AKAPS act in a two-step mechanism of memory acquisition

Defining the molecular and neuronal basis of associative memories is based upon behavioral preparations that yield high performance due to selection of salient stimuli, strong reinforcement, and repeated conditioning trials. One of those preparations is the Drosophila aversive olfactory conditioning procedure where animals initiate multiple memory components after experience of a single cycle training procedure. Here, we explored the analysis of acquisition dynamics as a means to define memory components and revealed strong correlations between particular chronologies of shock impact and number experienced during the associative training situation and subsequent performance of conditioned avoidance. Analyzing acquisition dynamics in Drosophila memory mutants revealed that rutabaga (rut)-dependent cAMP signals couple in a divergent fashion for support of different memory components. In case of anesthesia-sensitive memory (ASM) we identified a characteristic two-step mechanism that links rut-AC1 to A-kinase anchoring proteins (AKAP)-sequestered protein kinase A at the level of Kenyon cells, a recognized center of olfactory learning within the fly brain. We propose that integration of rut-derived cAMP signals at level of AKAPs might serve as counting register that accounts for the two-step mechanism of ASM acquisition

The SIB Swiss Institute of Bioinformatics' resources: focus on curated databases

The SIB Swiss Institute of Bioinformatics (www.isb-sib.ch) provides world-class bioinformatics databases, software tools, services and training to the international life science community in academia and industry. These solutions allow life scientists to turn the exponentially growing amount of data into knowledge. Here, we provide an overview of SIB's resources and competence areas, with a strong focus on curated databases and SIB's most popular and widely used resources. In particular, SIB's Bioinformatics resource portal ExPASy features over 150 resources, including UniProtKB/Swiss-Prot, ENZYME, PROSITE, neXtProt, STRING, UniCarbKB, SugarBindDB, SwissRegulon, EPD, arrayMap, Bgee, SWISS-MODEL Repository, OMA, OrthoDB and other databases, which are briefly described in this article

Peptides for disruption of PKA anchoring

Abstract Adaptor or scaffolding proteins are at the basis of multiprotein complexes that spatially and temporally co-ordinate the propagation and integration of a broad range of cellular events. One class of scaffolding proteins are AKAPs (A-kinase-anchoring proteins). They sequester PKA (protein kinase A) and other signalling molecules including phosphodiesterases, other protein kinases and protein phosphatases to specific subcellular compartments. AKAP-dependent protein-protein interactions play a role in many physiologically relevant processes. For example, AKAP-PKA interactions are essential for the vasopressin-mediated water reabsorption in renal collecting duct principal cells or β-adrenoceptor-induced increases in cardiac myocyte contractility. Here, we discuss recently developed peptide disruptors of AKAP-PKA interactions. Such peptides are valuable tools to study the relevance of PKA anchoring in cellular processes. A variety of hormones, neurotransmitters and other stimuli mediate activation of the G s /adenylate cyclase system and thereby induce the generation of the second messenger cAMP and activation of PKA (protein kinase A), a serine/threonine kinase. The inactive PKA holoenzyme consists of two catalytic (C) and dimeric regulatory subunits of type I (RIα or RIβ) or type II (RIIα or RIIβ). Binding of cAMP to the Rsubunits causes a conformational change, resulting in the release and thereby activation of the catalytic subunits. The sequence of events leading to PKA activation may be evoked by different stimuli in the same cell at the same time. Still, each stimulus elicits a specific cellular response. Classical examples are the effects of PGE 1 (prostaglandin E 1 ) and β-adrenoceptor agonists (e.g. isoprenaline) on cardiac myocytes. Isoprenaline acts as an inotropic agent, whereas PGE 1 does not, although both agents activate the G s /adenylate cyclase system. However, isoprenaline induces a rise in cAMP predominantly in the microsomal fraction, whereas PGE 1 increases cytosolic cAMP Compartmentalization involves scaffolding proteins concentrating signalling molecules at specific sites within cells, thereby limiting their access to only a subset of their targets. Prototypic scaffolding proteins are AKAPs (A-kinaseanchoring proteins) In vitro analyses and cellular assays revealed that the peptide Ht31 functions as a non-selective disruptor of AKAP-RI and AKAP-RII interactions. Alto et al. [6] determined the minimal RII-binding domains of ten AKAPs. The amino acid sequences of the peptides with the highest binding affinities (derived from AKAP2, AKAP5, AKAP6, AKAP7 and AKAP13) were further optimized with regard to RII binding by a combination of bioinformatics and substitution analysis of all positions. The resulting final high-affinity peptide was termed AKAP in silico (AKAP IS ). The dissociation constants for the binding of AKAP IS to RIα (K D = 0.23 ± 0.05 µM) and RIIα (K D = 0.45 ± 0.07 nM) subunits were determined by fluorescence polarization. The ability of AKAP IS to disrupt PKA anchoring was, e.g., revealed by its ability to evoke a rapid reduction of GluR1 receptor currents in whole cell patch-clamp experiments The dual specificity AKAPs AKAP1 and AKAP10 (D-AKAP1 and D-AKAP2) bind both RI and RII subunits of PKA. chose the PKA-anchoring domain of AKAP10 as a basis for the generation of the peptide AKB-RI (where AKB is A-kinase-binding) (FEELA-WKIAKMIWSDVFQQ). It binds RIα subunits with approx. 90-fold higher affinity (K D = 5.2 ± 0.5 nM) than RIIα subunits (K D = 456 ± 33 nM) and thus preferentially disrupts AKAP-RI interactions. In addition, the peptide AKB-RII C 2006 Biochemical Societ

Peptides for disruption of PKA anchoring

Adaptor or scaffolding proteins are at the basis of multiprotein complexes that spatially and temporally co-ordinate the propagation and integration of a broad range of cellular events. One class of scaffolding proteins are AKAPs (A-kinase-anchoring proteins). They sequester PKA (protein kinase A) and other signalling molecules including phosphodiesterases, other protein kinases and protein phosphatases to specific subcellular compartments. AKAP-dependent protein-protein interactions play a role in many physiologically relevant processes. For example, AKAP-PKA interactions are essential for the vasopressin-mediated water re-absorption in renal collecting duct principal cells or beta-adrenoceptor-induced increases in cardiac myocyte contractility. Here, we discuss recently developed peptide disruptors of AKAP-PKA interactions. Such peptides are valuable tools to study the relevance of PKA anchoring in cellular processes

Local convergence of the symmetric rank-one iteration

SIGLEAvailable from TIB Hannover: RR 1843(95-07) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

HT31: THE first protein kinase A anchoring protein to integrate protein kinase A and Rho signaling

In an attempt to isolate protein kinase A anchoring proteins (AKAPs) involved in vasopressin-mediated water reabsorbtion, the complete sequence of the human AKAP Ht31 was determined and a partial cDNA of its rat orthologue (Rt31) was cloned. The Ht31 cDNA includes the estrogen receptor cofactor Brx and the RhoA GDP/GTP exchange factor protolymphoid blast crisis (Lbc) sequences. The Ht31 gene was assigned to chromosome 15 (region q24-q25). It encodes Ht31 and the smaller splice variants Brx and proto-Lbc. A protein of the predicted size of Ht31 (309 kDa) was detected in human mammary carcinoma and HeLa cells. Anti-Ht31/Rt31 antibodies immunoprecipitated RhoA from primary cultured rat renal inner medullary collecting duct cells, indicating an interaction between the AKAP and RhoA in vivo. These results suggest that Ht31/ Rt31. represent a new type of AKAP, containing both an anchoring and a catalytic domain, which appears to be capable of modulating the activity of an interacting partner. Ht31/Rt31 have the potential to integrate Rho and protein kinase A signaling pathways, and thus, are prime candidates to regulate vasopressin-mediated water reabsorbtion. (C) 2001 Federation of European Biochemical Societie

Compartmentalization of cAMP-dependent signaling by phosphodiesterase-4D is involved in the regulation of vasopressin-mediated water reabsorption in renal principal cells

The cAMP/protein kinase A (PKA)-dependent insertion of water channel aquaporin-2 (AQP2)-bearing vesicles into the plasma membrane in renal collecting duct principal cells (AQP2 shuttle) constitutes the molecular basis of arginine vasopressin (AVP)-regulated water reabsorption. cAMP/PKA signaling systems are compartmentalized by A kinase anchoring proteins (AKAP) that tether PKA to subcellular sites and by phosphodiesterases (PDE) that terminate PKA signaling through hydrolysis of localized cAMP. In primary cultured principal cells, AVP causes focal activation of PKA. PKA and cAMP-specific phosphodiesterase-4D (PDE4D) are located on AQP2-bearing vesicles. The selective PDE4 inhibitor rolipram increases AKAP-tethered PKA activity on AQP2-bearing vesicles and enhances the AQP2 shuttle and thereby the osmotic water permeability. AKAP18delta, which is located on AQP2-bearing vesicles, directly interacts with PDE4D and PKA. In response to AVP, PDE4D and AQP2 translocate to the plasma membrane. Here PDE4D is activated through PKA phosphorylation and reduces the osmotic water permeability. Taken together, a novel, compartmentalized, and physiologically relevant cAMP-dependent signal transduction module on AQP2-bearing vesicles, comprising anchored PDE4D, AKAP18delta, and PKA, has been identified