Loss of PKA-C3 causes behavioral and degenerative phenotypes.

<p><b>A</b>. Inducing a UAS-PKA-C3^RNAi construct pan-neuronally with <i>Appl</i>-GAL4 (<i>Appl</i>>PKA-C3^RNAi) did not result in a significant reduction in performance compared to controls (<i>Appl</i>>lacZ) when only one copy of each construct is used (het.). However, when using two copies of the RNAi construct (hom.), the flies performed significantly worse than controls. All flies were 14 d old females. n = is number of groups (10–15 flies) tested. Analysis was done using one-way ANOVA with a Dunett's post test and the variance was not different. **p<0.01. <b>B</b>. Measuring the vacuole area in 14 d old <i>Appl</i>>dcr;PKA-C3^RNAi flies did not reveal a significant difference to age-matched <i>Appl</i>>dcr controls. However, when aging the PKA-C3 knock-down flies for 30 d they showed significantly increased vacuolization compared to controls. n = number of analyzed flies. Student's t-test were used to compare vacuole size between flies of a given age. The variance was not significantly different when comparing 14 d old flies but were different when comparing 30 d old flies; p<0.001. *p<0.05. <b>C</b>. Model showing the interactions between SWS (light grey) and PKA-C3 (dark grey) and the proposed effects of TOCP. SWS binds to the PKA-C3 subunit via its interaction domain which contains the conserved arginine (R) that is required for binding and that is mutated in SWS^R133A. S indicates the serine to which organophosphates bind. Canonical regulatory PKA subunits form dimers and release the catalytic subunits upon binding of cAMP. Although this has not been confirmed for SWS yet, potential cyclic nucleotide binding sites have been identified in SWS. In our model, binding of TOCP (or its metabolite SCOP) and the following aging reaction causes a conformational change that prevents the release and activation of PKA-C3, possibly by interfering with cyclic nucleotide binding.