cAMP-dependent protein kinase type RI is found in clusters in the rat detergent-insoluble neuronal fraction

Different types of cAMP dependent regulatory subunits have been characteriz ed in the mam malian brain: RI alpha and beta, RII alpha and beta. The subc ellular distribution of RI subunits has been examined in the rat brain. Par tial amino acid sequencing of tryptic fragments from the Triton insoluble p ellet of the rat brain shows that cAMP dependent regulatory subunits type R I alpha are found in this fraction. Immunohistochemistry shows that Triton- insoluble RI subunits are concentrated to form clusters and this distributi on is distinct from RII subunits. Immunohistochemistry and fluorescent cAMP labeling show that the clusters bind fluorescent cAMP analogues. These res ults suggest that the high local concentration of RI subunits can modulate cAMP distribution among different cellular compartments. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.