title: FADD-calmodulin interaction: a novel player in cell cycle regulation.
abstract: Analyses of knockout and mutant transgenic mice as well as in vitro studies demonstrated a complex role of FADD in the regulation of cell fate. FADD is involved in death receptor induced apoptosis, cell cycle progression and cell proliferation. In a search for mechanisms that might regulate FADD functions, we identified, upon the screening of a lambda-phage cDNA library, calmodulin (CaM) as a novel FADD interacting protein. CaM is a key mediator of signals by the secondary messenger calcium and it is an essential regulator of cell cycle progression and cell survival. Here, we describe the identification and characterization of two calcium dependent CaM binding sites in the alpha helices 8-9 and 10-11 of FADD. Phosphorylation of human FADD at the C-terminal serine 194, by casein kinase I alpha (CKIalpha), has been shown to regulate FADD-dependent non-apoptotic activities. Remarkably, we showed that both FADD and CaM are CKIalpha substrates and that in synchronized HeLa cells, FADD, CaM and CKIalpha co-localize at the mitotic spindle in metaphase and anaphase. Moreover, complementation experiments in Jurkat FADD-/- T cells indicated that: a) cells expressing FADD mutants in the CaM binding sites are protected from Taxol-induced G2/M cell cycle arrest; b) FADD/CaM interaction is not required for Fas receptor-mediated apoptosis although Fas and CaM might compete for binding to FADD. We suggest that the interplay of FADD, CaM and CKIalpha may have an important role in the regulation of cell fate.
authors.affiliation: Istituto di Biologia Cellulare, Consiglio Nazionale delle Ricerche, Campus A. Buzzati-Traverso, Monterotondo, Rome, Italy.
authors.forename: Giuliana
authors.initials: G
authors.lastname: Papoff
authors.forename: Nadia
authors.initials: N
authors.lastname: Trivieri
authors.forename: Roberta
authors.initials: R
authors.lastname: Crielesi
authors.forename: Francesca
authors.initials: F
authors.lastname: Ruberti
authors.forename: Sonia
authors.initials: S
authors.lastname: Marsilio
authors.forename: Giovina
authors.initials: G
authors.lastname: Ruberti
mesh_terms: D000818:Animals; D002147:Calmodulin / Q000235:genetics / Q000378:metabolism*; D048128:Casein Kinase Ialpha / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D053200:Fas-Associated Death Domain Protein / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D009154:Mutation; D017239:Paclitaxel / Q000494:pharmacology; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism; D050257:Tubulin Modulators / Q000494:pharmacology
chemical_list: D002147:Calmodulin; D053200:Fas-Associated Death Domain Protein; D011993:Recombinant Fusion Proteins; D050257:Tubulin Modulators; D048128:Casein Kinase Ialpha; D017239:Paclitaxel