Selective activation of phospholipase C by recombinant G-protein alpha- and beta gamma-subunits
Receptor activation of phospholipase C (PLC) via G-proteins occurs by pertussis toxin-sensitive and toxin-insensitive signaling pathways. The alpha-subunits of the Gq family are presumed to mediate the toxin-insensitive pathway, but the nature of the G-proteins mediating the toxin-sensitive pathway...
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Veröffentlicht in: | The Journal of biological chemistry 1994-01, Vol.269 (4), p.2814-2819 |
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Zusammenfassung: | Receptor activation of phospholipase C (PLC) via G-proteins occurs by pertussis toxin-sensitive and toxin-insensitive signaling
pathways. The alpha-subunits of the Gq family are presumed to mediate the toxin-insensitive pathway, but the nature of the
G-proteins mediating the toxin-sensitive pathway is not established. Recently, PLC-beta has been shown to be activated by
G-protein beta gamma-subunits of mixed or undefined composition. The relative activities of G-protein subunits that might
activate PLC-beta were examined using defined recombinant alpha- and beta gamma-subunits obtained from the baculovirus expression
system by reconstituting the purified subunits with purified bovine brain PLC-beta 1 or turkey erythrocyte PLC-beta in unilamellar
phospholipid vesicles. Turkey erythrocyte G alpha 11 and recombinant G alpha 11 and G alpha q obtained after expression in
Sf9 cells activated both bovine brain PLC-beta 1 and turkey erythrocyte PLC-beta. In contrast, under the same assay conditions,
recombinant G alpha i1, G alpha i2, G alpha i3, and G alpha o were without effect on either type of PLC. All types of beta
gamma-subunits tested (r beta 1 gamma 2, r beta 1 gamma 3, r beta 2 gamma 2, r beta 2 gamma 3, bovine brain beta gamma or
turkey erythrocyte beta gamma) inhibited G alpha 11-mediated activation of PLC, presumably by promotion of formation of inactive
heterotrimeric G-protein. All types of beta gamma-subunits also markedly stimulated the activity of turkey erythrocyte PLC-beta
but did not activate bovine brain PLC-beta 1. Of the four different beta gamma complexes of defined composition, three stimulated
PLC with similar activities whereas beta 2 gamma 3 was less effective. The data suggest that pertussis toxin-sensitive activation
of PLC is mediated by the beta gamma-subunits of G-proteins acting on specific phospholipase C isoenzymes. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1016/S0021-9258(17)42015-1 |