Adenylate through

The ready reversibility of the kinases and their abundance in cells has the result that all of the free nucleoside phosphates in a cell reflect the relative amounts of the adenosine phosphates in each of the three levels of phosphorylation. Because the adenosine phosphates are primarily involved in energy metabolism, the energy status of the cell is reflected in the relative amounts of ATP, ADP, and adenylate. Through the very facile transphosphorylation reactions, other nucleoside phosphates become similarly distributed among the three levels of phosphorylation perturbations in energy metabolism, such as those caused by substrate deprivation or by anoxia, cause parallel shifts in the relative amounts of the mono-, di-, and triphosphates in all of the nucleotide families. 

Two AR subtypes, Ax and A3, couple through G to inhibit adenylate cyclase, while the other two subtypes, A2a and A2B, stimulate adenylate cyclase through Gs or G0if (for A2a). The A2BAR is also coupled to the activation of PLC through Gq. Furthermore, each of these receptors may couple through the (3,y subunits of the G proteins to other effector systems, including ion channels and phospholipases. Levels of intracellular... 

Kaminski NE, Koh WS, Yang KH, Lee M, Kessler FK. Suppression of the humoral immune response by cannabinoids is partially mediated through inhibition of adenylate cyclase by a pertussis toxin-sensitive G-protein-coupled mechanism. Biochem Pharmacol 1994 48 1899-1908. 

G0 was isolated as an other PTx-ribosylated G-protein which co-purifies with G, but which does not inhibit adenylate cyclase. There are two main isoforms (G0l and Go2), with additional splice-variants. G0 is particularly abundant in the nervous system, comprising up to 1% of membrane proteins. Its main function is to reduce the opening probability of those voltage-gated Ca2+ channels (N- and P/Q-type) involved in neurotransmitter release. Hence, it is largely responsible for the widespread auto-inhibition of transmitter secretion by presynaptic receptors and this effect is mediated through released py subunits. 

Fig. 5 Proposed signal transduction mechanisms that stimulate the pheromone biosynthetic pathway in Helicoverpa zea and Bombyx mori. It is proposed that PBAN binds to a G protein-coupled receptor present in the cell membrane that upon PBAN binding will induce a receptor-activated calcium channel to open causing an influx of extracellular calcium. This calcium binds to calmodulin and in the case of B. mori will directly stimulate a phosphatase that will dephosphorylate and activate a reductase in the biosynthetic pathway. In H. zea the calcium-calmodulin will activate adenylate cyclase to produce cAMP that will then act through kinases and/or phosphatases to stimulate acetyl-CoA carboxylase in the biosynthetic pathway...

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