Mutations in Drosophila sec15 Reveal a Function in Neuronal Targeting for a Subset of Exocyst Components

Abstract

The exocyst is a complex of proteins originally identified in yeast that has been implicated in polarized secretion. Components of the exocyst have been implicated in neurite outgrowth, cell polarity, and cell viability. We have isolated an exocyst component, sec15, in a screen for genes required for synaptic specificity. Loss of sec15 causes a targeting defect of photoreceptors that coincides with mislocalization of specific cell adhesion and signaling molecules. Additionally, sec15 mutant neurons fail to localize other exocyst members like Sec5 and Sec8, but not Sec6, to neuronal terminals. However, loss of sec15 does not cause cell lethality in contrast to loss of sec5 or sec6. Our data suggest a role of Sec15 in an exocyst-like subcomplex for the targeting and subcellular distribution of specific proteins. The data also show that functions of other exocyst components persist in the absence of sec15, suggesting that different exocyst components have separable functions.

DrosophilaAcyl-CoA Synthetase Long-Chain Family Member 4 Regulates Axonal Transport of Synaptic Vesicles and Is Required for Synaptic Development and Transmission

“…However, alterations in the expressions of mammalian ␤-catenin and scribble, which are required for clustering SVs at presynaptic sites, result in no axonal SV aggregates (Bamji et al, 2003;Sun et al, 2009). Similarly, mutations in Drosophila exocyst components Sec5 and Sec15 involved in the secretory pathway lead to no axonal accumulations either (Murthy et al, 2003;Mehta et al, 2005). Therefore, it is unlikely that the axonal aggregates in dAcsl mutants result from a defect in SV targeting or fusion.…”

The polarity-establishment component Bem1p interacts with the exocyst complex through the Sec15p subunit

“…Recently, a sec15 mutant was identified in a screen for genes required for synaptic specificity in Drosophila (Mehta et al, 2005). The targeting defect evident in the neurons of this mutant suggests that the role of Sec15 in specifying certain areas of the cell cortex for membrane expansion may be conserved through evolution.…”

A Drosophila genetic screen yields allelic series of core microRNA biogenesis factors and reveals post-developmental roles for microRNAs

“…6B; Chotard et al 2005;Mehta et al 2005). Whole eye clones of pasha[6B3] showed no substantial difference in the amplitude of depolarization compared with control eyes, indicating that this mutation does not affect the photoreceptor response to stimulation.…”