The regulation and function of Hu-li tai shao (Hts) at the Drosophila neuromuscular junction

Hu-li tai shao (Hts) is the Drosophila homolog of mammalian adducin, a cytoskeletal protein that regulates the submembranous actin-spectrin network. Potential upstream regulatory proteins that alter the distribution or function of Hts at neuromuscular junctions (NMJ) were evaluated, along with putative interacting proteins and phosphoinositides. Muscle-specific RNAi knockdown of the regulatory PKA subunit or conventional PKC altered immunoreactivity against phosphorylated Hts at the NMJ, suggesting that these kinases are involved in Hts phosphorylation. Hts was required for proper assembly of the spectrin cytoskeleton at the NMJ, as changes in hts expression levels strongly disrupted alpha-Spectrin organization. Hts immunoreactivity colocalized with a GFP reporter for phosphatidylinositol-(4,5)-bisphosphate, which Hts could potentially interact with via its conserved MARCKS-homology domain. The transmembrane engulfment receptor draper genetically interacted with hts. These results highlight many avenues by which Hts may be exerting its influence on NMJ development, and open up worthwhile possibilities for future studies.