MITOCHONDRIA ARE EXCITABLE ORGANELLES CAPABLE OF GENERATING AND CONVEYING ELECTRICAL AND CALCIUM SIGNALS

We report Ca2+-induced release of Ca2+ from mitochondria (mCICR) depen dent on transitory opening of the permeability transition pore (PTP) o perating in a low conductance mode. The Ca2+ fluxes taking place durin g mCICR are a direct consequence of the mitochondrial depolarization s pike (mDPS) caused by PTP opening. Both mDPS and mCICR can propagate f rom one mitochondrion to another in vitro, generating traveling depola rization and Ca2+ waves. Mitochondria thus appear to be excitable orga nelles capable of generating and conveying electrical and Ca2+ signals . In living cells, mDPS/mCICR is triggered during IP3-induced Ca2+ mob ilization and results in the amplification of the Ca2+ signals primari ly emitted from the endoplasmic reticulum.