G-protein dependent potentiation of calcium release from sarcoplasmic reticulum of skeletal muscle.
Skinned fibre experiments were conducted to determine if guanine nucleotide-binding proteins play a role in excitation-contraction coupling of skeletal muscle. By itself, the GTP-gamma S, a non hydrolysable GTP analogue was unable to induce calcium release from the sarcoplasmic reticulum, even at concentrations as high as 500 microM. However, calcium- or caffeine-induced calcium releases were enhanced by GTP-gamma S in micromolar concentrations. This response was blocked by GDP-beta S or Pertussis toxin. 32P-ADP-ribosylation catalysed by Pertussis toxin, radiolabelled G-protein alpha subunits in the range of 40 kDa on membrane subcellular fractions of rat skeletal muscle. Using Western blot analysis with antibodies raised against the bovine transducin, G-proteins were identified in frog and rat skeletal muscle subcellular fractions. In most of the muscle fractions (plasma membrane, T-tubules, triads, sarcoplasmic reticulum), the anti-beta subunit antibodies recognized a 36 kDa protein which comigrated with transducin beta subunit. It appears therefore that some of the G-proteins identified by ADP-ribosylation or immunostaining in several subcellular fractions from skeletal muscle, are implicated in the modulation of calcium release from sarcoplasmic reticulum. These results suggest that a Pertussis toxin sensitive G-protein is present at the loci of E-C coupling, and that it serves to regulate the calcium release.
Villaz
M
M
Laboratoire de Biophysique Moléculaire et Cellulaire, Grenoble, France.
Robert
M
M
Carrier
L
L
Beeler
T
T
Rouot
B
B
Toutant
M
M
Dupont
Y
Y
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D019204:GTP-Binding Proteins / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D015151:Immunoblotting; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009132:Muscles / Q000378:metabolism*; D037342:Pertussis Toxin; D011893:Rana esculenta; D051381:Rats; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D013873:Thionucleotides / Q000494:pharmacology; D015293:Transducin / Q000032:analysis; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; D006153:Guanosine Diphosphate; D000246:Adenosine Diphosphate Ribose; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002110:Caffeine; C023427:guanosine 5'-O-(2-thiodiphosphate); D006160:Guanosine Triphosphate; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D015293:Transducin; D002118:Calcium