A spontaneously occurring or electrically elicited hyperpolarizing activation (HA) in L cells was previously shown to be due to a specific increase in the membrane K+ permeability (Nelson et at. 1972. J. Gen. Physiol. 60:58--71). Intracellular injection of Ca++ elicits an identical hyperpolarizing response which suggests that the increased K+ permeability associated with the HA is mediated by a...

Many regulatory steps precede final membrane fusion in neuroendocrine cells. Some parts of this preparatory cascade, including fusion and priming, are dependent on the intracellular Ca(2+) concentration ([Ca(2+)](i)). However, the functional implications of [Ca(2+)](i) in the regulation of docking remain elusive and controversial due to an inability to determine the modulatory effect of [Ca(2+)...

The mitochondrial permeability transition (MPT) is implicated in cardiac reperfusion/reoxygenation injury. In isolated ventricular myocytes, the sulfhydryl (SH) group modifier and MPT inducer phenylarsine oxide (PAO) caused MPT, severe hypercontracture, and irreversible membrane injury associated with increased cytoplasmic free [Ca(2+)]. Removal of extracellular Ca(2+) or depletion of nonmitoch...

Herrera, Gerald M., Thomas J. Heppner, and Mark T. Nelson. Voltage dependence of the coupling of Ca sparks to BKCa channels in urinary bladder smooth muscle. Am J Physiol Cell Physiol 280: C481–C490, 2001.—Large-conductance Cadependent K (BKCa) channels play a critical role in regulating urinary bladder smooth muscle (UBSM) excitability and contractility. Measurements of BKCa currents and intra...

This study examined the mechanism by which amiloride dissociates Na and Ca transport in distal convoluted tubules. Control rates of Na uptake averaged 288 nmol/(min mg protein) and were inhibited 39% by microM amiloride. Amiloride had no effect on Cl uptake. Resting membrane voltage, measured with the voltage-sensitive dye DiOC6 (3), averaged -70 mV. Amiloride hyperpolarized cells in a reversib...

Organelles are in constant communication with each other through exchange of proteins (mediated by trafficking vesicles) and lipids [mediated by both trafficking vesicles and lipid transfer proteins (LTPs)]. It has long been known that vesicle trafficking can be tightly regulated by the second messenger Ca(2+), allowing membrane protein transport to be adjusted according to physiological demand...

The Entamoeba histolytica upstream regulatory element 3-binding protein (URE3-BP) is a transcription factor that binds DNA in a Ca(2+)-inhibitable manner. The protein is located in both the nucleus and the cytoplasm but has also been found to be enriched in the plasma membrane of amebic trophozoites. We investigated the reason for the unusual localization of URE3-BP at the amebic plasma membran...

We have determined the DNA sequence of the gene encoding the protein of the plasma membrane Ca(2+)-ATPase in Paramecium tetraurelia. The predicted amino acid sequence of the plasma membrane Ca(2+)-ATPase shows homology to conserved regions of known plasma membrane Ca(2+)-ATPases and contains the known binding sites for ATP (FITC), acylphosphate formation, and calmodulin, as well as the "hinge" ...

Synaptotagmin 1 (Syt1), a major Ca(2+) sensor in neuroexocytosis, utilizes SNARE- and membrane-binding to regulate vesicle fusion, a required process for neurotransmitter release at the synapse. However, the mechanism by which Syt1 orchestrates SNARE- and membrane- binding to control individual vesicle fusion steps is still unclear. In this study, we used a number of single vesicle assays that ...

The oscillatory [Ca(2+)](i) signals typically seen following physiologically relevant stimulation of phospholipase C-linked receptors are associated with a receptor-activated entry of Ca(2+), which plays a critical role in driving the oscillations and influencing their frequency. We have recently shown that this receptor-activated entry of Ca(2+) does not conform to the widely accepted "capacit...