Loss of AKAP150 perturbs distinct neuronal processes in mice

Abstract

A-Kinase Anchoring Proteins (AKAPs) ensure the fidelity of second messenger signaling events by directing protein kinases and phosphatases toward their preferred substrates. AKAP150 brings protein kinase A (PKA), the calcium/calmodulin dependent phosphatase PP2B and protein kinase C (PKC) to postsynaptic membranes where they facilitate the phosphorylation dependent modulation of certain ion channels. Immunofluorescence and electrophysiological recordings were combined with behavioral analyses to assess whether removal of AKAP150 by gene targeting in mice changes the signaling environment to affect excitatory and inhibitory neuronal processes. Mislocalization of PKA in AKAP150 null hippocampal neurons alters the bidirectional modulation of postsynaptic AMPA receptors with concomitant changes in synaptic transmission and memory retention. AKAP150 null mice also exhibit deficits in motor coordination and strength that are consistent with a role for the anchoring protein in the cerebellum. Loss of AKAP150 in sympathetic cervical ganglion (SCG) neurons reduces muscarinic suppression of inhibitory M currents and provides these animals with a measure of resistance to seizures induced by the non-selective muscarinic agonist pilocarpine. These studies argue that distinct AKAP150-enzyme complexes regulate contextdependent neuronal signaling events in vivo.AMPA ͉ behavior ͉ KCNQ ͉ knockout S ophisticated systems have evolved to manage the spatial and temporal organization of signal transduction pathways. AKinase Anchoring Proteins (AKAPs) target various protein kinases and phosphatases to subcellular environments where they control the phosphorylation state of neighboring substrates (1). Movement of enzymes in and out of multiprotein complexes contributes to the temporal regulation of signaling. Hence genetic manipulation of AKAP expression impacts the specificity and magnitude of cellular regulation within the context of the whole organism. This is particularly evident in the central nervous system where the elongated and branched morphology of neurons creates many intracellular compartments where AKAPs synchronize neuronal events (2-4).AKAP79/150 is a family of three orthologs (human AKAP79, murine AKAP150, and bovine AKAP75) each initially defined on the basis of its ability to tether the type II PKA holoenzyme (4, 5). Additional binding partners were subsequently identified including PP2B and PKCs (6, 7). Thus, AKAP79/150 complexes can to respond to intracellular second messengers such as cAMP, calcium and phospholipids (7). Furthermore, the simultaneous anchoring of signal transduction and signal termination enzymes influences both forward and backward steps of a cellular event. For example, AKAP79/150 complexes can influence the phosphorylation and action of transmembrane proteins including G protein coupled receptors and adenylyl cyclases (8, 9). Loss of AKAP79/150 from heart cells contributes to the onset of angiotensin II-induced hypertension (10). Electrophysiological approaches have established a role for AKAP79...

Differential Protein Kinase C-dependent Modulation of Kv7.4 and Kv7.5 Subunits of Vascular Kv7 Channels

“…depletion of plasma membrane phosphatidylinositol 4,5-bisphosphate (36 -40), or elevation of cytosolic [Ca 2ϩ ]) (16,41). Our previous findings, however, strongly support involvement of PKC, a less commonly proposed regulator of M-currents (42,43), in the suppression of endogenous Kv7 currents by physiologically relevant concentrations of AVP. PKC inhibitors calphostin C and Ro-31-8220 prevented AVP-induced constriction of MAs and abolished AVP-induced suppression of Kv7 currents in MASMCs and A7r5 cells, suggesting that AVP acts in a PKC-dependent manner (11,12,27).…”

AKAP220 manages apical actin networks that coordinate aquaporin-2 location and renal water reabsorption

“…Consequently, PKA phosphorylation events that augment AQP2 pore function must proceed through other AKAP-associated pools of this kinase. Likely candidates include AKAP18δ, a PKAanchoring protein that codistributes, but does not interact with, AQP2, and AKAP79/150 that tethers PKA to membrane-proximal regions (48)(49)(50)(51). There is clear precedent for AKAPs that participate in PKA-independent signaling events.…”

A-kinase Anchoring Protein 79/150 Recruits Protein Kinase C to Phosphorylate Roundabout Receptors

“…An attractive feature of this hypothesis is that AKAP79/150 signaling complexes also populate the postsynaptic density, where they provide local control of synaptic strength (31,47). In keeping with this notion, deletion of AKAP150 in mice impairs long term depression due to the loss of PKA, PKC, and PP2B anchoring (22,24,25).…”

“…AKAP79/150 binds directly to certain membrane proteins, such as the L-type calcium channel and the KCNQ2 subunits of the M-channel (22,30,(35)(36)(37)(38). In contrast, NMDA and AMPA receptors interact with AKAP79/150 through a bridging interaction with membrane-associated guanylate kinase (MAGUK) proteins (18,19,39).…”

“…Robo2 is expressed throughout the developing murine hippocampus, a region of the brain that is enriched with AKAP79/ 150 (22,34). Thus, a more pertinent validation of the interaction between these two proteins was to be found in primary cultures of mouse hippocampal neurons grown for 15 DIV.…”