Transgenic animals expressing green fluorescent protein (GFP) under the control of a fully rescuing
sphk-1 promoter fragment displayed fluorescence in multiple tissues, including the hypodermis (skin), muscles, the intestine, excretory canal cells, and some neurons in the head and tail.In DA/DB class cholinergic motor neurons, functional GFP-tagged SPHK-1 fusion proteins (SPHK-1-GFP) were detected in extranuclear regions in cell bodies, likely corresponding to Golgi (Sumakovic et al., 2009), occasionally in puncta in dendrites (data not shown), and in puncta at en passant presynaptic terminals (Chan et al., 2012). Colocalization studies revealed that SPHK-1-GFP was closely apposed to but not colocalized with the synaptic vesicle (SV) and actin-associated protein SNN-1/synapsin. In body wall muscles, SPHK-1-GFP was primarily observed on the outer surface of mitochondria as demonstrated by its colocalization with an RFP-tagged outer membrane mitochondrial marker. Thus, SPHK-1 appears to localize to different cellular membranes depending on cell type.SPHK-1 associates with presynaptic membranes at release sites, but not synaptic vesicles.