Inducible nuclear translocation of a STAT protein in Dictyostelium prespore cells: implications for morphogenesis and cell-type regulation

Dd-STATa, the Dictyostelium STAT (signal transducer and activator of transc ription) protein, is selectively localised in the nuclei of a small subset of prestalk cells located in the slug tip, Injection of cAMP into the extra cellular spaces in the rear of the slug induces rapid nuclear translocation of a Dd-GFP:STATa fusion protein in prespore cells surrounding the site of injection, This suggests that cAMP signals that emanate from the tip direc t the localised nuclear accumulation of Dd-STATa, It also shows that prespo re cells are competent to respond to cAMP, by Dd-STATa activation, and it i mplies that cAMP signalling is in some way limiting in the rear of the slug , Go-injection of a specific inhibitor of the cAR1 serpentine cAMP receptor almost completely prevents the cAMP-induced nuclear translocation, showing that most or all of the cAMP signal is transduced by cAR1, Dd-GFP:STATa al so rapidly translocates into the nuclei of cells adjoining the front and ba ck cut edges when a slug is bisected. Less severe mechanical disturbances, such as pricking the rear of a slug with an unfilled micropipette, also cau se a more limited nuclear translocation of Dd-GFP:STATa. We propose that th ese signalling events form part of a repair mechanism that is activated whe n the migrating slug suffers mechanical damage.