Crosstalk and epithelial ion transport.
Coordination of ion transport through channels, pumps, exchangers, and cotransporters (or crosstalk) is essential in preserving homeostasis of cell volume and ionic activities while maintaining an adapted response to fluctuations in hormonal and environmental challenges. Crosstalk in epithelia is a concerted action of multiple cytosolic and membrane-bound ion transport regulators. Some of the most likely candidates as crosstalk signals include Ca2+, pH, G protein, actin filaments, protein kinases, ATP, and membrane shuttling. An integrated view of the interaction and convergence of multiple signal pathways on single ion channels is one of the major challenges in membrane transport physiology. Simultaneous measurements of changes in the activity of putative signals and of ion transport rates at the macroscopic and single channel level provide insights into crosstalk phenomena. This measurement is made possible by combining short-circuit current and single channel patch-clamp recording with single cell spectrofluorescence in intact epithelia. In a wide range of Na(+)-absorbing epithelia, there is evidence that small variations in intracellular pH and Ca2+ can simultaneously regulate the activity of Na+ and K+ channels. Crosstalk between the Na/K pump and K+ transport may be mediated by physiologically relevant changes in the ratio ATP:ADP.
Harvey
B J
BJ
Department of Physiology, University College Cork, Ireland.
D000244:Adenosine Diphosphate / Q000502:physiology; D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000502:physiology; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism*; D006801:Humans; D007477:Ions; D019831:Sodium-Calcium Exchanger; D017923:Sodium-Hydrogen Exchangers / Q000502:physiology
D002352:Carrier Proteins; D007477:Ions; D019831:Sodium-Calcium Exchanger; D017923:Sodium-Hydrogen Exchangers; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate