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Cover Caption:
Cover:
Diagram of a general model depicting several potential subcellular mechanisms by which KCl may cause Ca2+
sensitization (?s indicate some alternative hypotheses proposed in the literature). Increased [Ca2+]i produced upon
membrane depolarization with KCl may cause Rho kinase (ROK) translocation to caveolin within distinct plasma
membrane domains, such as caveolae or the dystroglycan complex, where RhoA-GTP or arachidonic acid activates ROK
(ROK*). How ROK is translocated from the cytosol to plasma membrane sites is not known, but one possible mode of
transport is as cargo carried on actin or tubulin cables. Membrane depolarization rather than increases in [Ca2+]i may be
responsible for activation of ROK, but the molecular mechanism linking depolarization with ROK activation remains to be
determined. Because G protein-coupled receptors (GPCRs) and KCl can both cause membrane depolarization and elevate
[Ca2+]i, KCl-induced Ca2+ sensitization may represent a subset of GPCR-induced Ca2+ sensitization. Elevations in [Ca2+]i
can also activate Ca2+/calmodulin-dependent protein kinase and ERK, which may alter myosin light chain kinase activity.
To ensure that KCl-induced Ca2+ sensitization is due solely to increases in [Ca2+]i or membrane depolarization, the
potential contribution of paracrine and autocrine agents that may cause Ca2+ sensitization by activation of GPCRs must be
eliminated. See related article by Ratz PH, Berg KM, Urban NH, and Miner AS.
Am J Physiol Cell Physiol 288: C769–C783, 2005.
Copyright © 2005 by the American Physiological Society.
