The Drosophila memory mutant rutabaga (rut) has been previously shown to have a defective subpopu-lation (or functional state) of the enzyme adenylate cyclase. We report here that the reduced adenylate cyclase activity is also associated with a defective responsiveness of the enzyme to forskolin. Forskolin activation isotherms of the enzyme in normal membranes reveal low- and high-affinity forskolin-interacting components; the residual enzyme in the mutant shows a smaller proportion of the high-affinity response. In addition, in mutant membrane preparations, forskolin fails to shift the Km of the enzyme for free Mg2+ and for MgATP, in contrast to the situation in the normal tissue. The defect in the responsiveness to forskolin in rut is even more pronounced in a Lubrol-solubilized enzyme preparation, and is due to intrinsic properties of the cyclase system rather than to the absence (or presence) of a soluble, or detergent solubilized, factor in rut. The reduced forskolin responsiveness maps to the X chromosomal segment 12F5-6 to 13A1-5, within the region previously reported to span the locus that controls both the abortive memory and the lack of Ca2 +-stimulation of adenylate cyclase in rut17. The possible relevance of the findings to postulated molecular mechanisms of short-term memory formation is discussed.
Bibliographical noteFunding Information:
We are grateful to Shoshi Hatsvi for her expert technical assistance. This work was supported by grants from the Fund for Basic Research, The Israel Academy of Science, Jerusalem, and from the Forscheimer Centre for Molecular Genetics (to Y.D.). D.S. is a recipient of a fellowship from the Centre for the Absorption of Scientists, Jerusalem.
- Adenylate cyclase
- Drosophila melanogaster
- Memory mutation
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience