TY - JOUR
T1 - Actin modifies Ca2+ block of epithelial Na+ channels in planar lipid bilayers
AU - Berdiev, Bakhrom K.
AU - Latorre, Ramon
AU - Benos, Dale J.
AU - Ismailov, Iskander I.
N1 - Funding Information:
This work was supported by National Institutes of Health Grants DK37206 and DK56095 (D.J.B.), and the grants FONDECYT 100-0890 (R.L.) and Cátedra Presidencial, a Human Frontier in Science Program grant (R.L.), and by a group of Chilean companies (AFP Protection, CODELCO, Empresas CMPC, CGE, Gener S.A., Minera Escondida, Minera Collahuasi, NOVAGAS, Business Design Assoc., and XEROX Chile) (R.L.). The Centro de Estudios Cientificos is a Millenium Science Institute.
PY - 2001
Y1 - 2001
N2 - The mechanism by which the cytoskeletal protein actin affects the conductance of amiloride-sensitive epithelial sodium channels (ENaC) was studied in planar lipid bilayers. In the presence of monomeric actin, we found a decrease in the single-channel conductance of α-ENaC that did not occur when the internal [Ca2+]free was buffered to <10 nM. An analysis of single-channel kinetics demonstrated that Ca2+ induced the appearance of long-lived closed intervals separating bursts of channel activity, both in the presence and in the absence of actin. In the absence of actin, the duration of these bursts and the time spent by the channel in its open, but not in its short-lived closed state, were inversely proportional to [Ca2+]. This, together with a lengthening of the interburst intervals, translated into a dose-dependent decrease in the single-channel open probability. In contrast, a [Ca2+]-dependent decrease in α-ENaC conductance in the presence of actin was accompanied by lengthening of the burst intervals with no significant changes in the open or closed (both short- and long-lived) times. We conclude that Ca2+ acts as a "fast-to-intermediate" blocker when monomeric actin is present, producing a subsequent attenuation of the apparent unitary conductance of the channel.
AB - The mechanism by which the cytoskeletal protein actin affects the conductance of amiloride-sensitive epithelial sodium channels (ENaC) was studied in planar lipid bilayers. In the presence of monomeric actin, we found a decrease in the single-channel conductance of α-ENaC that did not occur when the internal [Ca2+]free was buffered to <10 nM. An analysis of single-channel kinetics demonstrated that Ca2+ induced the appearance of long-lived closed intervals separating bursts of channel activity, both in the presence and in the absence of actin. In the absence of actin, the duration of these bursts and the time spent by the channel in its open, but not in its short-lived closed state, were inversely proportional to [Ca2+]. This, together with a lengthening of the interburst intervals, translated into a dose-dependent decrease in the single-channel open probability. In contrast, a [Ca2+]-dependent decrease in α-ENaC conductance in the presence of actin was accompanied by lengthening of the burst intervals with no significant changes in the open or closed (both short- and long-lived) times. We conclude that Ca2+ acts as a "fast-to-intermediate" blocker when monomeric actin is present, producing a subsequent attenuation of the apparent unitary conductance of the channel.
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U2 - 10.1016/S0006-3495(01)76190-5
DO - 10.1016/S0006-3495(01)76190-5
M3 - Article
C2 - 11325720
AN - SCOPUS:0034744453
VL - 80
SP - 2176
EP - 2186
JO - Biophysical Journal
JF - Biophysical Journal
SN - 0006-3495
IS - 5
ER -