Nuclear import of PKA subunits requires beta importin-dependent pathway

LETICIA BACCARINI; SILVIA MORENO; PAULA PORTELA

Mendoza, Argentina

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.; 2012

SAIB

In Saccharomyces cerevisiae PKA subunits exhibit nuclear‐cytoplasmic localization regulated by carbon source and growth stage. PKA contains three catalytic subunits, TPK1, TPK2 and TPK3 and one regulatory subunit Bcy1. Previously, we have shown that Tpk1 and Tpk2 can differentially regulate transcriptional activity in response to several stress conditions, such as NaCl and H2O2. However, the mechanism by which PKA subunit enters the nucleus and whether its localization is regulated by osmotic and oxidative stress remains unknown. Here we assessed GFP‐tagged PKA subunits localization in response to NaCl or H2O2 of exponentially glucose cells. Tpk1 showed nuclear accumulation upon stress whereas Tpk2, Tpk3 and Bcy1 localization remained unchanged. PKA subunits showed an ATP‐dependent nuclear accumulation suggesting an active transport mechanism. Using strains in which each of β‐karyopherins was defective at a time we determined that Bcy1 is a KAP95 cargo for glucose growing cells. Tpk1 nuclear import required KAP114/KAP123 both pre‐ and post‐ stress stimulus. Tpk2 required KAP108 for its nuclear import in exponentially glucose growing cells but still shows nuclear import in response to stress in kap108Δ strain. Thus, nuclear accumulation of each PKA subunit by different β‐karyopherin‐dependent pathway could control kinase activity in both compartments.