title: Activation of intracellular calcium by multiple Wnt ligands and translocation of β-catenin into the nucleus: a convergent model of Wnt/Ca2+ and Wnt/β-catenin pathways.
abstract: Ca(2+) and β-catenin, a 92-kDa negatively charged transcription factor, transduce Wnt signaling via the non-canonical, Wnt/Ca(2+) and canonical, Wnt/β-catenin pathways independently. The nuclear envelope is a barrier to large protein entry, and this process is regulated by intracellular calcium [Ca(2+)]i and trans-nuclear potential. How β-catenin traverses the nuclear envelope is not well known. We hypothesized that Wnt/Ca(2+) and Wnt/β-catenin pathways act in a coordinated manner and that [Ca(2+)]i release facilitates β-catenin entry into the nucleus in mammalian cells. In a live assay using calcium dyes in PC3 prostate cancer cells, six Wnt peptides (3A, 4, 5A, 7A, 9B, and 10B) mobilized [Ca(2+)]i but Wnt11 did not. Based upon dwell time (range = 15-30 s) of the calcium waveform, these Wnts could be classified into three classes: short, 3A and 5A; long, 7A and 10B; and very long, 4 and 9B. Wnt-activated [Ca(2+)]i release was followed by an increase in intranuclear calcium and the depolarization of both the cell and nuclear membranes, determined by using FM4-64. In cells treated with Wnts 5A, 9B, and 10B, paradigm substrates for each Wnt class, increased [Ca(2+)]i was followed by β-catenin translocation into the nucleus in PC3, MCF7, and 253J, prostate, breast, and bladder cancer cell lines; both the increase in Wnt 5A, 9B, and 10B induced [Ca(2+)]i release and β-catenin translocation are suppressed by thapsigargin in PC3 cell line. We propose a convergent model of Wnt signaling network where Ca(2+) and β-catenin pathways may act in a coordinated, interdependent, rather than independent, manner.
authors.affiliation: From the Research Department of Cell and Developmental Biology, The Centre for Cell and Molecular Dynamics, Rockefeller Building, University Street, University College London, London WC1E 6JJ, United Kingdom.
authors.forename: Christopher
authors.initials: C
authors.lastname: Thrasivoulou
authors.forename: Michael
authors.initials: M
authors.lastname: Millar
authors.forename: Aamir
authors.initials: A
authors.lastname: Ahmed
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism*; D002522:Chlorocebus aethiops; D055724:Electrophysiological Phenomena; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism*; D008024:Ligands; D008564:Membrane Potentials; D008954:Models, Biological; D009685:Nuclear Envelope / Q000378:metabolism; D015398:Signal Transduction; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D008024:Ligands; D051153:Wnt Proteins; D051176:beta Catenin; D002118:Calcium
keywords: Beta-Catenin; Calcium Signaling; Canonical and Non-canonical Signaling; Cell Signaling; Intranuclear Calcium; Macromolecular Transport; Nuclear Membrane; Nuclear Membrane Potential; Wnt Signaling