A Polybasic Plasma Membrane Binding Motif in the I-II Linker Stabilizes Voltage-gated CaV1.2 Calcium Channel Function.
Bottom Line: Neutralization of four arginine residues eliminated plasma membrane binding.Patch clamp recordings revealed facilitated opening of Cav1.2 channels containing these mutations, weaker inhibition by phospholipase C activation, and reduced expression of channels (as quantified by ON-gating charge) at the plasma membrane.Our data provide new evidence for a membrane binding motif within the I-II linker of LTCC α1-subunits essential for stabilizing normal Ca(2+) channel function.
Affiliation: From the Institute of Pharmacy, Department of Pharmacology and Toxicology, and Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria.Show MeSH
Related in: MedlinePlus
Mentions: To further identify the structural motif within the linker responsible for membrane targeting we expressed triple-FLAG-labeled linker peptides with deletions of equal size (29–30 amino acids) located in different parts of the CaV1.2 linker (Fig. 2A). The I-II linker of CaV1.2 was chosen for this analysis because it provided the best signal/noise ratio (not shown). Whereas membrane binding of mutants Δ436–465, Δ466–495, and Δ496–525 remained unaffected by the deletions (Fig. 2B), removal of amino acids 526–554 (Fig. 2, A and B; Δ526–554) abolished plasma membrane binding and resulted in cytoplasmic staining. Accordingly, mutants Δ436–465 and Δ496–525 translocated co-expressed C3S/C4Sβ2a to the plasma membrane (Fig. 2B), whereas Δ526–554 did not (Fig. 2B). Mutant Δ466–495 failed to target C3S/C4Sβ2a to the plasma membrane (Fig. 2B). This was expected, because the β-subunit α1-subunit interaction domain (AID) is also removed by this deletion. By creating additional deletion mutants Δ536–554 (no membrane binding; Fig. 3A) and Δ544–554 (membrane-bound; Fig. 3A) we found that essential structural determinants for membrane targeting must be localized within positions 536–543 (Fig. 2A).
Affiliation: From the Institute of Pharmacy, Department of Pharmacology and Toxicology, and Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria.