Regulatory subunit of the cAMP-dependent protein kinases involved in cAMP signaling in cells (PubMed:10781603, PubMed:9196067). Mediates membrane association by binding to anchoring proteins, such as Akap200 (PubMed:9196067, PubMed:12223401). Might play an essential role in the regulation of neuronal activity in the brain (PubMed:10781603, PubMed:9196067). Tetramer, composed of 2 regulatory (R) and 2 catalytic (C) subunits (PubMed:9196067). In the presence of cAMP it dissociates into 2 active monomeric C subunits and an R dimer (By similarity). Interacts with Akap200 (PubMed:10480936). Localization to the membrane depends on Akap200. Detected in follicle cells, germline-derived cells, germline line stem cells and outer rim of ring canals of nurse cells throughout oogenesis (at protein level). The pseudophosphorylation site binds to the substrate-binding region of the catalytic chain but is not phosphorylated. The physiological significance of phosphorylations by other kinases is unclear (By similarity). RNAi-mediated knockdown increases ethanol sedation sensitivity when first exposed to ethanol and decreases ethanol tolerance following repeated ethanol exposure. Belongs to the cAMP-dependent kinase regulatory chain family.