title: p53 at the endoplasmic reticulum regulates apoptosis in a Ca2+-dependent manner.
abstract: The tumor suppressor p53 is a key protein in preventing cell transformation and tumor progression. Activated by a variety of stimuli, p53 regulates cell-cycle arrest and apoptosis. Along with its well-documented transcriptional control over cell-death programs within the nucleus, p53 exerts crucial although still poorly understood functions in the cytoplasm, directly modulating the apoptotic response at the mitochondrial level. Calcium (Ca(2+)) transfer between the endoplasmic reticulum (ER) and mitochondria represents a critical signal in the induction of apoptosis. However, the mechanism controlling this flux in response to stress stimuli remains largely unknown. Here we show that, in the cytoplasm, WT p53 localizes at the ER and at specialized contact domains between the ER and mitochondria (mitochondria-associated membranes). We demonstrate that, upon stress stimuli, WT p53 accumulates at these sites and modulates Ca(2+) homeostasis. Mechanistically, upon activation, WT p53 directly binds to the sarco/ER Ca(2+)-ATPase (SERCA) pump at the ER, changing its oxidative state and thus leading to an increased Ca(2+) load, followed by an enhanced transfer to mitochondria. The consequent mitochondrial Ca(2+) overload causes in turn alterations in the morphology of this organelle and induction of apoptosis. Pharmacological inactivation of WT p53 or naturally occurring p53 missense mutants inhibits SERCA pump activity at the ER, leading to a reduction of the Ca(2+) signaling from the ER to mitochondria. These findings define a critical nonnuclear function of p53 in regulating Ca(2+) signal-dependent apoptosis.
authors.affiliation: Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, University of Ferrara, Ferrara 44121, Italy;
authors.forename: Carlotta
authors.initials: C
authors.lastname: Giorgi
authors.affiliation: Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, University of Ferrara, Ferrara 44121, Italy;
authors.forename: Massimo
authors.initials: M
authors.lastname: Bonora
authors.affiliation: Laboratorio Nazionale del Consorzio Interuniversitario per le Biotecnologie (LNCIB), 34012 Trieste, Italy;
authors.forename: Giovanni
authors.initials: G
authors.lastname: Sorrentino
authors.affiliation: Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, University of Ferrara, Ferrara 44121, Italy;
authors.forename: Sonia
authors.initials: S
authors.lastname: Missiroli
authors.affiliation: Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, University of Ferrara, Ferrara 44121, Italy;
authors.forename: Federica
authors.initials: F
authors.lastname: Poletti
authors.affiliation: Department of Biochemistry, Nencki Institute of Experimental Biology, Warsaw 02-093, Poland;
authors.forename: Jan M
authors.initials: JM
authors.lastname: Suski
authors.affiliation: Department of Physics and Astronomy, University of Padua, Padua 35129, Italy; Venetian Institute of Molecular Medicine, Padua 35129, Italy;
authors.forename: Fabian
authors.initials: F
authors.lastname: Galindo Ramirez
authors.affiliation: Department of Biomedical Sciences, University of Padua, Padua 35131, Italy;
authors.forename: Rosario
authors.initials: R
authors.lastname: Rizzuto
authors.affiliation: Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, University of Ferrara, Ferrara 44121, Italy;
authors.forename: Francesco
authors.initials: F
authors.lastname: Di Virgilio
authors.affiliation: Dulbecco Telethon Institute, Istituto di Ricerche Farmacologiche Mario Negri, Milan 20156, Italy;
authors.forename: Ester
authors.initials: E
authors.lastname: Zito
authors.affiliation: Cancer Genetics Program, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215; and Dipartimento di Scienze della Vita, Univeristà degli Studi di Trieste, 34128 Trieste, Italy.
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Pandolfi
authors.affiliation: Department of Biochemistry, Nencki Institute of Experimental Biology, Warsaw 02-093, Poland;
authors.forename: Mariusz R
authors.initials: MR
authors.lastname: Wieckowski
authors.affiliation: Department of Physics and Astronomy, University of Padua, Padua 35129, Italy; Venetian Institute of Molecular Medicine, Padua 35129, Italy;
authors.forename: Fabio
authors.initials: F
authors.lastname: Mammano
authors.affiliation: Laboratorio Nazionale del Consorzio Interuniversitario per le Biotecnologie (LNCIB), 34012 Trieste, Italy; Dipartimento di Scienze della Vita, Univeristà degli Studi di Trieste, 34128 Trieste, Italy.
authors.forename: Giannino
authors.initials: G
authors.lastname: Del Sal
authors.affiliation: Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, University of Ferrara, Ferrara 44121, Italy; pnp@unife.it.
authors.forename: Paolo
authors.initials: P
authors.lastname: Pinton
mesh_terms: D000331:Aequorin / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005434:Flow Cytometry; D031541:Fluorescence Resonance Energy Transfer; D016257:Fura-2; D055785:Gene Knockdown Techniques; D006801:Humans; D047468:Immunoprecipitation; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D016159:Tumor Suppressor Protein p53; D000331:Aequorin; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium; D016257:Fura-2
keywords: apoptosis; calcium; endoplasmic reticulum; mitochondria-associated membranes; p53