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Disruption of the IS6-AID linker affects voltage-gated calcium channel inactivation and facilitation.

Findeisen F, Minor DL - J. Gen. Physiol. (2009)

Bottom Line: The Ca(V)beta/Ca(V)alpha(1)-I-II loop and Ca(2+)/calmodulin (CaM)/Ca(V)alpha(1)-C-terminal tail complexes have been shown to modulate each, respectively.Nevertheless, how each complex couples to the pore and whether each affects inactivation independently have remained unresolved.Collectively, the data strongly suggest that components traditionally associated solely with VDI, Ca(V)beta and the IS6-AID linker, are essential for calcium-dependent modulation, and that both Ca(V)beta-dependent and CaM-dependent components couple to the pore by a common mechanism requiring Ca(V)beta and an intact IS6-AID linker.

View Article: PubMed Central - PubMed

Affiliation: Cardiovascular Research Institute, Department of Biochemistry and Biophysics, California Institute for Quantitative Biosciences, University of California, San Francisco, CA 94158, USA.

ABSTRACT
Two processes dominate voltage-gated calcium channel (Ca(V)) inactivation: voltage-dependent inactivation (VDI) and calcium-dependent inactivation (CDI). The Ca(V)beta/Ca(V)alpha(1)-I-II loop and Ca(2+)/calmodulin (CaM)/Ca(V)alpha(1)-C-terminal tail complexes have been shown to modulate each, respectively. Nevertheless, how each complex couples to the pore and whether each affects inactivation independently have remained unresolved. Here, we demonstrate that the IS6-alpha-interaction domain (AID) linker provides a rigid connection between the pore and Ca(V)beta/I-II loop complex by showing that IS6-AID linker polyglycine mutations accelerate Ca(V)1.2 (L-type) and Ca(V)2.1 (P/Q-type) VDI. Remarkably, mutations that either break the rigid IS6-AID linker connection or disrupt Ca(V)beta/I-II association sharply decelerate CDI and reduce a second Ca(2+)/CaM/Ca(V)alpha(1)-C-terminal-mediated process known as calcium-dependent facilitation. Collectively, the data strongly suggest that components traditionally associated solely with VDI, Ca(V)beta and the IS6-AID linker, are essential for calcium-dependent modulation, and that both Ca(V)beta-dependent and CaM-dependent components couple to the pore by a common mechanism requiring Ca(V)beta and an intact IS6-AID linker.

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CaVβ isoform rank order VDI effects remain in the presence of disrupted IS6-AID linker. Representative normalized IBa traces for the indicated CaVβ subunits coexpressed with (A) CaV1.2 and (B) CaV1.2 GGG. Note the different timescales. (C) Representative normalized IBa traces for coexpression of CaVβ1 and CaVβ2a with CaV2.1 and CaV2.1 GGG.
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fig3: CaVβ isoform rank order VDI effects remain in the presence of disrupted IS6-AID linker. Representative normalized IBa traces for the indicated CaVβ subunits coexpressed with (A) CaV1.2 and (B) CaV1.2 GGG. Note the different timescales. (C) Representative normalized IBa traces for coexpression of CaVβ1 and CaVβ2a with CaV2.1 and CaV2.1 GGG.

Mentions: Prior studies of VDI rates imparted to CaVα1 subunits by various CaVβ isoforms demonstrated a stereotyped rank order: fastest to slowest, CaVβ1 > CaVβ2b > CaVβ2a (Olcese et al., 1994; Stea et al., 1994; De Waard and Campbell, 1995; Yasuda et al., 2004). Coexpression of CaV1.2 with CaVβ1, CaVβ2b, or CaVβ2a results in VDI that is 3.2- and 1.3-fold faster for CaVβ1 and CaVβ2b relative to CaVβ2a (Fig. 3 A and Table I). Additionally, the mutant subunit ssCaVβ2a (Chien et al., 1996), which lacks the N-terminal palmitoylation that causes CaVβ2a to retard VDI (Chien and Hosey, 1998; Qin et al., 1998; Restituito et al., 2000), displays VDI that is 1.8-fold faster than CaVβ2a and similar to CaVβ2b.


Disruption of the IS6-AID linker affects voltage-gated calcium channel inactivation and facilitation.

Findeisen F, Minor DL - J. Gen. Physiol. (2009)

CaVβ isoform rank order VDI effects remain in the presence of disrupted IS6-AID linker. Representative normalized IBa traces for the indicated CaVβ subunits coexpressed with (A) CaV1.2 and (B) CaV1.2 GGG. Note the different timescales. (C) Representative normalized IBa traces for coexpression of CaVβ1 and CaVβ2a with CaV2.1 and CaV2.1 GGG.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2654080&req=5

fig3: CaVβ isoform rank order VDI effects remain in the presence of disrupted IS6-AID linker. Representative normalized IBa traces for the indicated CaVβ subunits coexpressed with (A) CaV1.2 and (B) CaV1.2 GGG. Note the different timescales. (C) Representative normalized IBa traces for coexpression of CaVβ1 and CaVβ2a with CaV2.1 and CaV2.1 GGG.
Mentions: Prior studies of VDI rates imparted to CaVα1 subunits by various CaVβ isoforms demonstrated a stereotyped rank order: fastest to slowest, CaVβ1 > CaVβ2b > CaVβ2a (Olcese et al., 1994; Stea et al., 1994; De Waard and Campbell, 1995; Yasuda et al., 2004). Coexpression of CaV1.2 with CaVβ1, CaVβ2b, or CaVβ2a results in VDI that is 3.2- and 1.3-fold faster for CaVβ1 and CaVβ2b relative to CaVβ2a (Fig. 3 A and Table I). Additionally, the mutant subunit ssCaVβ2a (Chien et al., 1996), which lacks the N-terminal palmitoylation that causes CaVβ2a to retard VDI (Chien and Hosey, 1998; Qin et al., 1998; Restituito et al., 2000), displays VDI that is 1.8-fold faster than CaVβ2a and similar to CaVβ2b.

Bottom Line: The Ca(V)beta/Ca(V)alpha(1)-I-II loop and Ca(2+)/calmodulin (CaM)/Ca(V)alpha(1)-C-terminal tail complexes have been shown to modulate each, respectively.Nevertheless, how each complex couples to the pore and whether each affects inactivation independently have remained unresolved.Collectively, the data strongly suggest that components traditionally associated solely with VDI, Ca(V)beta and the IS6-AID linker, are essential for calcium-dependent modulation, and that both Ca(V)beta-dependent and CaM-dependent components couple to the pore by a common mechanism requiring Ca(V)beta and an intact IS6-AID linker.

View Article: PubMed Central - PubMed

Affiliation: Cardiovascular Research Institute, Department of Biochemistry and Biophysics, California Institute for Quantitative Biosciences, University of California, San Francisco, CA 94158, USA.

ABSTRACT
Two processes dominate voltage-gated calcium channel (Ca(V)) inactivation: voltage-dependent inactivation (VDI) and calcium-dependent inactivation (CDI). The Ca(V)beta/Ca(V)alpha(1)-I-II loop and Ca(2+)/calmodulin (CaM)/Ca(V)alpha(1)-C-terminal tail complexes have been shown to modulate each, respectively. Nevertheless, how each complex couples to the pore and whether each affects inactivation independently have remained unresolved. Here, we demonstrate that the IS6-alpha-interaction domain (AID) linker provides a rigid connection between the pore and Ca(V)beta/I-II loop complex by showing that IS6-AID linker polyglycine mutations accelerate Ca(V)1.2 (L-type) and Ca(V)2.1 (P/Q-type) VDI. Remarkably, mutations that either break the rigid IS6-AID linker connection or disrupt Ca(V)beta/I-II association sharply decelerate CDI and reduce a second Ca(2+)/CaM/Ca(V)alpha(1)-C-terminal-mediated process known as calcium-dependent facilitation. Collectively, the data strongly suggest that components traditionally associated solely with VDI, Ca(V)beta and the IS6-AID linker, are essential for calcium-dependent modulation, and that both Ca(V)beta-dependent and CaM-dependent components couple to the pore by a common mechanism requiring Ca(V)beta and an intact IS6-AID linker.

Show MeSH
Related in: MedlinePlus