Hydrophobic ion transfer between membranes of adjacent hepatocytes: a possible probe of tight junction structure.
The topology of the tight junction is probed by introducing dipicrylamine (dpa-), a lipid-soluble anion, into the membranes of hepatocyte pairs in culture. Once partitioned into the membrane, dpa- ions are free to move in the hydrophobic core of the membrane, where their mobile charges greatly increase membrane capacitance. If tight junctions are lines of membrane fusion, dpa- will cross the tight junction without traversing a polar headgroup layer. Furthermore, the electric potential across the tight junction will be equal to the difference in membrane potentials of the two cells. dpa- can therefore be expected to move electrophoretically from cell membrane to cell membrane across the junction in response to an intercellular voltage difference. Experiments performed under double whole-cell clamp show that this transfer occurs as follows: First, dpa- causes an intercellular current unrelated to gap junctions to flow in response to an intercellular voltage difference. Second, this electrophoretic removal or addition of dpa- from a cell's membrane through the tight junction must reduce or increase its dpa- content and thus its capacitance. Experiments confirm this prediction: We detect rapid, symmetric, and reversible changes in membrane capacitance in response to changes in the membrane potential of the neighboring cell. Finally, we find that hepatocyte membranes contain a negatively charged endogenous molecule that contain a negatively charged endogenous molecule that can move from cell to cell like dpa- under the influence of an intercellular potential difference. We conclude that membrane fusion occurs at tight junctions and that this hydrophobic intercellular pathway can play a role in intercellular communication.
Turin
L
L
Unité Associée 671, Centre National de la Recherche Scientifique, Villefranche, France.
Béhé
P
P
Plonsky
I
I
Dunina-Barkovskaya
A
A
D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D004553:Electric Conductivity / Q000187:drug effects; D004594:Electrophysiology / Q000379:methods; D007365:Intercellular Junctions / Q000187:drug effects / Q000502:physiology*; D008099:Liver / Q000502:physiology*; D051379:Mice; D008954:Models, Biological; D010851:Picrates / Q000494:pharmacology*; D014634:Valinomycin / Q000494:pharmacology
D010851:Picrates; C011454:dipicrylamine; D014634:Valinomycin