In addition, while mutations in the rpm-1 pathway produced dramatic effects on presynaptic organization in the DD motoneurons, they did not cause obvious presynaptic abnormalities in DA9 (data not shown). In contrast, arl-8/jkk-1 interaction strongly find more impacts synapse distribution in DDs, DA9, as well as multiple other neuronal types. Therefore, there are so far no data supporting a genetic interaction between the arl-8/jkk-1 and the rpm-1/dlk-1 pathway. Two effectors of ARL8 in regulating lysosomal trafficking were recently identified, including the HOPS complex and the SKIP
protein that links lysosomes to the KIF5 motor complex (Garg et al., 2011; Rosa-Ferreira and Munro, 2011). We have investigated their NSC 683864 mouse potential involvement in presynaptic development. First, human ARL8B was reported to recruit the HOPS complex to direct lysosomal trafficking (Garg et al., 2011). We examined the phenotypes of deletion mutants in two of the core subunits of the HOPS complex in C. elegans, VPS-16 (ok719) and VPS-18 (tm1125), and an accessory subunit, VPS-39 (ok2442). Despite their lysosomal trafficking and/or lethality phenotypes ( Hermann et al., 2005; Kinchen et al., 2008; Xiao et al., 2009), all three mutants appear normal in presynaptic development in DA9 (data not shown). Second, the human SKIP protein was proposed to bind to lysosome-localized
ARL8B and the kinesin light chain, thus linking lysosomes to the KIF5 motor complex ( Rosa-Ferreira and Munro, 2011). Knockdown of ARL8B, SKIP, or KIF5B generated similar changes in lysosome distribution in cultured cells. In the C. elegans genome, the gene Y51H1A.2 encodes the only protein sharing limited sequence homology with SKIP. However, a deletion mutation in this gene (K. Kontani, personal communication) did not cause abnormal SV protein localization (data not shown). In addition, loss-of-function mutations in Urease klc-1 and klc-2, which encode the only two kinesin light chains in C. elegans, did not phenocopy arl-8 in DA9, nor did they enhance or suppress the arl-8 phenotype (data not shown). Furthermore, loss of function
in UNC-116/KIF5 did not cause an arl-8-like presynaptic phenotype in DA9 either (data not shown). Collectively, these findings suggest that the JNK pathway represents a mechanism that strongly interacts with arl-8 in regulating presynaptic patterning. It has been suggested that SV and AZ proteins are sorted into different vesicular cargoes at the Golgi. While SV proteins are transported in STVs (Matteoli et al., 1992; Ahmari et al., 2000; Tao-Cheng, 2007), the PTVs are thought to carry AZ material in vertebrate neurons (Zhai et al., 2001; Shapira et al., 2003; Maas et al., 2012). Interestingly, live imaging combined with retrospective EM analysis revealed that STVs are in proximity to dense core vesicles in the axon of cultured neurons (Ahmari et al., 2000).