The subunit story thickens

Article Abstract:

Beta subunits of the heterotrimeric G proteins, in assisting signal transduction across cell membranes, help to link specific receptors to a calcium channel. G proteins, called so because they can bind and hydrolyse guanine nucleotides, consist of alpha, beta and gamma subunits. C. Kleuss and colleagues utilized somatostatin and muscarinic cholinergic receptor-mediated inhibition of Ca2+ currents in rat pituitary GH3 cells and nuclear microinjection of antisense oligonucleotides to determine that these subunits have different roles in coupling receptors to the effector system.

Calcium channels, Cellular signal transduction

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Receptor-tyrosine-kinase- and G-beta-gamma-mediated MAP kinase activation by a common signalling pathway

Article Abstract:

Mitogen-activated protein (MAP) kinases can be activated by either G-protein-coupled receptors or tyrosine-kinase receptors, both of which appear to using a common signalling pathways. Shc, Grb2 and Sos become functionally associated through the G-beta-gamma-mediated tyrosine phosphorylation of Shc which occurs before the activation of MAP kinase through Gi-coupled receptors. The blocking of G-beta-gamma-mediated kinase activation by the Shc-Grb2-Sos complex indicates a common pathway of the activation with GPCRs and RTKs.

Phosphorylation, Tyrosine

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Isoprenylation in regulation of signal transduction by G-protein-coupled receptor kinases

Article Abstract:

The isoprenoids, a group of unsaturated lipids, form the molecular basis for the ability of the rhodopsin kinase and beta-adrenergic receptor kinase to begin to deactivate the G-protein-coupled receptors. A 15-C (farnesyl) isoprenoid alters the rhodopsin kinase so that it can commence the deactivation by attaching to photon-activated rhodopsin. Both kinases depend on the isoprenyl moieties to translocate and to be active, showing that the biological regulation of receptors is separate but related.

Rhodopsin

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