Properties and Regulation of Gap Junctional Hemichannels in the Plasma Membranes of Cultured Cells

During the assembly of gap junctions, a hemichannel in the plasma membrane of one cell is thought to align and dock with another in an apposed membrane to form a cell-to-cell channel. We report here on the existence and properties of nonjunctional, plasma membrane connexin43 (Cx43) hemichannels. The...

Full description

Saved in:
Bibliographic Details
Published in:The Journal of cell biology 1996-08, Vol.134 (4), p.1019-1030
Main Authors: Li, Haiying, Liu, Tai-Feng, Lazrak, Ahmed, Peracchia, Camillo, Goldberg, Gary S., Lampe, Paul D., Johnson, Ross G.
Format: Article
Language:English
Subjects:
Alcohols - pharmacology
Animals
Biological Transport - drug effects
Calcium
Calcium - pharmacology
Carcinoma, Hepatocellular
Cell lines
Cell Membrane - physiology
Cell membranes
Cells
Cells, Cultured
Cellular biology
Connexin 43 - physiology
Connexins
DNA, Antisense
Dyes
Enzyme Activation - drug effects
Fluoresceins
Fluorescent Dyes
Gap junctions
Gap Junctions - physiology
HeLa Cells
Humans
Kidney
Magnesium - pharmacology
Membranes
Octanols
Oncogene Protein pp60(v-src) - physiology
P branes
Protein Kinase C - physiology
Rats
Signal Transduction - physiology
Tetradecanoylphorbol Acetate - pharmacology
Transfection
Tumor Cells, Cultured
Citations: Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:During the assembly of gap junctions, a hemichannel in the plasma membrane of one cell is thought to align and dock with another in an apposed membrane to form a cell-to-cell channel. We report here on the existence and properties of nonjunctional, plasma membrane connexin43 (Cx43) hemichannels. The opening of the hemichannels was demonstrated by the cellular uptake of 5(6)-carboxyfluorescein from the culture medium when extracellular calcium levels were reduced. Dye uptake exhibited properties similar to those of gap junction channels. For example, using different dyes, the levels of uptake were correlated with molecular size: 5(6)-carboxyfluorescein (∼32%), 7-hydroxycoumarin-3-carboxylic acid (∼24%), fura-2 (∼11%), and fluorescein-dextran (∼0.4%). Octanol and heptanol also reduced dye uptake by ∼50%. Detailed analysis of one clone of Novikoff cells transfected with a Cx43 antisense expression vector revealed a reduction in dye uptake levels according to uptake assays and a corresponding decrease in intercellular dye transfer rates in microinjection experiments. In addition, a more limited decrease in membrane resistance upon reduction of extracellular calcium was detected in electrophysiological studies of antisense transfectants, in contrast to control cells. Studies of dye uptake in HeLa cells also demonstrated a large increase following transfection with Cx43. Together these observations indicate that Cx43 is responsible for the hemichannel function in these cultured cells. Similar dye uptake results were obtained with normal rat kidney (NRK) cells, which express Cx43. Dye uptake can be dramatically inhibited by 12-O-tetradeconylphorbol-13-acetate-activated protein kinase C in these cell systems and by a temperature-sensitive tyrosine protein kinase, pp60v-srcin LA25-NRK cells. We conclude that Cx43 hemichannels are found in the plasma membrane, where they are regulated by multiple signaling pathways, and likely represent an important stage in gap junction assembly.
ISSN:0021-9525
1540-8140
DOI:10.1083/jcb.134.4.1019