A-kinase anchoring proteins (AKAPs) influence the spatial and temporal regulation of cAMP signaling events. Anchoring of PKA in proximity to certain adenylyl cyclase (AC) isoforms is thought to enhance the phosphorylation dependent termination of cAMP synthesis. Using a combination of immunoprecipitation and enzymological approaches, we show that the plasma membrane targeted anchoring protein AKAP9/Yotiao displays unique specificity for interaction and the regulation of a variety of AC isoforms. Yotiao inhibits AC 2 and 3, but has no effect on AC 1 or 9, serving purely as a scaffold for these latter isoforms. Thus, Yotiao represents an inhibitor of AC2. The N terminus of AC2 (AC2-NT), which binds directly to amino acids 808 -957 of Yotiao, mediates this interaction. Additionally, AC2-NT and Yotiao (808 -957) are able to effectively inhibit the association of AC2 with Yotiao and, thus, reverse the inhibition of AC2 by Yotiao in membranes. Finally, disruption of Yotiao-AC interactions gives rise to a 40% increase in brain AC activity, indicating that this anchoring protein functions to directly regulate cAMP production in the brain. 2). This family of proteins functions to target PKA and other cAMP effector proteins to specific regions of the cell allowing for increased signaling specificity. Several members of this diverse protein family bind other receptors, channels, or enzymes to form tightly regulated signaling modules, facilitating PKA interactions with its downstream effectors. In addition, these signaling modules often constitute feedback loops between kinases and phosphatases or recruit phosphodiesterases to terminate the cAMP signal (3).Our labs previously identified a complex containing AKAP79/ 150 and type 5 adenylyl cyclase (AC), that facilitates the spatiotemporal organization of cAMP signaling (4). AKAP79 inhibits AC5 activity, while providing a mechanism for feedback inhibition via PKA phosphorylation of anchored AC5. However, with Ϸ30 gene families of AKAPs identified thus far, and nine mammalian isoforms of AC, it begs the question, does AKAP scaffolding of AC and PKA represent a general paradigm for cAMP signaling? The AKAP Yotiao represents an ideal test case to begin to address this question. Yotiao is a splice variant of the AKAP9 gene and is present on the plasma membrane (5, 6). In addition to PKA, Yotiao binds protein phosphatase 1 (PP1), NMDA receptors, the heart potassium channel subunit KCNQ1, and the IP 3 R1 (5, 7-9). Interestingly, AKAP anchored PKA phosphorylation of the NMDA receptor, KCNQ1, and IP 3 R1 is necessary for each effector's normal function (8-11). For example, disruption of the KCNQ1 association with Yotiao gives rise to long QT syndrome, a type of heart arrhythmia that can be fatal (12). The requirement for a tight coupling between PKA and KCNQ1, and other effectors suggests that cAMP production must also be tightly regulated, perhaps as even part of this complex.We now show that Yotiao is associated with brain and heart adenylyl cyclases. Yotiao displays specificity am...