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Titolo:
A component of excitation-contraction coupling triggered in the absence ofthe T671-L690 and L720-Q765 regions of the II-III loop of the dihydropyridine receptor alpha(1s) pore subunit
Autore:
Ahern, CA; Bhattacharya, D; Mortenson, L; Coronado, R;
Indirizzi:
Univ Wisconsin, Dept Physiol, Sch Med, Madison, WI 53706 USA Univ Wisconsin Madison WI USA 53706 ysiol, Sch Med, Madison, WI 53706 USA
Titolo Testata:
BIOPHYSICAL JOURNAL
fascicolo: 6, volume: 81, anno: 2001,
pagine: 3294 - 3307
SICI:
0006-3495(200112)81:6<3294:ACOECT>2.0.ZU;2-K
Fonte:
ISI
Lingua:
ENG
Soggetto:
SKELETAL-MUSCLE FIBERS; CA2+ RELEASE CHANNELS; RYANODINE RECEPTORS; CHARGE MOVEMENT; CALCIUM-RELEASE; SELECTIVELY DEFICIENT; VOLTAGE SENSOR; ACTIVATION; MYOTUBES; TRANSIENTS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
50
Recensione:
Indirizzi per estratti:
Indirizzo: Coronado, R Univ Wisconsin, Dept Physiol, Sch Med, 1300 Univ Ave, Madison,WI 53706 USA Univ Wisconsin 1300 Univ Ave Madison WI USA 53706 WI 53706 USA
Citazione:
C.A. Ahern et al., "A component of excitation-contraction coupling triggered in the absence ofthe T671-L690 and L720-Q765 regions of the II-III loop of the dihydropyridine receptor alpha(1s) pore subunit", BIOPHYS J, 81(6), 2001, pp. 3294-3307

Abstract

We conducted a deletion analysis of two regions identified in the II-III loop of alpha (1S) residues 671-690, which were shown to bind to ryanodine receptor type 1 (RyR1) and stimulate RyR1 channels in vitro, and residues 720-765 or the narrower 724-743 region, which confer excitation-contraction (EC) coupling function to chimeric dihydropyridine receptors (DHPRs). Deletion mutants were expressed in dysgenic als-null myotubes and analyzed by voltage-clamp and confocal fluo-4 fluorescence. Immunostaining of the mutant subunits using an N-terminus tag revealed abundant protein expression in allcases. Furthermore, the maximum recovered charge movement density was > 80% of that recovered by full-length als in all cases. Delta 671-690 had no effect on the magnitude of voltage-evoked Ca2+ transients or the L-type Ca2current density. In contrast, Delta 720-765 or Delta 724-743 abolished Ca2 transients entirely, and L-type Ca2+ current was reduced or absent. Surprisingly, Ca2+ transients and Ca2+ currents of a moderate magnitude were recovered by the double deletion mutant Delta 671-690/Delta 720-765. A simple explanation for this result is that Delta 720-765 induces a conformation change that disrupts EC coupling, and this conformational change is partiallyreverted by Delta 671-690. To test for Ca 21 -entry independent EC coupling, a pore mutation (E1014K) known to entirely abolish the inward Ca 21 current was introduced. a,, Delta 671-690/Delta 720-765/ E1014K expressed Ca2+ transients with Boltzmann parameters identical to those of the Ca2+-conducting double deletion construct. The data strongly suggest that skeletal-typeEC coupling is not uniquely controlled by alpha (1S) 720-765. Other regions of alpha (1S) or other DHPR subunits must therefore directly contribute to the activation of RyR1 during EC coupling.

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Documento generato il 10/07/20 alle ore 19:08:05