The G Protein β Subunit Is Essential for Multiple Responses to Chemoattractants in Dictyostelium

• Published in: The Journal of cell biology 1995-06, Vol.129 (6), p.1667-1675
• Main Authors: Wu, Lijun, Valkema, Romi, Peter J. M. Van Haastert, Devreotes, Peter N.
• Format: Article
• Language: English
• Subjects: Adenylyl Cyclases - metabolism; Animals; B lymphocytes; Biochemistry; Cell growth; Cell lines; Cell Movement; Cell physiology; Cells; Cellular biology; Chemotactic factors; Chemotactic Factors - pharmacology; Chemotaxis; Cyclic AMP - metabolism; Cyclic AMP - pharmacology; Cyclic AMP receptors; Dictyostelium; Dictyostelium - drug effects; Dictyostelium - genetics; Dictyostelium - physiology; GTP-Binding Proteins - genetics; GTP-Binding Proteins - metabolism; Guanosine 5'-O-(3-Thiotriphosphate) - pharmacology; Guanosine Triphosphate - metabolism; Guanylate Cyclase - metabolism; Kinetics; Macromolecular Substances; Mutagenesis; Phagocytosis; Receptors; Signal Transduction; Somatic cells; Time Factors
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.129.6.1667

Increasing evidence suggests that the βγ-subunit dimers of heterotrimeric G proteins play a pivotal role in transducing extracellular signals. The recent construction of Gβ null mutants (gβ -) in Dictyostelium provides a unique opportunity to study the role of βγ dimers in signaling processes mediated by chemoattractant receptors. We have shown previously that gβ - cells fail to aggregate; in this study, we report the detailed characterization of these cells. The gβ - cells display normal motility but do not move towards chemoattractants. The typical GTP-regulated high affinity chemoattractant-binding sites are lost in gβ - cells and membranes. The gβ - cells do not display chemoattractant-stimulated adenylyl cyclase or guanylyl cyclase activity. These results show that in vivo Gβ links chemoattractant receptors to effectors and is therefore essential in many chemoattractant-mediated processes. In addition, we find that Gβ is required for GTPγS stimulation of adenylyl cyclase activity, suggesting that the βγ-dimer activates the enzyme directly. Interestingly, the gβ - cells grow at the same rate as wild-type cells in axenic medium but grow more slowly on bacterial lawns and, therefore, may be defective in phagocytosis.