A serpentine receptor-dependent, G beta- and Ca2+ influx-independent pathway regulates mitogen-activated protein kinase ERK2 in Dictyostelium

Ca2+ influx and mitogen-activated protein (MAP) kinase activation are impor tant phenomena in signal transduction, which are often interconnected. We i nvestigated whether serpentine receptor-dependent, G beta-independent activ ation of MAP kinase ERK2 by chemoattractant cyclic AMP (cAMP) is mediated b y Ca2+ influx in the social amoeba Dictyostelium discoideum. We generated a D. discoideum double mutant, which harbours a temperature-sensitive G beta subunit and expresses the apoaequorin protein. Utilizing this mutant, we d emonstrate that cAMP induced Ca2+ influx into intact D. discoideum cells ca n be blocked completely at both the permissive and the restrictive temperat ure, by using either gadolinium ions or Ruthenium Red. Under the same exper imental conditions, these substances do not abolish cAMP stimulation of ERK 2 at either temperature, We conclude that there is a G beta- and Ca2+ influ x-independent pathway for the receptor-dependent activation of MAP kinase E RK2 in D. discoideum. (C) 1999 Academic Press.