Developmental morphology and chemotactic responses are dependent on G alpha subunit specificity in Dictyostelium.
Dictyostelium discoideum expresses multiple G alpha subunits but only a single G beta and G gamma subunit suggesting that the specific response to an external signal depends largely on G alpha subunit function or G protein-independent signaling from the receptor. To test the contribution of G alpha subunit functional specificity, the chimeric G alpha subunits, G alpha2/4 and G alpha5/4, were created and analyzed along with wild-type subunits for the ability to substitute for the G alpha4 subunit in mediating responses from folate receptors. The G alpha2/4 subunit, but not the G alpha2 or G alpha5/4 subunits, partly rescued chemotaxis and cGMP accumulation in folate-stimulated g alpha4(-) cells. Expression of the G alpha5/4 or G alpha5 subunits resulted in an inhibition of g alpha4- and wild-type cell movement and a reduced aggregate size in developing wild-type and g alpha5- cells suggesting these subunits mediate similar responses. Only the G alpha4 subunit was capable of correcting developmental morphology in g alpha4- multicellular aggregates suggesting that the chimeric G alpha2/4 or G alpha5/4 subunits were insufficient to provide the G alpha4 function necessary for proper development. These results indicate that Dictyostelium G alpha subunit specificity is not limited to receptor coupling and that G alpha subunit sequences outside of the carboxyl terminus are important for cell movement and developmental processes.
Hadwiger
Jeffrey A
JA
Department of Microbiology and Molecular Genetics, Oklahoma State University, 307 Life Sciences East, Stillwater, Oklahoma 74078-3020, USA. jeff.hadwiger@okstate.edu
D000595:Amino Acid Sequence; D000818:Animals; D002633:Chemotaxis / Q000187:drug effects; D006152:Cyclic GMP / Q000378:metabolism; D004023:Dictyostelium / Q000166:cytology* / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D005492:Folic Acid / Q000494:pharmacology; D044385:GTP-Binding Protein alpha Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D008969:Molecular Sequence Data; D010641:Phenotype; D021122:Protein Subunits / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism
D044385:GTP-Binding Protein alpha Subunits; D021122:Protein Subunits; D011994:Recombinant Proteins; D005492:Folic Acid; D006152:Cyclic GMP