title: Calsequestrin is essential for the Ca2+ release induced by myotoxin alpha in skeletal muscle sarcoplasmic reticulum.
abstract: Myotoxin alpha (MYTX), a polypeptide toxin purified from the venom of prairie rattlesnakes (Crotalus viridis viridis), induced Ca2+ release from the heavy fraction of skeletal sarcoplasmic reticulum (HSR), using a Ca2+ electrode. The effect of MYTX was nearly abolished by pretreatment with ryanodine, an alkaloid-based Ca2+ channel blocker. In the stopped-flow experiments, MYTX increased the choline+ permeability of HSR in the presence of calsequestrin (CS). Single channel recording experiments showed that in the presence of CS, the channel currents were markedly enhanced by MYTX applied to the cis side, but not to the trans side. However, in the absence of CS, MYTX failed to cause the excitatory effect in both the experiments. These results suggest that CS is essential for MYTX-induced Ca2+ release through the Ca2+ release channels in skeletal HSR.
authors.affiliation: Department of Pharmaceutical Molecular Biology, Tohoku University, Sendai, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Ohkura
authors.forename: T
authors.initials: T
authors.lastname: Ide
authors.forename: K
authors.initials: K
authors.lastname: Furukawa
authors.forename: T
authors.initials: T
authors.lastname: Kawasaki
authors.forename: M
authors.initials: M
authors.lastname: Kasai
authors.forename: Y
authors.initials: Y
authors.lastname: Ohizumi
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002155:Calsequestrin / Q000494:pharmacology* / Q000502:physiology*; D003435:Crotalid Venoms / Q000633:toxicity*; D018482:Muscle, Skeletal / Q000187:drug effects*; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000187:drug effects*; D013997:Time Factors
chemical_list: D002155:Calsequestrin; D003435:Crotalid Venoms; C018932:myotoxin A; D000255:Adenosine Triphosphate; D002118:Calcium