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 pool s of cyclic AMP-dependent protein kinase (PKA), PKA type II is directed to different subcellular loci by interaction of the type II regulatory subunit s (RII alpha, RII beta) with A-kinase anchoring proteins. In order to separ ately investigate the subcellular localization of PKA type II isozymes, mon ospecific antibodies to human RII alpha and RII alpha subunits of PHA were developed. We demonstrate that centrosomes bind both RII alpha and RII beta . Centrosomes were the preferred intracellular anchoring site for RII beta. However, centrosomal localization of RII beta was observed only in some hi ghly differentiated cells such as keratinocytes, granulosa cells, and macro phages and in all neoplastic cell lines examined. Centrosomal localization of RII beta was not observed in normal undifferentiated cells such as fibro blasts, myoblasts, and T and B cells. In contrast, RII alpha was abundant i n the Golgi area and in the trans-Golgi network (TGN). Furthermore, althoug h RIIa appeared to colocalize with microtubules in the Golgi/TGN, extractio ns with nonionic detergent demonstrated that RII alpha was mainly membrane- associated. In addition, alterations of microtubule dynamics with Nocodazol e or Taxol affected the distribution of the detergent-extractable pool of R II alpha, indicating that RII alpha may localize with microtubule-associate d vesicles, Thus, RII alpha and RII beta clearly localize differently in th e Golgi-centrosomal region. This indicates specific roles for PKA isozymes containing either RII alpha or RII beta. (C) 1999 Academic Press.