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E Carafoli

Publications and source records attributed to E Carafoli.

339 records · Page 19Linked to original sources
PubMed1966

Electron microscope studies on the active accumulation of Sr++ by rat-liver mitochondria.

Electron-opaque granules are deposited in isolated rat-liver mitochondria concomitant with the energy-linked accumulation of Sr(++) by these organelles. High temperature microincineration (600 degrees C) of thin sections of mitochondria containing different amounts of Sr(++) shows that a clear qualitative correlation exists between the number of inorganic residues remaining after incineration and the amount of Sr(++) translocated into the mitochondria. By loading the mitochondria with consecutive pulses of small amounts of Sr(++) ("multiple-pulse" loading), very early stages of granule formation can be detected; the first detectable deposits are seen closely associated with the cristae. The evidence presented supports the hypothesis that mineral deposition following or during the in vitro accumulation of ions by mitochondria occurs, at least initially, at sites on these membranes and not as nonspecific precipitates in the mitochondrial matrix. The large number of electron-opaque deposits (100 to 200) seen in single thin sections of individual mitochondria having accumulated intermediate levels of Sr(++) clearly exceeds the number of normal dense granules in rat-liver mitochondria, indicating that the normal matrix granules per se do not constitute sites essential for deposition. At the highest levels of Sr(++) uptake studied in the multiple-pulse loading experiments, needlelike deposits are seen, a result which suggests that the structural form ("crystallinity") of the mineral deposits may be determined by the rate of accumulation.

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PubMedDate not supplied

Calcium, protease action, and the regulation of the cell cycle.

Proteolysis is a key event in the control of the cell cycle. Most of the proteins which are degraded at specific cycle points, e.g. cyclins A, B, and E, are substrates of the ubiquitin/proteasome pathway. The Ca2+ dependent neutral protease calpain also cleaves cell cycle proteins, among them cyclin D1 and the c-mos proto-oncogene product which is a component of the CSF. The proteasome itself, however, may be under Ca2+ control through the binding of Ca2+ to its 29 kDa regulatory subunit. Calpain undergoes relocation among cell compartments during the various steps of the mitotic and meitotic cycles. It promotes the initiation and the progression of mitosis when injected into the perinuclear space of synchronized PtK1 cells, and the resumption of meiosis when directly injected into the nuclei of prophase-arrested starfish oocytes. Apart from the proteins mentioned above, most of the substrates of calpain which become cleaved during mitosis and meiosis are still unknown. Microtubule-associated proteins are likely candidates.

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