Diameter of the Cell-to-Cell Junctional Membrane Channels as Probed with Neutral Molecules

Abstract

The cell-to-cell channels in the junctions of an insect salivary gland and of insect and mammalian cells in culture were probed with fluorescent molecules-neutral linear oligosaccharides, neutral branched glycopeptides, and charged linear peptides. From the molecular dimensions of the largest permeants and smallest impermeants the permeation-limiting channel diameter was obtained: 16 to 20 angstroms for the mammalian cells and 20 to 30 angstroms for the insect cells.

Oligomeric Structure and Functional Characterization of Caenorhabditis elegans Innexin-6 Gap Junction Protein

“…Our results indicate that INX-6 forms similar but distinct gap junction channels from connexins in terms of the molecular dimensions and permeability. These findings are consistent with the notion that invertebrates possess a wide limiting pore diameter as compared with vertebrates (26).…”

“…Another study using fluorescent molecules conjugated with oligosaccharides, neutral branched glycopeptides, and charged linear peptides showed the transfer of molecules up to ϳ3 kDa (26). It is therefore not surprising that the 3k-TR tracer passed through the INX-6 channels in this study.…”

Primary Cultures of Chick Osteocytes Retain Functional Gap Junctions between Osteocytes and between Osteocytes and Osteoblasts

“…When the connexons in the plasma membranes of two adjacent cells are aligned, they form a continuous aqueous channel through which small molecules~, 1 kD! may pass~Flagg- Newton et al, 1979;Schwarzmann et al, 1981!. Cx43 is the predominant gap junction protein expressed by bone cells~Jones et al, 1993;Ilvesaro et al, 2000!. Gap junction channels allow intercellular transmission of signaling ions and second messenger molecules and have been thought to play several functions in bone, including the transmission of mechanical and chemical signals from one area of bone to another and the ability of the cellular network to initiate a coordinated response to external stimuli~Schiller et al, 1992;Xia & Ferrier, 1992;Donahue et al, 1995;Vander Molen et al, 1996;Jorgensen et al, 1997!.…”

Transcription of the gene for the gap junctional protein connexin43 and expression of functional cell-to-cell channels are regulated by cAMP.

“…The cells in most tissues are interconnected by channels in their membrane junctions (gap junctions) that provide a direct intercellular pathway for molecules up to 1500-2000 kDa (Flagg-Newton et al, 1979;Schwartzmann et al, 1981). Evidence is mounting that these cell-cell channels transmit growth controlling signals and thus are instrumental in the maintenance of growth control in normal cells (see Loewenstein and Rose, 1992).…”