Synergistic Activation of Phospholipase C-β3 by Gαq and Gβγ Describes a Simple Two-State Coincidence Detector
| Autor: | Jimmy Woodson, Ganesh Kadamur, Rosa Gonzalez Silos, Finly Philip, Elliott M. Ross |
|---|---|
| Rok vydání: | 2010 |
| Předmět: |
G protein
Allosteric regulation Phospholipase C beta GTP-Binding Protein beta Subunits Biology Phospholipase Ligands Article General Biochemistry Genetics and Molecular Biology Mice 03 medical and health sciences Enzyme activator 0302 clinical medicine Allosteric Regulation GTP-Binding Protein gamma Subunits Animals Humans 030304 developmental biology 0303 health sciences Agricultural and Biological Sciences(all) Phospholipase C Biochemistry Genetics and Molecular Biology(all) Rats Enzyme Activation Isoenzymes Models Chemical Biochemistry Gq alpha subunit SIGNALING Biophysics biology.protein GTP-Binding Protein alpha Subunits Gq-G11 Signal transduction General Agricultural and Biological Sciences 030217 neurology & neurosurgery |
| Zdroj: | Current Biology. 20:1327-1335 |
| ISSN: | 0960-9822 |
| DOI: | 10.1016/j.cub.2010.06.013 |
| Popis: | Summary Background Receptors that couple to G i and G q often interact synergistically in cells to elicit cytosolic Ca 2+ transients that are several-fold higher than the sum of those driven by each receptor alone. Such synergism is commonly assumed to be complex, requiring regulatory interaction between components, multiple pathways, or multiple states of the target protein. Results We show that cellular G i -G q synergism derives from direct supra-additive stimulation of phospholipase C-β3 (PLC-β3) by G protein subunits Gβγ and Gα q , the relevant components of the G i and G q signaling pathways. No additional pathway or proteins are required. Synergism is quantitatively explained by the classical and simple two-state (inactive↔active) allosteric mechanism. We show generally that synergistic activation of a two-state enzyme reflects enhanced conversion to the active state when both ligands are bound, not merely the enhancement of ligand affinity predicted by positive cooperativity. The two-state mechanism also explains why synergism is unique to PLC-β3 among the four PLC-β isoforms and, in general, why one enzyme may respond synergistically to two activators while another does not. Expression of synergism demands that an enzyme display low basal activity in the absence of ligand and becomes significant only when basal activity is ≤ 0.1% of maximal. Conclusions Synergism can be explained by a simple and general mechanism, and such a mechanism sets parameters for its occurrence. Any two-state enzyme is predicted to respond synergistically to multiple activating ligands if, but only if, its basal activity is strongly suppressed. |
| Databáze: | OpenAIRE |
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