Reactive disulfides trigger Ca2+ release from sarcoplasmic reticulum via an oxidation reaction

Area of Science:

• Biochemistry
• Cell Biology
• Physiology

Background:

• Sarcoplasmic reticulum (SR) Ca2+ release is crucial for muscle contraction.
• Reactive disulfide compounds (RDSs) are known to interact with thiol groups.

Purpose of the Study:

• To investigate the mechanism by which RDSs trigger Ca2+ release from SR vesicles.
• To determine if RDSs target Ca2+ release channels or the Ca2+-ATPase pump.

Main Methods:

• Utilized various RDSs (2,2'-DTDP, 4,4'-dithiodipyridine, SPDP) to induce Ca2+ release from SR vesicles.
• Measured [3H]ryanodine binding to assess interaction with the Ca2+ release channel.
• Investigated the effect of RDSs on Ca2+ uptake and ATPase activity.
• Examined the influence of magnesium and adenine nucleotides on RDS-induced Ca2+ release.
• Observed effects in skinned muscle fibers.

Main Results:

• RDSs specifically oxidize accessible SH sites on SR proteins, leading to increased Ca2+ permeability.
• RDSs act on Ca2+ release channels, not the Ca2+-ATPase, as evidenced by unaffected Ca2+ uptake and ATPase activity.
• RDSs displaced [3H]ryanodine binding, indicating interaction with the ryanodine receptor complex.
• Adenine nucleotides modulated the oxidation of SH groups and subsequent Ca2+ efflux.
• 2,2'-DTDP induced rapid twitches in skinned fibers, blocked by ruthenium red.

Conclusions:

• RDSs trigger Ca2+ release from SR by oxidizing critical SH groups on Ca2+ release channels.
• This oxidation leads to increased SR Ca2+ permeability.
• RDSs provide a valuable tool for covalently labeling proteins involved in regulating SR Ca2+ permeability.