To test whether the positive charges in the Syntaxin1A juxtamembrane domain are also needed for clustering of the protein at synapses in vivo, we used recombination in yeast to generate hemagglutinin (HA)-tagged fruit fly Syntaxin1AKARRAA or HA-tagged wild-type Syntaxin1A. The genomic constructs were inserted using Phi-C-31 integrase at the identical genomic location (25C6) and the proteins are expressed under endogenous fruit fly promotor control. We then assessed the localization of these proteins in relation to the active zone marker RBP. Compared to wild-type HA-Syntaxin1A,

the mutant HA-Syntaxin1AKARRAA overlaps much less with the active zone marker RBP and the mutant protein appears selleck kinase inhibitor more dispersed (Figures 3G–3I). The data are consistent with a model in which Syntaxin1A concentrates with PI(3,4,5)P3 in membranes based on electrostatic interactions between negatively charged PI(3,4,5)P3 head groups and positively charged juxtamembrane residues, resulting in the formation of circular domains in which boundary energy is minimized (Christian et al., 2009). While such a mechanism has previously been proposed for PI(4,5)P2-Syntaxin1A-mediated interactions (Aoyagi et al.,

2005; Lam et al., 2008; McLaughlin and Murray, 2005; van den over Bogaart et al., Ruxolitinib clinical trial 2011), taken together, our in vivo and in vitro data suggest a critically important role for the more negatively charged PI(3,4,5)P3 in Syntaxin1A clustering at synapses. Numerous mutations that affect synaptic transmission result in adult temperature-sensitive paralysis in fruit flies, including dap160, shibire (dynamin), syntaxin1A, CSP, and comatose (NSF) ( Koh et al., 2004; Littleton et al., 1998; Zinsmaier et al., 1994). To test whether reduced PI(3,4,5)P3 availability in the nervous system results

in temperature-dependent paralysis, we placed flies that express PH-GRP1 under control of the neuronal nSybGal4 driver in an empty vial in a water bath at different temperatures and counted the number of flies standing after 3 min. In contrast to controls, PH-GRP1-expressing flies show a dose-dependent temperature sensitivity and at 38°C all flies are paralyzed within 3 min ( Figures 4A and 4B). When flies are placed back at room temperature, they recover slowly (data not shown). This effect is specific to reduced availability of PI(3,4,5)P3, as expressing the PH-GRP1 probe together with the Lyn11-FRB/FKBP-p85 and growing the animals on rapamycin completely rescues temperature-sensitive paralysis and animals behave like controls in this assay ( Figure 4C).