SEXUAL PHEROMONE MODULATES THE FREQUENCY OF CYTOSOLIC CA 2+ BURSTS IN Saccharomyces cerevisiae

TARKOWSKI, NAHUEL; CARBÓ, NATALIA; PEREZ-IPIÑA, EMILIANO; PONCE DAWSON, SILVINA; AGUILAR, PABLO S.

CORDOBA

Congreso; 52th Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2016

SAIB

Transient and highly regulated elevations of cytosolic Ca 2+ control a variety of cellular processes. In budding yeast, Ca 2+ has been implicated in the response to several environmental challenges. Bulk measurements using radioactive Ca 2+ and the luminescent sensor aequorin have shown that in response to pheromone, yeast cells experience a rise of cytosolic Ca 2+ that is mediated by two import systems composed by the Mid1-Cch1- Ecm7 protein complex, and the Fig1 protein. Although this response has been largely studied, there is no report on Ca 2+ dynamics at the single cell level. Here, we adapted protein calcium indicators to yeast and show that both vegetative and pheromone-treated cells exhibit discrete and asynchronous Ca 2+ bursts. Most bursts reach maximal amplitude in 1-10 secs, span between 7 and 30 secs and decay fitting a single exponential model. In vegetative cells bursts are scarce but preferentially occur when cells are transitioning G1 and S phase. Upon pheromone presence Ca 2+ 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, still unidentified, import system. Moreover, we show that the calcineurin-responsive transcription factor Crz1 experiences nuclear localization bursts during the pheromone response.