Expression and function of variants of slob, slowpoke channel binding protein, in Drosophila.

Slob binds to and modulates the Drosophila Slowpoke (dSlo) calcium-activated potassium channel and also recruits the ubiquitous signaling protein 14-3-3 to the channel regulatory complex. RT-PCR reveals the presence of multiple slob transcripts in Drosophila heads. The transcripts are predicted to encode proteins that we call Slob51 (kDa), Slob57, Slob65, and Slob71. Slob51 and Slob65 are splice variants that lack a motif important for the binding of 14-3-3. Previous microarray analyses demonstrated the circadian cycling of slob mRNA, and we show by quantitative PCR that more than one transcript cycles in fly heads. Using in situ hybridization, we observe differences in the expression patterns of the different transcripts. Immunohistochemistry on Drosophila heads reveals Slob71/65 protein to be enriched in the lateral neurons, in contrast to Slob57/51 protein, which is expressed most prominently in the pars intercerebralis neurons and dorsal giant interneurons. Using a heterologous expression system, we show that different Slobs bind to different extents to dSlo and 14-3-3. These data reveal an unexpected diversity of the dSlo/Slob/14-3-3 dynamic regulatory complex.