PKA-mediated Golgi remodeling during cAMP signal transmission.

Cyclic AMP (cAMP)-dependent protein kinase A (PKA) is part of the set of signaling proteins that are stably associated to the cytosolic surface of Golgi membranes in mammalian cells. In principle, Golgi-associated PKA could participate in either signal transduction events and/or the coordination of Golgi transport activities. Here, we show data indicating that although Golgi-associated PKA is activated fast and efficiently during cell stimulation by an extracellular ligand it does not contribute significantly to cAMP signal transmission to the nucleus. Instead, most of the PKA catalytic subunits Calphaderived from the Golgi complex remain localized in the perinuclear cytoplasm where they induce changes in Golgi structural organization. Thus, in stimulated cells the Golgi complex appears collapsed, showing increased colocalization of previously segregated markers and exhibiting merging of different proximal cisternae within a single stack. In contrast, the trans-Golgi network remains as a separate compartment. Consequently, the rate of protein transport is increased whereas glycan processing is not severely affected. This remodeling process requires the presence of PKA activity associated to the Golgi membranes. Together these data indicate that Golgi-associated PKA activity is involved in the adaptation of Golgi dynamic organization to extracellular signaling events.