Cyclase

About: Cyclase is a research topic. Over the lifetime, 10162 publications have been published within this topic receiving 388566 citations.

Adenylate cyclase assembled in vitro: cholera toxin substrates determine different patterns of regulation by isoproterenol and guanosine 5'-triphosphate.

Abstract: Genetic and biochemical evidence indicates that hormone-sensitive adenylate cyclase consists of at least three separable components: hormone receptor (R), a catalytic unit (C) that synthesizes cAMP from ATP, and one or more regulatory factors, which we have termed N, that are required for functional coupling of R and C and also for cyclase stimulation by guanyl nucleotides, NaF, and cholera toxin. The functional absence of N in a S49 lymphoma variant clone, cyc-, allows in vitro assembly of hormone-sensitive adenylate cyclase, using cyc- membranes and N components in detergent extracts from membranes of other cells (Ross, E. M. and Gilman, A. G. Proc. Nat. Acad. Sci., USA 74,3715-3719, 1977). Such cyclase systems, assembled in vitro using N components from wild type S49 cells and turkey erythrocytes, are functionally distinguishable, each resembling—in responses to guanyl nucleotides and isoproterenol—the cyclase system from which the N component was derived. Thus, the N component determines certain functional characteristics of the response to guanine nucleotides and isoproterenol. Human erythrocyte membranes, which are virtually devoid of catalytic adenylate cyclase, also contain the functional N component. Donor extracts of human and turkey erythrocytes and S49 cells contain cholera toxin substrates, by two criteria: 1. The extracts transmit effects of toxin on donor membranes to adenylate cyclase assembled in vitro using cyc- membranes; 2. Incubation with toxin plus [32P]NAD+ specifically radiolabels substrates in each type of membrane, including a peptide of Mr = 42,000, common to all three. The results are consistent with the hypothesis that this peptide participates directly in multiple functions of N.

Compartmentalization of adenylate cyclase and cAMP signalling.

Abstract: Concepts of cAMP signalling have changed dramatically from the linear cascades of just a few years ago, with the realization that numerous cellular processes affect this motif. These influences include other signalling pathways – most significantly Ca2+, scaffolding proteins (which are themselves variously regulated) to organize the elements of the pathway, and subcellular targeting of components. An obvious implication of this organization is that global measurements of cAMP may trivialize the complexity of the cAMP signals and obscure the regulation of targets. In this presentation, current developments on the targeting and assembly of ACs (adenylate cyclases) and their delivery to selected raft or non-raft domains of the plasma membrane will be discussed, along with the susceptibility of raft-targeted ACs to very discrete modes of increases in the intracellular Ca2+ concentration. Single-cell explorations of cAMP dynamics, as measured with cyclic nucleotide-gated channels, are also described in this paper, particularly as applied to cells in which the composition of AKAP (A-kinase anchoring protein)–PKA (protein kinase A)–PDE (phosphodiesterase) assemblies is probed by RNA interference ablation of defined AKAPs. Abbreviations: AC, adenylate cyclase; AKAP, A-kinase anchoring protein; CCE, capacitative Ca2+ entry; CNG channel, cyclic nucleotide-gated channel; FRET, fluorescence resonance energy transfer; GPCR, G-protein-coupled receptor; HEK-293, cell, human embryonic kidney 293 cell; NHE, Na+/H+ exchanger; PDE, phosphodiesterase; PKA, protein kinase A; TM, transmembrane; TMD, TM domain