A chemoattractant receptor controls development in Dictyostelium discoideum

Area of Science:

• Molecular Biology
• Developmental Biology
• Cell Biology

Background:

• Dictyostelium discoideum expresses cell surface cyclic AMP receptors during early development.
• These receptors are hypothesized to coordinate cell aggregation and regulate gene expression.
• The cyclic AMP receptor's role in development is critical but not fully elucidated.

Purpose of the Study:

• To clone the cyclic AMP receptor cDNA and analyze its expression and function.
• To investigate the necessity of the cyclic AMP receptor for Dictyostelium discoideum development.
• To elucidate the structural and functional characteristics of the cyclic AMP receptor.

Main Methods:

• Cloning of cyclic AMP receptor cDNA using lambda gt-11 libraries and antiserum screening.
• Analysis of cyclic AMP receptor mRNA expression during development.
• In vitro translation assays using in vitro transcribed complementary RNA.
• Expression of cDNA and antisense mRNA in Dictyostelium cells to assess receptor function and developmental phenotype.

Main Results:

• The cyclic AMP receptor mRNA is developmentally regulated, peaking at 3-4 hours.
• Expression of antisense mRNA abolished cyclic AMP receptor protein production and blocked cell aggregation.
• Transformed cells expressing the cDNA exhibited specific cyclic AMP binding.
• The deduced amino acid sequence shows similarity to rhodopsins, suggesting a G protein-coupled receptor structure.

Conclusions:

• The cyclic AMP receptor is essential for Dictyostelium discoideum multicellular development.
• The receptor's structure is conserved among G protein-coupled receptors.
• Ligand-induced phosphorylation at the carboxyl terminus is proposed as a regulatory mechanism.