ACTIVATION OF MAP KINASE BY THE LHRH RECEPTOR THROUGH A DUAL MECHANISM INVOLVING PROTEIN-KINASE-C AND A PERTUSSIS-TOXIN-SENSITIVE G-PROTEIN

The LHRH receptor in alpha T3-1 gonadotrope cells was shown to bring about a marked and sustained activation of MAP kinase. This response was prevented by protein kinase C inhibition or down-regulation and could be partially mimicked by phorbol ester. Additional evidence for inhibition of this response by pertussis toxin and partial mimicry by mastoparan (in a pertussis toxin-sensitive manner) provides the first evidence for G(i)/G(o)-mediated signal transduction by the LHRH receptor. This dual mechanism of MAP kinase activation appears to be exceptional amongst the G protein-linked receptors that have been investigated.