Differential localization of protein kinase A type II isozymes in the Golgi-centrosomal area

Selectivity in the action of cAMP may be mediated by compartmentalized pools of cyclic AMP-dependent protein kinase (PKA). PKA type II is directed to different subcellular loci by interaction of the type II regulatory subunits (RIIalpha, RIIbeta) with A-kinase anchoring proteins. In order to separately investigate the subcellular localization of PKA type II isozymes, monospecific antibodies to human RIIalpha and RIIbeta subunits of PKA were developed. We demonstrate that centrosomes bind both RIIalpha and RIIbeta. Centrosomes were the preferred intracellular anchoring site for RIIbeta. However, centrosomal localization of RIIbeta was observed only in some highly differentiated cells such as keratinocytes, granulosa cells, and macrophages and in all neoplastic cell lines examined. Centrosomal localization of RIIbeta was not observed in normal undifferentiated cells such as fibroblasts, myoblasts, and T and B cells. In contrast, RIIalpha was abundant in the Golgi area and in the trans-Golgi network (TGN). Furthermore, although RIIalpha appeared to colocalize with microtubules in the Golgi/TGN, extractions with nonionic detergent demonstrated that RIIalpha was mainly membrane-associated. In addition, alterations of microtubule dynamics with Nocodazole or Taxol affected the distribution of the detergent-extractable pool of RIIalpha, indicating that RIIalpha may localize with microtubule-associated vesicles. Thus, RIIalpha and RIIbeta clearly localize differently in the Golgi-centrosomal region. This indicates specific roles for PKA isozymes containing either RIIalpha or RIIbeta.