Different pathways for activation and deactivation in CaV1.2: a minimal gating model.
Point mutations in pore-lining S6 segments of CaV1.2 shift the voltage dependence of activation into the hyperpolarizing direction and significantly decelerate current activation and deactivation. Here, we analyze theses changes in channel gating in terms of a circular four-state model accounting for an activation R-A-O and a deactivation O-D-R pathway. Transitions between resting-closed (R) and activated-closed (A) states (rate constants x(V) and y(V)) and open (O) and deactivated-open (D) states (u(V) and w(V)) describe voltage-dependent sensor movements. Voltage-independent pore openings and closures during activation (A-O) and deactivation (D-R) are described by rate constants alpha and beta, and gamma and delta, respectively. Rate constants were determined for 16-channel constructs assuming that pore mutations in IIS6 do not affect the activating transition of the voltage-sensing machinery (x(V) and y(V)). Estimated model parameters of 15 CaV1.2 constructs well describe the activation and deactivation processes. Voltage dependence of the "pore-releasing" sensor movement ((x(V)) was much weaker than the voltage dependence of "pore-locking" sensor movement (y(V)). Our data suggest that changes in membrane voltage are more efficient in closing than in opening CaV1.2. The model failed to reproduce current kinetics of mutation A780P that was, however, accurately fitted with individually adjusted x(V) and y(V). We speculate that structural changes induced by a proline substitution in this position may disturb the voltage-sensing domain.
Beyl
Stanislav
S
Department of Pharmacology and Toxicology, University of Vienna, 1090 Vienna, Austria.
Kügler
Philipp
P
Kudrnac
Michaela
M
Hohaus
Annette
A
Hering
Steffen
S
Timin
Eugen
E
D020746:Calcium Channels, L-Type / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D005998:Glycine / Q000235:genetics; D006801:Humans; D015640:Ion Channel Gating; D008956:Models, Chemical; D009154:Mutation; D018408:Patch-Clamp Techniques; D011487:Protein Conformation
D020746:Calcium Channels, L-Type; C419385:L-type calcium channel alpha(1C); D005998:Glycine
Nature. 2002 May 30;417(6888):515-22
12037559
Proc Natl Acad Sci U S A. 2005 May 24;102(21):7553-8
15897456
J Biol Chem. 2009 May 1;284(18):12276-84
19265197
Cell. 2002 Oct 18;111(2):231-9
12408867
J Gen Physiol. 2005 Nov;126(5):413-7
16260835
Neuron. 2004 Mar 25;41(6):859-65
15046719
J Gen Physiol. 1992 Mar;99(3):367-90
1316936
Nature. 2003 May 1;423(6935):33-41
12721618
Proc Natl Acad Sci U S A. 1998 Feb 17;95(4):1903-8
9465115
Science. 1998 Apr 3;280(5360):69-77
9525859
Science. 2005 Aug 5;309(5736):897-903
16002581
Annu Rev Cell Dev Biol. 2006;22:23-52
16704338
J Biol Chem. 2006 Dec 22;281(51):39424-36
17038321
Annu Rev Cell Dev Biol. 2000;16:521-55
11031246
Channels (Austin). 2008 May-Jun;2(3):216-23
18836301
J Biol Chem. 2005 Nov 18;280(46):38471-7
16157588
Gene. 1989 Apr 15;77(1):61-8
2744488
J Mol Biol. 2002 Nov 8;323(5):951-60
12417206
Pflugers Arch. 1981 Aug;391(2):85-100
6270629
Nature. 2001 Nov 1;414(6859):43-8
11689936
Channels (Austin). 2008 Mar-Apr;2(2):61-9
18849656
J Physiol. 1952 Aug;117(4):500-44
12991237
J Gen Physiol. 1994 Feb;103(2):321-62
8189208
J Gen Physiol. 1994 Feb;103(2):279-319
8189207
Prog Biophys Mol Biol. 2001;75(3):165-99
11376798
J Mol Biol. 1988 Jun 5;201(3):601-19
3418712