|
|
|
|
|
|
|
||
ARTICLE |
Correspondence to Richard S. Lewis or Murali Prakriya: rslewis{at}stanford.edu; m-prakriya{at}northwestern.edu
CRAC (calcium release-activated Ca2+) channels attain an extremely high selectivity for Ca2+ from the blockade of monovalent cation permeation by Ca2+ within the pore. In this study we have exploited the blockade by Ca2+ to examine the size of the CRAC channel pore, its unitary conductance for monovalent cations, and channel gating properties. The permeation of a series of methylammonium compounds under divalent cation-free conditions indicates a minimum pore diameter of 3.9 Å. Extracellular Ca2+ blocks monovalent flux in a manner consistent with a single intrapore site having an effective Ki of 20 µM at –110 mV. Block increases with hyperpolarization, but declines below –100 mV, most likely due to permeation of Ca2+. Analysis of monovalent current noise induced by increasing levels of block by extracellular Ca2+ indicates an open probability (Po) of
0.8. By extrapolating the variance/mean current ratio to the condition of full blockade (Po = 0), we estimate a unitary conductance of 0.7 pS for Na+, or three to fourfold higher than previous estimates. Removal of extracellular Ca2+ causes the monovalent current to decline over tens of seconds, a process termed depotentiation. The declining current appears to result from a reduction in the number of active channels without a change in their high open probability. Similarly, low concentrations of 2-APB that enhance ICRAC increase the number of active channels while open probability remains constant. We conclude that the slow regulation of whole-cell CRAC current by store depletion, extracellular Ca2+, and 2-APB involves the stepwise recruitment of silent channels to a high open-probability gating mode.
Abbreviations used in this paper: CDP, Ca2+-dependent potentiation; CRAC, calcium release-activated Ca2+; MIC, Mg2+-inhibited cation; CaV, voltage-gated Ca2+; TG, thapsigargin; ICRAC, CRAC current; DVF, divalent free; Po, open probability; 2-APB, 2-aminoethyldiphenyl borate.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  B. A. McNally, M. Yamashita, A. Engh, and M. Prakriya Structural determinants of ion permeation in CRAC channels PNAS, December 29, 2009; 106(52): 22516 - 22521. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. Scrimgeour, T. Litjens, L. Ma, G. J. Barritt, and G. Y. Rychkov Properties of Orai1 mediated store-operated current depend on the expression levels of STIM1 and Orai1 proteins J. Physiol., June 15, 2009; 587(12): 2903 - 2918. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. Schindl, J. Bergsmann, I. Frischauf, I. Derler, M. Fahrner, M. Muik, R. Fritsch, K. Groschner, and C. Romanin 2-Aminoethoxydiphenyl Borate Alters Selectivity of Orai3 Channels by Increasing Their Pore Size J. Biol. Chem., July 18, 2008; 283(29): 20261 - 20267. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. G. Meuth, S. Bittner, P. Meuth, O. J. Simon, T. Budde, and H. Wiendl TWIK-related Acid-sensitive K+ Channel 1 (TASK1) and TASK3 Critically Influence T Lymphocyte Effector Functions J. Biol. Chem., May 23, 2008; 283(21): 14559 - 14570. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. L. Lewis, K. M. Brundage, R. A. Brundage, and J. B. Barnett 3,4-Dichloropropionanilide (DCPA) Inhibits T-Cell Activation by Altering the Intracellular Calcium Concentration following Store Depletion Toxicol. Sci., May 1, 2008; 103(1): 97 - 107. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W.-C. Chang, J. Di Capite, K. Singaravelu, C. Nelson, V. Halse, and A. B. Parekh Local Ca2+ Influx through Ca2+ Release-activated Ca2+ (CRAC) Channels Stimulates Production of an Intracellular Messenger and an Intercellular Pro-inflammatory Signal J. Biol. Chem., February 22, 2008; 283(8): 4622 - 4631. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Tammaro and F. M. Ashcroft A mutation in the ATP-binding site of the Kir6.2 subunit of the KATP channel alters coupling with the SUR2A subunit J. Physiol., November 1, 2007; 584(3): 743 - 753. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Yamashita, L. Navarro-Borelly, B. A. McNally, and M. Prakriya Orai1 Mutations Alter Ion Permeation and Ca2+-dependent Fast Inactivation of CRAC Channels: Evidence for Coupling of Permeation and Gating J. Gen. Physiol., October 29, 2007; 130(5): 525 - 540. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Z. Li, J. Lu, P. Xu, X. Xie, L. Chen, and T. Xu Mapping the Interacting Domains of STIM1 and Orai1 in Ca2+ Release-activated Ca2+ Channel Activation J. Biol. Chem., October 5, 2007; 282(40): 29448 - 29456. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. I. DeHaven, J. T. Smyth, R. R. Boyles, and J. W. Putney Jr. Calcium Inhibition and Calcium Potentiation of Orai1, Orai2, and Orai3 Calcium Release-activated Calcium Channels J. Biol. Chem., June 15, 2007; 282(24): 17548 - 17556. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Lorin-Nebel, J. Xing, X. Yan, and K. Strange CRAC channel activity in C. elegans is mediated by Orai1 and STIM1 homologues and is essential for ovulation and fertility J. Physiol., April 1, 2007; 580(1): 67 - 85. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Highlights From The Literature Physiology, December 1, 2006; 21(6): 374 - 379. [Full Text] [PDF]
|
|
|
|
