Connexin-Based Channels in Astrocytes: How to Study Their Properties

Giaume, Christian; Orellana, Juan A.; Abudara, Verónica; Sáez, Juan C.

doi:10.1007/978-1-61779-452-0_19

Cited by 31 publications

(36 citation statements)

References 51 publications

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“…c These proposed Cx38-mediated currents were not visible in other oocyte batches exposed to a similar experimental protocol (n = 4, unpublished results) whether complete opening of Cx43 hemichannels requires an undefined cellular or experimental factor. Factors of interest that may differ between laboratory protocols and cellular systems could be (1) presence or absence of certain interaction partners, (2) presence of a free C-terminal fragment of Cx43 in some cell lines [126], (3) different composition of experimental solutions and/or usage of ultra-pure water in experimental solutions [127,128], (4) composition of cell culture medium [15,106], (5) non-physiological experimental pH (5.8/8.0) and temperatures (i.e., 4 °C) [43,92], and (6) associated mechanical strain upon solution change [49]. The baseline uptake of fluorescent dyes is significant in many cell types which calls for strict experimental design including parallel experiments of equal number of treated versus non-treated cells (or WT versus KO) obtained from a number of separate astrocyte/cell preparations.…”

Section: Future Challenges and Directionsmentioning

confidence: 99%

Connexin Hemichannels in Astrocytes: An Assessment of Controversies Regarding Their Functional Characteristics

et al. 2017

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Astrocytes in the mammalian central nervous system are interconnected by gap junctions made from connexins of the subtypes Cx30 and Cx43. These proteins may exist as hemichannels in the plasma membrane in the absence of a 'docked' counterpart on the neighboring cell. A variety of stimuli are reported to open the hemichannels and thereby create a permeation pathway through the plasma membrane. Cx30 and Cx43 have, in their hemichannel configuration, been proposed to act as ion channels and membrane pathways for different molecules, such as fluorescent dyes, ATP, prostaglandins, and glutamate. Published studies about astrocyte hemichannel behavior, however, have been highly variable and/or contradictory. The field of connexin hemichannel research has been complicated by great variability in the experimental preparations employed, a lack of highly specific pharmacological inhibitors and by confounding changes associated with genetically modified animal models. This review attempts to critically assess the gating, inhibition and permeability of astrocytic connexin hemichannels and proposes that connexins in their hemichannel configuration act as gated pores with isoform-specific permeant selectivity. We expect that some, or all, of the controversies discussed here will be resolved by future research and sincerely hope that this review serves to motivate such clarifying investigations.

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Section: Future Challenges and Directionsmentioning

confidence: 99%

Connexin Hemichannels in Astrocytes: An Assessment of Controversies Regarding Their Functional Characteristics

et al. 2017

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“…125 Briefly, the cell monolayer on glass coverslips were washed twice with Locke's solution containing 154 mM NaCl, 5.4 mM KCl, 2.3 mM CaCl 2 and 5 mM HEPES at pH7.5, and incubated in 5 μM ethidium bromide. Hemichannel were opened by application of Ca 2+/ Mg 2+ free medium.…”

Section: Hemichannel Assaymentioning

confidence: 99%

Astrocytes promote glioma invasion via the gap junction protein connexin43

et al. 2015

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Reactive astrocytes are integral to the glioma microenvironment. Connexin43 (Cx43) is a major gap junction protein in astrocytes and its expression is enhanced significantly in glioma-associated astrocytes, especially at the peri-tumoral region. Although downregulation of Cx43-mediated intercellular communication is associated with increased malignancy in tumor cells, the role of Cx43 in stromal cells in glioma progression is not defined. Using a mouse model consisting of syngeneic intracranial implantation of GL261 glioma cells into Nestin-Cre:Cx43(fl/fl) mice where Cx43 was eliminated in astrocytes, we demonstrate a role of astrocytic Cx43 in the dissemination of glioma cells from the tumor core. To determine whether heterocellular communication between astrocytes and glioma cells is essential for reduced invasion in the absence of astrocytic Cx43, we abolished channel formation between glioma cells and astrocytes by either knocking down Cx43 in glioma cells with short hairpin RNA (shRNA) or overexpressing a dominant-negative channel-defective Cx43-T154A mutant in these cells. Although Cx43shRNA in glioma cells reduced invasion, expression of Cx43-T154A had no effect on glioma invasion, suggesting tumoral Cx43 may influence motility independently from its channel function. Alteration in astrocytic Cx43 function, such as by replacing the wild-type allele with a C-terminal truncated Cx43 mutant exhibiting reduced intercellular coupling, is sufficient to reduce glioma spreading into the brain parenchyma. Our results reveal a novel role of astrocytic Cx43 in the formation of an invasive niche and raise the possibility to control glioma progression by manipulating the microenvironment.

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“…Biochemical intercellular transfer (such as glucose or ATP) has been extensively studied using passive dyes loaded in the astrocytic network through a patch pipette (Giaume et al, 2012). Complementary information has also been obtained in culture using paired recording of connected astrocytes, allowing assessment of gap junctional conductances; in weakly coupled pairs, even single gap junctional channel events could be detected (Giaume et al, 1991).…”

Section: Astrocytic Properties Determined By Electrophysiological Recmentioning

confidence: 99%

How do astrocytes shape synaptic transmission? Insights from electrophysiology

Dallérac¹,

Chever²,

Rouach³

2013

Front. Cell. Neurosci.

144

117

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A major breakthrough in neuroscience has been the realization in the last decades that the dogmatic view of astroglial cells as being merely fostering and buffering elements of the nervous system is simplistic. A wealth of investigations now shows that astrocytes actually participate in the control of synaptic transmission in an active manner. This was first hinted by the intimate contacts glial processes make with neurons, particularly at the synaptic level, and evidenced using electrophysiological and calcium imaging techniques. Calcium imaging has provided critical evidence demonstrating that astrocytic regulation of synaptic efficacy is not a passive phenomenon. However, given that cellular activation is not only represented by calcium signaling, it is also crucial to assess concomitant mechanisms. We and others have used electrophysiological techniques to simultaneously record neuronal and astrocytic activity, thus enabling the study of multiple ionic currents and in depth investigation of neuro-glial dialogues. In the current review, we focus on the input such approach has provided in the understanding of astrocyte-neuron interactions underlying control of synaptic efficacy.

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Connexin-Based Channels in Astrocytes: How to Study Their Properties

Cited by 31 publications

References 51 publications

Connexin Hemichannels in Astrocytes: An Assessment of Controversies Regarding Their Functional Characteristics

Connexin Hemichannels in Astrocytes: An Assessment of Controversies Regarding Their Functional Characteristics

Astrocytes promote glioma invasion via the gap junction protein connexin43

How do astrocytes shape synaptic transmission? Insights from electrophysiology

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