Sexual pheromone modulates the frequency of cytosolic Ca2+ bursts in Saccharomyces cerevisiae.
Carbo, N., Tarkowski, N., Ipina, E. P., Dawson, S. P. and Aguilar, P. S.
Laboratorio de Biologia Celular de Membranas, Institut Pasteur de Montevideo, Montevideo 11400, Uruguay.
Laboratorio de Biologia Celular de Membranas, Instituto de Investigaciones Biotecnologicas, Universidad de San Martin, San Martin 1650CPZ, Argentina.
Departamento de Fisica and IFIBA, CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EGA, Argentina.
Laboratorio de Biologia Celular de Membranas, Institut Pasteur de Montevideo, Montevideo 11400, Uruguay paguilar@iib.unsam.edu.ar.
Transient and highly regulated elevations of cytosolic Ca2+ control a variety of cellular processes. Bulk measurements using radioactive Ca2+ and the luminescent sensor aequorin have shown that in response to pheromone, budding yeast cells undergo a rise of cytosolic Ca2+ that is mediated by two import systems composed of the Mid1-Cch1-Ecm7 protein complex and the Fig1 protein. Although this response has been widely studied, there is no treatment of Ca2+ dynamics at the single-cell level. Here, using protein calcium indicators, we show that both vegetative and pheromone-treated yeast cells exhibit discrete and asynchronous Ca2+ bursts. Most bursts reach maximal amplitude in 1-10 s, range between 7 and 30 s, and decay in a way that fits a single-exponential model. In vegetative cells, bursts are scarce but preferentially occur when cells are transitioning G1 and S phases. On pheromone presence, Ca2+ burst occurrence increases dramatically, persisting during cell growth polarization. Pheromone concentration modulates burst frequency in a mechanism that depends on Mid1, Fig1, and a third, unidentified, import system. We also show that the calcineurin-responsive transcription factor Crz1 undergoes nuclear localization bursts during the pheromone response.
Molecular Biology of the Cell 28(4): 501-510 (2017)