Summary
Cells of organs and tissues commonly communicate directly with one another via permeable membrane junctions. Cell-to-cell channels, spanning the width of both membranes of a junction, are thought to provide the pathways between the cytoplasms of adjacent cells for the immediate exchange of ions and small molecules. We study these cell-to-cell channels in a cell model system, the salivary gland ofChironomus. Using intracellularly injected fluorescent labelled peptides and oligosaccharides of various molecular dimensions as channel permeability probes we find the channels to have a bore of about 2 nm. The channel permeability can be modulated and, in the extreme, the channels can be closed under various experimental conditions. With the aid of the Ca2+-sensitive photoprotein aequorin as monitor of cytoplasmic free Ca2+ concentration, we show that a determining factor in this modulation of channel permeability is the cytoplasmic free Ca2+ concentration. Moreover, results obtained by injection of different-sized and different-labelled channel permeability probes together with Ca2+ indicate that closure of the individual channels may occur in more than one step, i.e., by a graded reduction of channel bore.
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This symposium was supported, in part by Contract 263-MD-025754 from the National Cancer Institute and the Fogarty International Center. This work was supported by NH Grants 5P1GM23911-07 and 5T32-6M07403-04.
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Rose, B. Permeability of the cell-to-cell membrane channel and its regulation in an insect cell junction. In Vitro 16, 1029–1042 (1980). https://doi.org/10.1007/BF02619253
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DOI: https://doi.org/10.1007/BF02619253