Reactive disulfide compounds induce Ca2+ release from cardiac sarcoplasmic reticulum

Academic Article

Abstract

  • Reactive disulfide compounds (RDSs) with a pyridyl ring adjacent to a disulfide bond, 2,2′dithiodipyridine (2,2′ DTDP) and 4,4′ dithiodipyridine (4,4′ DTDP), induce Ca release from isolated canine cardiac sarcoplasmic reticulum (SR) vesicles. RDSs are absolutely specific to free sulfhydryl (SH) groups and oxidize SH sites of low pK via a thiol-disulfide exchange reaction, with the stoichiometric production of thiopyridone in the medium. As in skeletal SR, this reaction caused large increases in the Ca permeability of cardiac SR and the number of SH sites oxidized by RDSs was kinetically and quantitatively measured through the absorption o f thiopyridone. RDS-induced Ca release from cardiac SR was characterized and compared to the action of RDSs on skeletal SR and to Ca -induced Ca release, (i) RDS-induced Ca release from cardiac SR was dependent on ionized Mg , with maximum rates of release occurring at 0.5 and 1 mm Mg for 2,2′ DTDP and 4,4′ DTDP, respectively, (ii) In the presence of adenine nucleotides (0.1-1 mm), the oxidation of SH sites in cardiac SR by exogenously added RDS was inhibited, which, in turn, inhibited Ca release induced by RDSs. (iii) Conversely, when the oxidation reaction between RDSs and cardiac SR was completed and Ca release pathways were opened, subsequent additions of adenine nucleotides stimulated Ca efflux induced by RDSs. (iv) Sulfhydryl reducing agents (e.g., dithiothreitol, DTT, 1-5 mm) inhibited RDS-induced Ca efflux in a concentration-dependent manner, (v) RDSs elicited Ca efflux from passively loaded cardiac SR vesicles (i.e., with nonfunctional Ca pumps in the absence of Mg-ATP) and stimulated Ca -dependent ATPase activity, which indicated that RDS uncoupled Ca uptake and did not act at the Ca , Mg -ATPase. These results indicate that RDSs selectively oxidize critical sulfhydryl site(s) on or adjacent to a Ca release channel protein channel and thereby trigger Ca release. Conversely, reduction of these sites reverses the effects of RDSs by closing Ca release channels, which results in active Ca reuptake by Ca , Mg -ATPase. These compounds can thus provide a method to covalently label and identify the protein involved in Ca release from cardiac SR. © 1990. 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ a free
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    Digital Object Identifier (doi)

    Author List

  • Prabhu SD; Salama G
  • Start Page

  • 275
  • End Page

  • 283
  • Volume

  • 282
  • Issue

  • 2