ◽  
Chiara Albertinazzi ◽  
Mario Bossi ◽  
David R. Critchley ◽  
Ivan de Curtis
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Polymerization ◽  
Plasma Membranes ◽  
Molecular Mechanisms ◽  
Divalent Cations ◽  
Focal Adhesions ◽  
Free System ◽  
Β1 Integrins ◽  
A Cell ◽  
And Function

Assembly and modulation of focal adhesions during dynamic adhesive processes are poorly understood. We describe here the use of ventral plasma membranes from adherent fibroblasts to explore mechanisms regulating integrin distribution and function in a system that preserves the integration of these receptors into the plasma membrane. We find that partial disruption of the cellular organization responsible for the maintenance of organized adhesive sites allows modulation of integrin distribution by divalent cations. High Ca2+ concentrations induce quasi-reversible diffusion of β1 integrins out of focal adhesions, whereas low Ca2+ concentrations induce irreversible recruitment of β1 receptors along extracellular matrix fibrils, as shown by immunofluorescence and electron microscopy. Both effects are independent from the presence of actin stress fibers in this system. Experiments with cells expressing truncated β1 receptors show that the cytoplasmic portion of β1 is required for low Ca2+-induced recruitment of the receptors to matrix fibrils. Analysis with function-modulating antibodies indicates that divalent cation-mediated receptor distribution within the membrane correlates with changes in the functional state of the receptors. Moreover, reconstitution experiments show that purified α-actinin colocalizes and redistributes with β1 receptors on ventral plasma membranes depleted of actin, implicating binding of α-actinin to the receptors. Finally, we found that recruitment of exogenous actin is specifically restricted to focal adhesions under conditions in which new actin polymerization is inhibited. Our data show that the described system can be exploited to investigate the mechanisms of integrin function in an experimental setup that permits receptor redistribution. The possibility to uncouple, under cell-free conditions, events involved in focal adhesion and actin cytoskeleton assembly should facilitate the comprehension of the underlying molecular mechanisms.

Gap junctions between dendrites and somata of neurons in the primate sensori-motor cortex

1978 ◽  
Vol 203 (1150) ◽  
pp. 39-47 ◽  
Keyword(s):  
Motor Cortex ◽  
Gap Junctions ◽  
Plasma Membranes ◽  
Stellate Cells ◽  
Electrical Transmission ◽  
Cell Soma ◽  
Deep Layers ◽  
Sensory Cortices ◽  
A Cell ◽  
Presynaptic Dendrites

Gap junctions have been found infrequently between two dendrites or a dendrite and a cell soma in the deep layers of both the motor and somatic sensory cortices of the primate. At these junctions the outer leaflets of the plasma membranes of both profiles are intimately apposed with a gap of 2 nm between them which shows a structure of hexagonal subunits in tangential sections. These gap junctions occur mainly between the dendrites or dendrites and somata of large stellate cells but are also associated in some examples with a dendro-dendritic synapse and thus occur between large stellate dendrites and presynaptic dendrites; a desmosome may also occur in association with a gap junction and dendro-dendritic synapse. Gap junctions have been identified as sites of electrical transmission between cells in a number of sites and it is therefore suggested that some neurons in the sensori-motor cortex are electrotonically coupled.

scholarly journals COP-coated vesicles are involved in the mitotic fragmentation of Golgi stacks in a cell-free system.

1994 ◽  
Vol 125 (2) ◽  
pp. 269-282 ◽  
Author(s):  
T Misteli ◽  
G Warren
Keyword(s):  
Strong Support ◽  
Serial Sectioning ◽  
Animal Cells ◽  
Cdc2 Kinase ◽  
Cross Sectional ◽  
Free System ◽  
Transport Vesicles ◽  
A Cell ◽  
Gamma S ◽  
Total Membrane

Rat liver Golgi stacks fragmented when incubated with mitotic but not interphase cytosol in a process dependent on time, temperature, energy (added in the form of ATP) and cdc2 kinase. The cross-sectional length of Golgi stacks fell in the presence of mitotic cytosol by approximately 50% over 30 min without a corresponding decrease in the number of cisternae in the stack. The loss of membrane from stacked and single cisternae occurred with a half-time of approximately 20 min, and was matched by the appearance of both small (50-100 nm in diameter) and large (100-200 nm in diameter) vesicular profiles. Small vesicular profiles constituted more than 50% of the total membrane after 60 min of incubation and they were shown to be vesicles or very short tubules by serial sectioning. In the presence of GTP gamma S all of the small vesicles were COP-coated and both the extent and the rate at which they formed were sufficient to account for the production of small vesicles during mitotic incubation. The involvement of the COP-mediated budding mechanism was confirmed by immunodepletion of one of the subunits of COP coats (the coatomer) from mitotic cytosol. Vesicles were no longer formed but highly fenestrated networks appeared, an effect reversed by the readdition of purified coatomer. Together these experiments provide strong support for our hypothesis that the observed vesiculation of the Golgi apparatus during mitosis in animal cells is caused by continued budding of COP-coated transport vesicles but an inhibition of their fusion with their target membranes.

scholarly journals FOXK2 Transcription Factor and Its Emerging Roles in Cancer

Cancers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 393 ◽  
Author(s):  
Gabriela Nestal de Moraes ◽  
Luciana Carneiro ◽  
Raquel Maia ◽  
Eric Lam ◽  
Andrew Sharrocks
Keyword(s):  
Prognostic Value ◽  
Large Family ◽  
Biological Processes ◽  
Biological Functions ◽  
Invasion And Metastasis ◽  
Complex Interactions ◽  
Forkhead Box ◽  
A Cell ◽  
And Function

Forkhead box (FOX) transcription factors compose a large family of regulators of key biological processes within a cell. FOXK2 is a member of FOX family, whose biological functions remain relatively unexplored, despite its description in the early nineties. More recently, growing evidence has been pointing towards a role of FOXK2 in cancer, which is likely to be context-dependent and tumour-specific. Here, we provide an overview of important aspects concerning the mechanisms of regulation of FOXK2 expression and function, as well as its complex interactions at the chromatin level, which orchestrate how it differentially regulates the expression of gene targets in pathophysiology. Particularly, we explore the emerging functions of FOXK2 as a regulator of a broad range of cancer features, such as cell proliferation and survival, DNA damage, metabolism, migration, invasion and metastasis. Finally, we discuss the prognostic value of assessing FOXK2 expression in cancer patients and how it can be potentially targeted for future anticancer interventions.

Structural modifications of intercellular junctions.

1978 ◽  
Vol 36 (2) ◽  
pp. 330-331
Author(s):  
J. Metz ◽  
M. Merlo ◽  
W. G. Forssmann
Keyword(s):  
Gap Junctions ◽  
Intercellular Junctions ◽  
Cell Isolation ◽  
Extrahepatic Cholestasis ◽  
Structural Modifications ◽  
Pancreatic Duct Ligation ◽  
Pancreatic Cells ◽  
Duct Ligation ◽  
Thin Sectioning ◽  
And Function

Structure and function of intercellular junctions were studied under the electronmicroscope using conventional thin sectioning and freeze-etch replicas. Alterations of tight and gap junctions were analyzed 1. of exocrine pancreatic cells under cell isolation conditions and pancreatic duct ligation and 2. of hepatocytes during extrahepatic cholestasis.During the different steps of cell isolation of exocrine pancreatic cells, gradual changes of tight and gap junctions were observed. Tight junctions, which formed belt-like structures around the apex of control acinar cells in situ, subsequently diminished, became interrupted and were concentrated into macular areas (Fig. 1). Aggregations of membrane associated particles, which looked similar to gap junctions, were intermixed within tight junctional areas (Fig. 1). These structures continously disappeared in the last stages of the isolation procedure. The intercellular junctions were finally separated without destroying the integrity of the cell membrane, which was confirmed with porcion yellow, lanthanum chloride and horse radish peroxidase.

Membrane microdomains: lessons from microscopy

1995 ◽  
Vol 53 ◽  
pp. 776-777
Author(s):  
J.M. Robinson ◽  
J.M Oliver
Keyword(s):  
Spatial Distribution ◽  
Plasma Membrane ◽  
Epithelial Cells ◽  
Plasma Membranes ◽  
Cell Types ◽  
Imaging Modalities ◽  
Membrane Microdomains ◽  
Membrane Domains ◽  
Lateral Heterogeneity ◽  
Functional Importance

Specialized regions of plasma membranes displaying lateral heterogeneity are the focus of this Symposium. Specialized membrane domains are known for certain cell types such as differentiated epithelial cells where lateral heterogeneity in lipids and proteins exists between the apical and basolateral portions of the plasma membrane. Lateral heterogeneity and the presence of microdomains in membranes that are uniform in appearance have been more difficult to establish. Nonetheless a number of studies have provided evidence for membrane microdomains and indicated a functional importance for these structures.This symposium will focus on the use of various imaging modalities and related approaches to define membrane microdomains in a number of cell types. The importance of existing as well as emerging imaging technologies for use in the elucidation of membrane microdomains will be highlighted. The organization of membrane microdomains in terms of dimensions and spatial distribution is of considerable interest and will be addressed in this Symposium.

CD38 as an immunomodulator in cancer

2020 ◽  
Vol 16 (34) ◽  
pp. 2853-2861
Author(s):  
Yanli Li ◽  
Rui Yang ◽  
Limo Chen ◽  
Sufang Wu
Keyword(s):  
Multiple Myeloma ◽  
Cell Activation ◽  
Human Tissues ◽  
Transmembrane Glycoprotein ◽  
Cell Activation Marker ◽  
Research Findings ◽  
A Cell ◽  
And Function ◽  
Human Molecule

CD38 is a transmembrane glycoprotein that is widely expressed in a variety of human tissues and cells, especially those in the immune system. CD38 protein was previously considered as a cell activation marker, and today monoclonal antibodies targeting CD38 have witnessed great achievements in multiple myeloma and promoted researchers to conduct research on other tumors. In this review, we provide a wide-ranging review of the biology and function of the human molecule outside the field of myeloma. We focus mainly on current research findings to summarize and update the findings gathered from diverse areas of study. Based on these findings, we attempt to extend the role of CD38 in the context of therapy of solid tumors and expand the role of the molecule from a simple marker to an immunomodulator.

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