Shaw potassium channel genes inDrosophila

Abstract

Drosophila Shaw encodes a voltage-insensitive, slowly activating, noninactivating K(+) current. The functional and developmental roles of this channel are unknown. In this study, we use a dominant transgenic strategy to investigate Shaw function and describe a second member of the Shaw family, Shawl. In situ hybridization showed that the two Shaw family genes, Shaw and Shawl, have largely nonoverlapping expression patterns in embryos. Shaw is expressed mainly in excitable cells of the CNS and PNS of late embryos. Shawl is expressed in many nonexcitable cell types: ubiquitously in embryos until the germband extends, then transiently in the developing CNS and PNS, becoming restricted to progressively smaller subsets of the CNS. Ectopic full-length and truncated Shaw localize differently within neurons, and produce uneclosed small pupae and adults with unfurled wings and softened cuticle. This phenotype was mapped to the crustacean cardioactive peptide (CCAP)-neuropeptide circuit. Widespread expression of Shaw in the nervous system results in a reduction in body mass, ether-induced shaking, and lethality. Expression of full-length Shaw had more extreme phenotypic consequences and caused earlier lethality than expression of truncated Shaw in a given GAL4 pattern. Whole cell recordings from ventral ganglion motor neurons expressing the truncated Shaw protein suggest that a major role of Shaw channels in these cells is to contribute to the resting potential.

Functional Dissection of a Neuronal Network Required for Cuticle Tanning and Wing Expansion inDrosophila

“…This observation is consistent with results reported previously by Hodge et al (2005), who found that dominant-negative inhibition of Shaw K ϩ channel function in N CCAP resulted in many animals exhibiting the juvenile phenotype, particularly females. Interestingly, we have observed a similar sexual dimorphism in the effects of NaChBac in N CCAP when using a "weaker" insert that lacks the EGFP tag (data not shown).…”

“…The effects of EKO are consistent with recent observations by Hodge et al (2005), who observed wing expansion deficits in ϳ70% of flies overexpressing the Shaw K ϩ channel in N CCAP . Shaw, which is endogenously expressed in N CCAP , is thought to contribute to the resting leak conductance of cells that express it and should serve to suppress excitability.…”

“…Shaw, which is endogenously expressed in N CCAP , is thought to contribute to the resting leak conductance of cells that express it and should serve to suppress excitability. Interestingly, Hodge et al (2005) found that inhibition of Shaw expression in N CCAP by dominant-negative techniques also resulted in wing expansion deficits in 20 -55% animals, depending on sex. This manipulation suggests that enhancement of excitability in N CCAP may disrupt bursicon release also.…”

“…Within N CCAP , disruption of membrane excitability and synaptic transmission, by constitutive suppression of either Shaw K ϩ channel expression (Hodge et al, 2005) or dynamin function , yields animals with the juvenile phenotype. Similarly, manipulations of the protein kinase A (PKA) pathway also produce juvenile phenotypes, but the cellular locus of action of these manipulations has not been determined (Bantignies et al, 2000;Rodan et al, 2002).…”

Vesicle capture, not delivery, scales up neuropeptide storage in neuroendocrine terminals

“…Panneuronal expression is not convenient for studying type III boutons, however, because of the presence of closely apposed type Ib, Is, and II boutons, which arise from different neurons. Therefore, to generate a basis of comparison with type Ib boutons, Anf-GFP expression was induced specifically in type III boutons with the driver ccap-GAL4 (20), and neuropeptide fluorescence was quantified with wide-field microscopy. These measurements demonstrated sevenfold more neuropeptide in typical spindle-shaped type III boutons than in type Ib boutons ( Fig.…”