The distal C terminus of the dihydropyridine receptor ß1a subunit is essential for tetrad formation in skeletal muscle.
Proc Natl Acad Sci U S A
; 119(19): e2201136119, 2022 05 10.
Article
en En
| MEDLINE
| ID: mdl-35507876
ABSTRACT
The skeletal muscle dihydropyridine receptor (DHPR) ß1a subunit is indispensable for full trafficking of DHPRs into triadic junctions (i.e., the close apposition of transverse tubules and sarcoplasmic reticulum [SR]), facilitation of DHPRα1S voltage sensing, and arrangement of DHPRs into tetrads as a consequence of their interaction with ryanodine receptor (RyR1) homotetramers. These three features are obligatory for skeletal muscle excitationcontraction (EC) coupling. Previously, we showed that all four vertebrate ß isoforms (ß1ß4) facilitate α1S triad targeting and, except for ß3, fully enable DHPRα1S voltage sensing [Dayal et al., Proc. Natl. Acad. Sci. U.S.A. 110, 74887493 (2013)]. Consequently, ß3 failed to restore EC coupling despite the fact that both ß3 and ß1a restore tetrads. Thus, all ß-subunits are able to restore triad targeting, but only ß1a restores both tetrads and proper DHPRRyR1 coupling [Dayal et al., Proc. Natl. Acad. Sci. U.S.A. 110, 74887493 (2013)]. To investigate the molecular region(s) of ß1a responsible for the tetradic arrangement of DHPRs and thus DHPRRyR1 coupling, we expressed loss- and gain-of-function chimeras between ß1a and ß4, with systematically swapped domains in zebrafish strain relaxed (ß1-null) for patch clamp, cytoplasmic Ca2+ transients, motility, and freeze-fracture electron microscopy. ß1a/ß4 chimeras with either N terminus, SH3, HOOK, or GK domain derived from ß4 showed complete restoration of SR Ca2+ release. However, chimera ß1a/ß4(C) with ß4 C terminus produced significantly reduced cytoplasmic Ca2+ transients. Conversely, gain-of-function chimera ß4/ß1a(C) with ß1a C terminus completely restored cytoplasmic Ca2+ transients, DHPR tetrads, and motility. Furthermore, we found that the nonconserved, distal C terminus of ß1a plays a pivotal role in reconstitution of DHPR tetrads and thus allosteric DHPRRyR1 interaction, essential for skeletal muscle EC coupling.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Fibras Musculares Esqueléticas
/
Canal Liberador de Calcio Receptor de Rianodina
/
Canales de Calcio Tipo L
Límite:
Animals
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Año:
2022
Tipo del documento:
Article
País de afiliación:
Austria