GTPγS removal of D-600 block of skeletal muscle excitation-contraction coupling

Lisa C Anderson, LaDora V Thompson, Daniel A. Huetteman, Sue K. Donaldson

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

G proteins interacting with dihydropyridine receptors (DHPR) in transverse tubules (TT) of skeletal muscle may have a role in skeletal excitation-contraction (EC) coupling. The aim of this study was to determine the effects of G protein-specific nucleotides [guanosine 5'-O-(3- thiotriphosphate) (GTPγS) and guanosine 5'-O-(2-thiodiphosphate) (GDPβS)] on the EC coupling mechanism in the presence of D-600, an agent that blocks EC coupling by immobilizing the voltages-sensing subunit of the DHPR in its inactivated state. By use of the mechanically peeled single-fiber preparation from rabbit adductor magnus skeletal muscle, 50 μM GTPγS and 500 μM GDPβS were applied with the fiber in a D-600-induced state of blocked EC coupling. Neither nucleotide served as an independent stimulus for sarcoplasmic reticulum (SR) Ca2+ release when added to the TT polarizing bath under conditions of D-600 block. The presence of GTPγS or GDPβS during a complete EC coupling cycle removed the D-600 block of EC coupling, despite continuous bath D-600. After the nucleotides were washed out, in the continued presence of D-600, the D-600 block of EC coupling was reestablished. In contrast, GTPγS added only during the period of TT depolarization under D-600 block did not remove the D-600 block of EC coupling, even though GTPγS did stimulate SR Ca2+ release. GTPγS had no effect on submaximum (0.5-1.0 mM) caffeine contractures and thus is unlikely to be acting through the Ca2+- induced Ca2+ release mechanism of the SR. These data suggest that the molecular binding site for GTPγS and GDPβS is likely to be in the TT near the DHPR, perhaps on a G protein.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Cell Physiology
Volume272
Issue number2 41-2
StatePublished - Feb 1 1997

Fingerprint

Gallopamil
Excitation Contraction Coupling
Muscle Contraction
Skeletal Muscle
L-Type Calcium Channels
Sarcoplasmic Reticulum
GTP-Binding Proteins
Nucleotides
Baths
Guanosine 5'-O-(3-Thiotriphosphate)
Contracture
Caffeine
Binding Sites
Rabbits

Keywords

  • G proteins
  • depolarization-induced tension
  • peeled skeletal muscle fibers
  • sarcoplasmic reticulum calcium release

Cite this

GTPγS removal of D-600 block of skeletal muscle excitation-contraction coupling. / Anderson, Lisa C; Thompson, LaDora V; Huetteman, Daniel A.; Donaldson, Sue K.

In: American Journal of Physiology - Cell Physiology, Vol. 272, No. 2 41-2, 01.02.1997.

Research output: Contribution to journalArticle

Anderson, Lisa C ; Thompson, LaDora V ; Huetteman, Daniel A. ; Donaldson, Sue K. / GTPγS removal of D-600 block of skeletal muscle excitation-contraction coupling. In: American Journal of Physiology - Cell Physiology. 1997 ; Vol. 272, No. 2 41-2.
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