The membrane protein, stomatin, was first discovered in human erythrocytes and derives its name from the observation that stomatin protein levels are reduced in patients suffering from the hereditary cation transport disease, stomatocytosis. Stomatin Like Proteins (SLPs) in C. elegans include UNC-1 and MEC-2, both of which are expressed in neurons where they localize to the cytoplasmic membrane. Recent work from the Chalfie lab has shown that MEC-2 is required for DEG/ENaC cation transport function in touch cell mechanosensory receptors. In addition, genetic experiments have detected interactions between UNC-1 and UNC-8, a DEG/ENaC protein expressed in ventral cord motor neurons.
unc-24 encodes a novel SLP that includes a C-terminal domain resembling the non-specific Lipid Transfer Protein (nsLTP) in addition to an N-terminal stomatin-like sequence. Interestingly, hSLP-1, the human homologue of UNC-24 is expressed primarily in the brain including the basal ganglia which regulates vertebrate locomotion. Although the function of UNC-24 is unknown, recent work has shown that UNC-24 is required for the cell surface localization and stability of UNC-1. In
unc-24 mutants, UNC-1 protein levels are substantially reduced and largely restricted to perinuclear dots in the vicinity of the Golgi apparatus (Sedensky et al., 2001). Our studies have now shown that a transgene encoding GFP-tagged UNC-24 protein under the control of the
unc-24 promoter is widely expressed in C. elegans neurons and is sufficient to rescue the Unc-24 forward movement defect. UNC-24::GFP protein is primarily localized to bright juxtanuclear puncta; however, weaker yet detectable localization to neuronal processes is evident in some cells (e.g. touch neurons). These results suggest that UNC-24 primarily resides in the Golgi compartment where it may be involved in the processing or sorting of UNC-1. We have prepared an affinity-purified UNC-24 polyclonal antibody to establish the subcellular localization of native UNC-24.