A Serpentine Receptor-Dependent, G- and Ca2+ Influx-Independent Pathway Regulates Mitogen-Activated Protein Kinase ERK2 in Dictyostelium

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A Serpentine Receptor-Dependent, G- and Ca²⁺ Influx-Independent Pathway Regulates Mitogen-Activated Protein Kinase ERK2 in Dictyostelium

Paul W. Schenk, Thomas Nebl, Paul R. Fisher, B. Ewa Snaar-Jagalska

Ca²⁺ influx and mitogen-activated protein (MAP) kinase activation are important phenomena in signal transduction, which are often interconnected. We investigated whether serpentine receptor-dependent, G-independent activation of MAP kinase ERK2 by chemoattractant cyclic AMP (cAMP) is mediated by Ca²⁺ influx in the social amoeba Dictyostelium discoideum. We generated a D. discoideum double mutant, which harbours a temperature-sensitive G subunit and expresses the apoaequorin protein. Utilizing this mutant, we demonstrate that cAMP induced Ca²⁺ influx into intact D. discoideum cells can be blocked completely at both the permissive and the restrictive temperature, by using either gadolinium ions or Ruthenium Red. Under the same experimental conditions, these substances do not abolish cAMP stimulation of ERK2 at either temperature. We conclude that there is a G- and Ca²⁺ influx-independent pathway for the receptor-dependent activation of MAP kinase ERK2 in D. discoideum. Copyright 1999 Academic Press.