Excitation-contraction (E-C) coupling is thought to involve close interactions between the calcium release channel (ryanodine receptor; RyR) of the sarcoplasmic reticulum (SR) and the dihydropyridine receptor (DHPR) alpha 1 subunit in the T-tubule membrane. Triadin, a 95-kD protein isolated from heavy SR, binds both the RyR and DHPR and may thus participate in E-C coupling or in interactions responsible for the formation of SR/T-tubule junctions. Immunofluorescence labeling of normal mouse myotubes shows that the RyR and triadin co-aggregate with the DHPR in punctate clusters upon formation of functional junctions. Dysgenic myotubes with a deficiency in the alpha 1 subunit of the DHPR show reduced expression and clustering of RyR and triadin; however, both proteins are still capable of forming clusters and attaining mature cross-striated distributions. Thus, the molecular organization of the RyR and triadin in the terminal cisternae of SR as well as its association with the T-tubules are independent of interactions with the DHPR alpha 1 subunit. Analysis of calcium transients in dysgenic myotubes with fluorescent calcium indicators reveals spontaneous and caffeine-induced calcium release from intracellular stores similar to those of normal muscle; however, depolarization-induced calcium release is absent. Thus, characteristic calcium release properties of the RyR do not require interactions with the DHPR; neither do they require the normal organization of the RyR in the terminal SR cisternae. In hybrids of dysgenic myotubes fused with normal cells, both action potential-induced calcium transients and the normal clustered organization of the RyR are restored in regions expressing the DHPR alpha 1 subunit.
Skip Nav Destination
Article navigation
1 December 1993
Article|
December 01 1993
Triad formation: organization and function of the sarcoplasmic reticulum calcium release channel and triadin in normal and dysgenic muscle in vitro.
B E Flucher,
B E Flucher
Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Search for other works by this author on:
S B Andrews,
S B Andrews
Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Search for other works by this author on:
S Fleischer,
S Fleischer
Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Search for other works by this author on:
A R Marks,
A R Marks
Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Search for other works by this author on:
A Caswell,
A Caswell
Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Search for other works by this author on:
J A Powell
J A Powell
Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Search for other works by this author on:
B E Flucher
Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
S B Andrews
Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
S Fleischer
Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
A R Marks
Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
A Caswell
Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
J A Powell
Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1993) 123 (5): 1161–1174.
Citation
B E Flucher, S B Andrews, S Fleischer, A R Marks, A Caswell, J A Powell; Triad formation: organization and function of the sarcoplasmic reticulum calcium release channel and triadin in normal and dysgenic muscle in vitro.. J Cell Biol 1 December 1993; 123 (5): 1161–1174. doi: https://doi.org/10.1083/jcb.123.5.1161
Download citation file:
Sign in
Don't already have an account? Register
Client Account
You could not be signed in. Please check your email address / username and password and try again.
Could not validate captcha. Please try again.
Sign in via your Institution
Sign in via your InstitutionSuggested Content
Email alerts
Advertisement
Advertisement