The Galpha4 G protein subunit interacts with the MAP kinase ERK2 using a D-motif that regulates developmental morphogenesis in Dictyostelium.
G protein Galpha subunits contribute to the specificity of different signal transduction pathways in Dictyostelium discoideum but Galpha subunit-effector interactions have not been previously identified. The requirement of the Dictyostelium Galpha4 subunit for MAP kinase (MAPK) activation and the identification of a putative MAPK docking site (D-motif) in this subunit suggested a possible interaction between the Galpha4 subunit and MAPKs. In vivo association of the Galpha4 subunit and ERK2 was demonstrated by pull-down and co-immunoprecipitation assays. Alteration of the D-motif reduced Galpha4 subunit-ERK2 interactions but only slightly altered MAPK activation in response to folate. Expression of the Galpha4 subunit with the altered D-motif in galpha4(-)cells allowed for slug formation but not the morphogenesis associated with culmination. Expression of this mutant Galpha4 subunit was sufficient to rescue chemotactic movement to folate. Alteration of the D-motif also reduced the aggregation defect associated with constitutively active Galpha4 subunits. These results suggest Galpha4 subunit-MAPK interactions are necessary for developmental morphogenesis but not for chemotaxis to folate.
Nguyen
Hoai-Nghia
HN
Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, 74078-3020, USA.
Hadwiger
Jeffrey A
JA
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002633:Chemotaxis; D017931:DNA Primers; D004023:Dictyostelium / Q000254:growth & development* / Q000502:physiology; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D047468:Immunoprecipitation; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D008969:Molecular Sequence Data; D009024:Morphogenesis; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D019950:Mitogen-Activated Protein Kinase 1; D019204:GTP-Binding Proteins