Molecular genetic analysis of two G alpha protein subunits in Dictyostelium - PubMed (original) (raw)

. 1991 Jan 15;266(2):1220-8.

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Molecular genetic analysis of two G alpha protein subunits in Dictyostelium

A Kumagai et al. J Biol Chem. 1991.

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Abstract

In Dictyostelium, chemotaxis to folate during growth and cAMP during aggregation is controlled via cell surface receptors. To study the role of two G alpha proteins (G alpha 1 and G alpha 2) in these responses, we examined the physiological and biochemical effects of null mutations caused by antisense mutagenesis and gene disruptions. Disruption of G alpha 2 results in an aggregation-deficient phenotype and a loss of cAMP receptor-mediated functions, including activation of adenylate cyclase, guanylate cyclase, and gene expression and in a loss of GTP-mediated decrease in receptor affinity for cAMP, but it has no effect on chemotaxis to folate or folate activation of guanylate cyclase. These phenotypes can be rescued by a vector expressing G alpha 2, suggesting G alpha 2 is coupled to a cAMP receptor but not to folate receptors. Loss of G alpha 1 expression resulted in no visible growth or developmental phenotype, including cAMP- and folate-stimulated responses, suggesting G alpha 1 function is either not essential under standard laboratory conditions or is encoded by multiple genes. Availability of null mutations provides suitable genetic backgrounds for expressing mutant G alpha protein subunits which can then be used to examine the physiological roles of G alpha 1 and G alpha 2. Construction of these gene disruptions was facilitated by using the auxotrophic marker THY1, which allowed for selection of single-copy insertions into the genome.

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