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© The Rockefeller University Press, 0021-9525/2000//1063 $5.00
The Journal of Cell Biology, Volume 148, Number 5, , 2000 1063-1074

Original Article

Physiological Role of Gap-Junctional Hemichannels

: Extracellular Calcium-Dependent Isosmotic Volume Regulation



Arjan Pieter Quista, Seung Keun Rheea,b, Hai Lina, and Ratneshwar Lala

a Neuroscience Research Institute, University of California, Santa Barbara, California 93106
b Department of Biochemistry, Yeungnam University, Kyongsan, 712-749, Korea
Neuroscience Research Institute, University of California, Santa Barbara, CA 93106.805-893-2005805-893-2350

rlal{at}physics.ucsb.edu

Hemichannels in the overlapping regions of apposing cells plasma membranes join to form gap junctions and provide an intercellular communication pathway. Hemichannels are also present in the nonjunctional regions of individual cells and their activity is gated by several agents, including calcium. However, their physiological roles are unknown. Using techniques of atomic force microscopy (AFM), fluorescent dye uptake assay, and laser confocal immunofluorescence imaging, we have examined the extracellular calcium-dependent modulation of cell volume. In response to a change in the extracellular physiological calcium concentration (1.8 to ≤1.6 mM) in an otherwise isosmotic condition, real-time AFM imaging revealed a significant and reversible increase in the volume of cells expressing gap-junctional proteins (connexins). Volume change did not occur in cells that were not expressing connexins. However, after the transient or stable transfection of connexin43, volume change did occur. The volume increase was accompanied by cytochalasin D-sensitive higher cell stiffness, which helped maintain cell integrity. These cellular physical changes were prevented by gap-junctional blockers, oleamide and β-glycyrrhetinic acid, or were reversed by returning extracellular calcium to the normal level. We conclude that nongap-junctional hemichannels regulate cell volume in response to the change in extracellular physiological calcium in an otherwise isosmotic situation.

Key Words: cell–cell communication • atomic force microscopy • scanning probe microscopy • connexin43 • connexons

© 2000 The Rockefeller University Press

Drs. Quist, Rhee, and Lin contributed equally to this work.

Abbreviations used in this paper: βGCA, β-glycyrrhetinic acid; AFM, atomic force microscopy; Cx43, connexin43; dOG, 2-deoxyglucose; FCCP, carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazine; LY, Lucifer yellow dye; MI, metabolic inhibitor.


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