Journal article
Intramembrane charge movements and excitation– contraction coupling expressed by two-domain fragments of the Ca2+ channel
Proceedings of the National Academy of Sciences - PNAS, Vol.98(12), pp.6935-6940
06/05/2001
DOI: 10.1073/pnas.111001898
PMCID: PMC34456
PMID: 11371610
Abstract
To investigate the molecular basis of the voltage sensor that triggers excitation–contraction (EC) coupling, the four-domain pore subunit of the dihydropyridine receptor (DHPR) was cut in the cytoplasmic linker between domains II and III. cDNAs for the I-II domain (α1S 1–670) and the III-IV domain (α1S 701-1873) were expressed in dysgenic α1S-null myotubes. Coexpression of the two fragments resulted in complete recovery of DHPR intramembrane charge movement and voltage-evoked Ca2+ transients. When fragments were expressed separately, EC coupling was not recovered. However, charge movement was detected in the I-II domain expressed alone. Compared with I-II and III-IV together, the charge movement in the I-II domain accounted for about half of the total charge (Qmax = 3 ± 0.23 vs. 5.4 ± 0.76 fC/pF, respectively), and the half-activation potential for charge movement was significantly more negative (V1/2 = 0.2 ± 3.5 vs. 22 ± 3.4 mV, respectively). Thus, interactions between the four internal domains of the pore subunit in the assembled DHPR profoundly affect the voltage dependence of intramembrane charge movement. We also tested a two-domain I-II construct of the neuronal α1A Ca2+ channel. The neuronal I-II domain recovered charge movements like those of the skeletal I-II domain but could not assist the skeletal III-IV domain in the recovery of EC coupling. The results demonstrate that a functional voltage sensor capable of triggering EC coupling in skeletal myotubes can be recovered by the expression of complementary fragments of the DHPR pore subunit. Furthermore, the intrinsic voltage-sensing properties of the α1A I-II domain suggest that this hemi-Ca2+ channel could be relevant to neuronal function.
Details
- Title: Subtitle
- Intramembrane charge movements and excitation– contraction coupling expressed by two-domain fragments of the Ca2+ channel
- Creators
- Chris A Ahern - Department of Physiology, University of Wisconsin School of Medicine, Madison, WI 53706Jyothi Arikkath - Department of Physiology, University of Wisconsin School of Medicine, Madison, WI 53706Paola Vallejo - Department of Physiology, University of Wisconsin School of Medicine, Madison, WI 53706Christina A Gurnett - Department of Physiology, University of Wisconsin School of Medicine, Madison, WI 53706Patricia A Powers - Department of Physiology, University of Wisconsin School of Medicine, Madison, WI 53706Kevin P Campbell - Department of Physiology, University of Wisconsin School of Medicine, Madison, WI 53706Roberto Coronado - Department of Physiology, University of Wisconsin School of Medicine, Madison, WI 53706
- Resource Type
- Journal article
- Publication Details
- Proceedings of the National Academy of Sciences - PNAS, Vol.98(12), pp.6935-6940
- DOI
- 10.1073/pnas.111001898
- PMID
- 11371610
- PMCID
- PMC34456
- NLM abbreviation
- Proc Natl Acad Sci U S A
- ISSN
- 0027-8424
- eISSN
- 1091-6490
- Publisher
- National Academy of Sciences
- Language
- English
- Date published
- 06/05/2001
- Academic Unit
- Neurology; Molecular Physiology and Biophysics; Iowa Neuroscience Institute
- Record Identifier
- 9984020741402771
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