scholarly journals Membrane-Delimited Phosphorylation Enables the Activation of the Outward-Rectifying K Channels in Motor Cell Protoplasts of Samanea saman

1996 ◽  
Vol 111 (4) ◽  
pp. 1281-1292 ◽  
Author(s):  
N. Moran
Keyword(s):  
K Channels ◽  
Samanea Saman

scholarly journals Regulation by Light of Plant Potassium Uptake through K Channels: Biochemical, Physiological and Biophysical Study

1995 ◽  
Author(s):  
Nava Moran ◽  
Richard Crain ◽  
Wolf-Dieter Reiter
Keyword(s):  
Patch Clamp ◽  
Red Light ◽  
Cell Types ◽  
Cell Swelling ◽  
Signaling Cascade ◽  
Patch Clamp Recording ◽  
Independent Manner ◽  
K Channels ◽  
Biophysical Study ◽  
Samanea Saman

The swelling of plant motor cells is regulated by various signals with almost unknown mediators. One of the obligatory steps in the signaling cascade is the activation of K+-influx channels -K+ channels activated by hyperpolarization (KH channels). We thus explored the regulation of these channels in our model system, motor cell protoplasts from Samanea saman, using patch-clamp in the "whole cell" configuration. (a) The most novel finding was that the activity of KH channels in situ varied with the time of the day, in positive correlation with cell swelling: in Extensor cells KH channels were active in the earlier part of the day, while in Flexor cells only during the later part of the day; (b) High internal pH promoted the activity of these channels in Extensor cells, opposite to the behavior of the equivalent channels in guard cells, but in conformity with the predicted behavior of the putative KH channel, cloned from S. saman recently; (c) HIgh external K+ concentration increased (KH channel currents in Flexor cells. BL depolarized the Flexor cells, as detected in cell-attached patch-clamp recording, using KD channels (the K+-efflux channels) as "voltage-sensing devices". Subsequent Red-Light (RL) pulse followed by Darkness, hyperpolarized the cell. We attribute these changes to the inhibition of the H+-pump by BL and its reactivation by RL, as they were abolished by an H+-pump inhibitor. BL increased also the activity KD channels, in a voltage-independent manner - in all probability by an independent signaling pathway. Blue-Light (BL), which stimulates shrinking of Flexor cells, evoked the IP3 signaling cascade (detected directly by IP3 binding assay), known to mobilize cytosolic Ca2+. Nevertheless, cytosolic Ca2+ . did not activate the KD channel in excised, inside-out patches. In this study we established a close functional similarity of the KD channels between Flexor and Extensior cells. Thus the differences in their responses must stem from different links to signaling in both cell types.

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