Seven helix cAMP receptors stimulate Ca2+ entry in the absence of functional G proteins in Dictyostelium

Jacqueline L S Milne, Lijun Wu, Michael Caterina, Peter N Devreotes

Research output: Contribution to journalArticle

Abstract

Surface cAMP receptors (cARs) in Dictyostelium transmit a variety of signals across the plasma membrane. The best characterized cAR, cAR1, couples to the heterotrimeric guanine nucleotide-binding protein (G protein) α-subunit Gα2 to mediate activation of adenylyl and guanylyl cyclases and cell aggregation. cAR1 also elicits other cAMP-dependent responses including receptor phosphorylation, loss of ligand binding (LLB), and Ca2+ influx through a Gα2-independent pathway that may not involve G proteins. Here, we have expressed cAR1 and a related receptor, cAR3, in a gβ- strain (Lilly, P., Wu. L., Welker, D. L., and Devreotes, P. N. (1993) Genes & Dev. 7, 986-995), which lacks G protein activity. Both cell lines failed to aggregate, a process requiring the Gα2 and Gβ-subunits. In contrast, cAR1 phosphorylation in cAR1/gβ- cells showed a time course and cAMP dose dependence indistinguishable from those of cAR1/Gβ+ controls. cAMP-induced LLB was also normal in the cAR1/gβ- cells. Finally, cAR1/gβ- cells and cAB3/gβ- cells showed a Ca2+ response with kinetics, agonist dependence, ion specificity, and sensitivity to depolarization agents that were like those of Gβ+ controls, although they accumulated fewer Ca2+ ions per cAMP receptor than the control strains. Together, these results suggest that the Gβ-subunit is not required for the activation or attenuation of cAR1 phosphorylation, LLB, or Ca2+ influx. It may, however, serve to amplify the Ca2+ response, possibly by modulating other intracellular Ca2+ signal transduction pathways.

Original languageEnglish (US)
Pages (from-to)5926-5931
Number of pages6
JournalJournal of Biological Chemistry
Volume270
Issue number11
StatePublished - Mar 17 1995

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Cyclic AMP Receptors
Phosphorylation
Dictyostelium
GTP-Binding Proteins
Ligands
Chemical activation
Ions
Strain control
Signal transduction
Guanine Nucleotides
Guanylate Cyclase
Depolarization
Protein Subunits
Cell membranes
Adenylyl Cyclases
Cell Aggregation
Carrier Proteins
Agglomeration
Genes
Cells

ASJC Scopus subject areas

  • Biochemistry

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Seven helix cAMP receptors stimulate Ca2+ entry in the absence of functional G proteins in Dictyostelium. / Milne, Jacqueline L S; Wu, Lijun; Caterina, Michael; Devreotes, Peter N.

In: Journal of Biological Chemistry, Vol. 270, No. 11, 17.03.1995, p. 5926-5931.

Research output: Contribution to journalArticle

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