Nuclear import of PKA subunits requires beta importin-dependent pathway

BACCARINI LETICIA; MORENO, SILVIA; PORTELA PAULA

Mendoza

Congreso; XLVIII reunion Anual de SAIB; 2012

Sociedad Argentina de Investigacion en Bioquimica y Biologia Molecular

In PKA subunits exhibit nuclearcytoplasmic 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 H O . However, the mechanism by which PKAsubunit 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 H O 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 ß-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 ?strain. Thus, nuclear accumulation of each PKA subunit by different ß-karyopherin-dependent pathway could control kinase activity in both compartments.