InteractiveFly: GeneBrief

sunday driver: Biological Overview | References

Highlighting the importance of proper intracellular organization, many muscle diseases are characterized by mispositioned myonuclei. Proper positioning of myonuclei is dependent upon the microtubule motor proteins, Kinesin-1 and cytoplasmic Dynein, and there are at least two distinct mechanisms by which Kinesin and Dynein move myonuclei. The motors exert forces both directly on the nuclear surface and from the cell cortex via microtubules. How these activities are spatially segregated yet coordinated to position myonuclei is unknown. Using Drosophila melanogaster, Sunday Driver (Syd), a homolog of mammalian JNK-interacting protein 3 (JIP3), was shown to specifically regulate Kinesin- and Dynein-dependent cortical pulling of myonuclei without affecting motor activity near the nucleus. Specifically, Syd mediates Kinesin-dependent localization of Dynein to the muscle ends, where cortically anchored Dynein then pulls microtubules and the attached myonuclei into place. Proper localization of Dynein also requires activation of the JNK signaling cascade. Furthermore, Syd functions downstream of JNK signaling because without Syd, JNK signaling is insufficient to promote Kinesin-dependent localization of Dynein to the muscle ends. The significance of Syd-dependent myonuclear positioning is illustrated by muscle-specific depletion of Syd, which impairs muscle function. Moreover, both myonuclear spacing and locomotive defects in syd mutants can be rescued by expression of mammalian JIP3 in Drosophila muscle tissue, indicating an evolutionarily conserved role for JIP3 in myonuclear movement and highlighting the utility of Drosophila as a model for studying mammalian development. Collectively, this study implicated Syd/JIP3 as a novel regulator of myogenesis that is required for proper intracellular organization and tissue function (Schulman, 2014).

The intracellular location of the multiple nuclei within muscle cells has recently gained traction as a potential contributing factor to muscle disease. Improper myonuclear position strongly correlates with muscle disease and muscle weakness; yet, the mechanisms of myonuclear movement and positioning have only recently begun to emerge (Schulman, 2014).

Recent work in Drosophila has identified myonuclear positioning as a microtubule-dependent process (Metzger, 2012: Elhanany-Tamir, 2016), requiring both Kinesin-1 (Kinesin) and cytoplasmic Dynein (Dynein), the plus- and minus-end directed microtubule motor proteins, respectively (Metzger, 2012; Folker, 2012; Folker, 2014). Specifically, two spatially distinct Kinesin- and Dynein-dependent processes position myonuclei. Firstly, Kinesin and Dynein exert forces directly on the nucleus: Kinesin extends the front of the myonucleus in the direction of travel, and Dynein is necessary for the retraction of the trailing edge of the myonucleus to complete a translocation step. Secondly, Kinesin transports Dynein to the cell cortex near the ends of the muscles where Dynein then pulls microtubule minus-ends and the attached myonuclei into place. Disruption of either pathway leads to mispositioned myonuclei, but how Kinesin and Dynein are both used in two spatially segregated mechanisms, and whether their actions in these two different locations are connected or interdependent, is not known (Schulman, 2014).

In many cellular contexts, adaptor proteins specify a variety of motor protein functions. Adaptors either recruit or restrict motors to particular cellular locations, mediate specific motor-cargo interactions, ensure proper temporal and spatial activation of motor function, or enhance motor processivity. Additionally, adaptor proteins that influence motor function respond to distinct stimuli. Some adaptor proteins regulate motors in response to physical changes of the cell brought on by mechanical strain, while others respond to environmental cues via the induction of signaling cascades. Thus, adaptors are ideal candidates to direct the activities of Kinesin and Dynein during myonuclear positioning (Schulman, 2014 and references therein).

The JNK signaling cascade is one of three classical mitogen-activated protein kinase (MAPK) cascades conserved across eukaryotes. Each cascade consists of a MAPK kinase kinase -> MAPK kinase -> MAPK signaling module that impacts various cellular functions in response to specific stimuli. One function of the JNK MAPK signaling cascade is to phosphorylate JNK-interacting proteins (JIPs), a class of adaptor proteins that regulate Kinesin and Dynein activity in neurons. While all JIPs interact with both Kinesin and Dynein, each adaptor has unique motor-binding domains. JIP1/2 proteins contain a shared motor-binding domain, while JIP3/4 family members have separate Kinesin- and Dynein-binding domains that facilitate binding to both motors simultaneously; thus, different JIPs coordinate motor functions via distinct mechanisms. Given these features, the JIP proteins could regulate the two Kinesin- and Dynein-dependent pathways governing myonuclear positioning (Schulman, 2014).

To address this possibility, this study examined the role of the JIP3 ortholog, Sunday Driver (Syd), during Drosophila muscle morphogenesis. Syd was found to respond to the activation of the JNK signaling cascade to regulate myonuclear positioning by specifically promoting Kinesin-dependent localization of Dynein to the muscle ends. Furthermore, it is proposed that Kinesin and Dynein are both initially perinuclear and that Syd specifies a subset of Kinesin to relocate Dynein to the muscle cell cortex to initiate cortical pulling of myonuclei. Finally, this study demonstrates that disrupted JNK signaling or loss of Syd decreases muscle function, indicating that proper regulation of the JNK signaling cascade and the JIP adaptor proteins is not only necessary for intracellular organization but also critical for muscle function (Schulman, 2014).

This study has used the Drosophila musculature to elucidate the cellular mechanisms and signaling pathways that impact myonuclear position in vivo. The stereotypic distribution of evenly spaced myonuclei is disrupted in embryos and larvae mutant for Sunday Driver (Syd), an adaptor protein known to regulate Kinesin and Dynein activity in neurons. Syd is expressed and required in muscle tissue to regulate motor activity during myonuclear positioning. Moreover, while Kinesin and Dynein are known to influence myonuclear position via two spatially distinct mechanisms, this study demonstrates that Syd specifically regulates these motors in the context of cortical pulling at the muscle end without affecting motor activity at the nuclear surface (see Model of Syd-dependent myonuclear positioning). Syd is a member of the JNK-interacting protein (JIP) family, and this study demonstrates that JNK signaling is required for Kinesin- and Syd-dependent localization of Dynein to the muscle ends, which facilitates Dynein-based cortical pulling of myonuclei. Moreover, in the absence of Syd, both Kinesin and Dynein accumulate near the nucleus, where the motors are known to influence nuclear shape changes/dynamics to promote myonuclear translocation. Syd has no impact on nuclear dynamics; thus, it is proposed that, via instructive JNK signaling, Syd specifies and activates a population of Kinesin at the nucleus to relocate Dynein to the muscle ends to initiate cortical pulling of myonuclei. Finally, loss of Syd and disruption of JNK signaling impairs locomotive ability, indicating that Syd-dependent myonuclear positioning is critical for muscle function (Schulman, 2014).

The finding that JNK signaling is required for this process is novel and significant. Prior to this study, work to elucidate the process of myonuclear positioning focused on identifying factors required for the physical mechanics of moving myonuclei through the cell. However, the present work newly identifies intracellular signals that regulate these activities. Specifically, it was shown that JNK signaling is required for Kinesin- and Syd-dependent localization of Dynein to the muscle ends. What remains unclear is whether JNK-mediated phosphorylation of Syd induces/permits Dynein binding to Kinesin or if a trimolecular Kinesin-Syd-Dynein complex forms prior to JNK signaling-dependent activation of Kinesin motor activity, which, in turn, transports Dynein to the muscle ends and leads to cortical pulling and proper positioning of myonuclei (Schulman, 2014).

Regardless, these data are consistent with Syd being necessary to relay this instructive JNK signal. Specifically, the C-terminus of Syd is critical for this transport, as Kinesin, Dynein, and truncated Syd are all found near the nucleus in syd mutants, which express N-terminal fragments of Syd. This finding was initially unexpected because the minimal domains of Syd required for binding to Kinesin, Dynein, and JNK are all located in the N-terminus. Furthermore, the N-terminus of Syd is sufficient to support Kinesin-based transport in vitro. However, the C-terminus of Syd is more highly conserved than the well-annotated N-terminus, and biochemical analysis of JIP3 demonstrates that upstream components of the JNK MAPK signaling pathway bind to C-terminal regions of JIP3. Consistent with these data, mutants lacking the C-terminus of Syd failed to promote proper transport of Dynein to the muscle ends despite normal JNK signaling in these backgrounds. This argues that both the N- and C-termini of Syd are necessary to relay instructive cues from the JNK signaling cascade, which leads to proper myonuclear positioning (Schulman, 2014).

Interestingly, while JNK signaling is indeed necessary for myonuclear positioning, it was also demonstrated that constitutively active JNK signaling impairs this process. Despite the inconsistent phenotype, overall decreased amounts of Dynein are found at the muscle ends when Hep-Act is expressed in the muscles. This suggests that overactive JNK signaling either mildly impairs Dynein transport, or alternatively, prevents the maintenance of Dynein at the muscle end. The latter interpretation is favored based on the observation that increased levels of Syd are found at the muscle end when JNK signaling is overactivated. This suggests that efficient transport, and likely excess transport, indeed occurs in embryos expressing Hep-Act. This activity would transport Dynein to the muscle ends; thus, overactive JNK signaling likely inhibits the maintenance of Dynein at this location (Schulman, 2014).

It is not clear how this inhibition could occur; however, one possibility is that failure to dephosphorylate Syd may impair the ability of Dynein to associate with ARF6-GTP, a membrane-bound protein that binds to JIP3/4 proteins (Montagnac, 2009). ARF6-GTP and Klc compete for binding to JIP3, and phosphorylated JIPs preferentially bind and activate Kinesin. However, JIP3–ARF6-GTP interactions enhance binding between ARF6-GTP and Dynactin, a well-known Dynein-interacting protein. Thus, in this model, once the Kinesin-Syd-Dynein complex reaches the cell cortex, perhaps Syd must lose the JNK signal and become dephosphorylated to dissociate from Kinesin and bind to ARF6-GTP. This may facilitate hand-off of Dynein to ARF6-GTP, which would aid in securing Dynein to the muscle end (Schulman, 2014).

Although the details of this final step remain unclear, the model (see Model of Syd-dependent myonuclear positioning) likely represents a common mechanism by which Syd and other JIP3 orthologs act. Analogous to the proposed manner in which Syd selects certain Kinesin complexes to initiate transport, the C. elegans ortholog of Syd/JIP3, UNC-16, was found to exhibit similar gatekeeper characteristics by designating specific complexes to initiate axonal transport in neurons (Edwards, 2013). Furthermore, once specified, UNC-16 also mediates Kinesin-dependent transport of Dynein to the ends of nerve processes. Similarly, mammalian JIP proteins mediate Kinesin-driven transport of many large cargoes, including Dynein. Finally, Syd, UNC-16, and JIP3 directly bind to Kinesin heavy and light chains, and all three orthologs bind to p50 and p150^Glued, components of the Dynactin complex, a well-known regulator of Dynein. Together these data, these observations collectively suggest that this mechanism of JIP3-mediated motor coordination is well conserved across species and tissues (Schulman, 2014 and references therein).

These findings are interesting given that Kinesin and Dynein can directly interact in vitro; however, adaptors such as Syd and other JIP proteins are likely required to mediate motor protein interactions to direct specific motor functions in vivo. Consistent with this notion, structural differences between the JIP1/2 subfamily and the JIP3/4 subfamily of proteins impact how each JIP binds to Kinesin and Dynein and influences motor activity. Although these different JIPs can cooperate towards a single goal, they often have unique roles and cannot fully compensate for loss of another in vivo (Schulman, 2014).

In Drosophila, Syd is the only ortholog of the JIP3/4 family of proteins. Similarly, there is only one ortholog of the JIP1/2 family of proteins, Aplip1. Thus, in the context of myonuclear positioning, it is tempting to speculate that while Syd modulates motor activity to promote cortical pulling of myonuclei, perhaps Aplip1 affects the ability of the motors to regulate nuclear dynamics. Furthermore, perhaps JNK signaling is the necessary switch that shifts motor function from one mechanism to the other. Indeed, work in Drosophila neurons shows that activation of the JNK signaling cascade disrupts the association between Aplip1 (JIP1) and Kinesin (Horiuchi, 2007), and this study shows that JNK signaling is required for coordinated Kinesin-Syd (JIP3) function in the cortical pulling pathway of myonuclear positioning (Schulman, 2014).

Regarding the biological relevance of Syd-dependent mechanisms, this study demonstrates that Syd and proper regulation of JNK signaling are critical for muscle function. RNAi-mediated loss of Syd specifically in the muscles leads to decreased larval velocity, and similar locomotive dysfunction is observed in larvae with muscle-specific disruptions in JNK signaling. Consistent with previous reports, this study shows that these locomotive defects are not due to impaired communication with the CNS, but rather correlate with mispositioned myonuclei. These analyses further revealed that muscle-specific disruptions of the JNK signaling cascade additionally impair muscle length/growth, which can also affect locomotion. These findings indicate that JNK signaling is, not surprisingly, necessary for multiple aspects of muscle development. However, that similar concomitant defects are not observed in larvae lacking Syd argues that the role of Syd is more specific to mechanisms of myonuclear positioning. Finally, muscle-specific expression of mammalian JIP3 simultaneously restored myonuclear spacing and rescued larval crawling defects in larvae lacking Syd. These data highlight the high degree of conservation across species, emphasize the muscle autonomous role of Syd, and reiterate the strong correlation between mispositioned myonuclei and decreased muscle output observed previously. In sum, this study has identified that JNK signaling and the motor adaptor, Syd, are required for influencing specific functions of Kinesin and Dynein that lead to proper myonuclear positioning and muscle function, which has significant implications for muscle cell organization, development, and disease (Schulman, 2014).

Sunday Driver/JIP3 binds kinesin heavy chain directly and enhances its motility

Neuronal development, function and repair critically depend on axonal transport of vesicles and protein complexes, which is mediated in part by the molecular motor kinesin-1. Adaptor proteins recruit kinesin-1 to vesicles via direct association with kinesin heavy chain (KHC), the force-generating component, or via the accessory light chain (KLC). Binding of adaptors to the motor is believed to engage the motor for microtubule-based transport. This study, carried out in mice, reports that the adaptor protein Sunday Driver (syd, also known as JIP3 or JSAP1) interacts directly with KHC, in addition to and independently of its known interaction with KLC. Using an in vitro motility assay, it was shown that syd activates KHC for transport and enhances its motility, increasing both KHC velocity and run length. syd binding to KHC is functional in neurons, as syd mutants that bind KHC but not KLC are transported to axons and dendrites similarly to wild-type syd. This transport does not rely on syd oligomerization with itself or other JIP family members. These results establish syd as a positive regulator of kinesin activity and motility (Sun, 2011).

To further understand KHC function within neurons, this examined the interaction of KHC with the adaptor protein Sunday Driver (syd). syd was identified in Drosophila in a genetic screen for axonal transport mutants and was shown to interact directly with KLC (Bowman, 2000). syd is a member of the JIP family of proteins, which interact with the c-Jun N-terminal kinase (JNK), and is thus also known as JIP3 (Kelkar, 2000) or JSAP1 (Ito, 1999). The C. elegans homologue of syd/JIP3 (unc-16) also integrates JNK signalling and kinesin-1-dependent transport (Byrd, 2001; Sakamoto, 2005). All known JIP family members interact with KLC (Bowman, 2000; Verhey, 2001; Kelkar, 2005; Nguyen, 2005; Sakamoto et al, 2005). The interaction between syd and KLC relies on syd's Leucine-Zipper (LZ) domain and on the KLC tetratricopeptide repeats (TPR domains) (Kelkar, 2005; Nguyen, 2005; Hammond, 2008). Given its interaction with kinesin, Syd was proposed to mediate the axonal transport of at least one class of vesicles (Bowman, 2000). In C. elegans, syd/unc16 is involved in synaptic vesicle localization (Byrd, 2001; Sakamoto, 2005) and in synaptic membrane trafficking (Brown, 2009). Recently, two different vesicle populations—endosomes and small anterogradely moving organelles were identified as syd cargoes in mouse axons (Abe, 2009). This sstudy shows that syd interacts directly with the tail domain of KHC in addition to and independently of its interaction with KLC. Using an in vitro motility assay, syd was shown to activate KHC for microtubule-based transport and promotes efficient motility of KHC along microtubules, increasing both processive run length and velocity. Importantly, syd binding to KHC is functional in neurons, as syd mutants that bind KHC but not KLC are transported to axons and dendrites similarly to wild-type syd. syd's KHC-dependent transport does not rely on oligomerization with endogenous JIP family members. This work establishes syd as an adaptor for both kinesin-1 chains and as a positive regulator of kinesin-1 motility (Sun, 2011).

Syd, a previously known KLC adaptor, is also capable of interacting directly with KHC independently of KLC. Binding of syd to KHC not only activates kinesin-1 for microtubule-dependent transport, but also enhances KHC velocity and run length. Binding of syd to KHC is functional in neurons, since mutant syd that interacts with KHC only is targeted to axons and dendrites similarly to wt syd. Thus, syd-KHC interaction promotes transport but does not appear to determine transport specificity. Together, these data establish syd as a novel KHC binding partner capable of positively regulating kinesin-1 motility (Sun, 2011).

Kinesin-1 is a processive motor, which takes multiple steps along microtubules before dissociating. How kinesin-1 activation for microtubule transport is controlled in live cells is not well understood, but recent studies couple kinesin-1 activation for microtubule transport with the binding of cellular partners. A proposed regulatory mechanism for kinesin-1 activation is the transition from a "folded" inactive state to an "open" active state. In the inactive folded conformation, the KHC tail domain interacts with both the motor domain and the microtubules to prevent kinesin motion. Activation of kinesin-1 for transport requires a conformational change in which motor and tail domains are separated and the motor domains come closer together. in vitro motility results indicate that syd, but not sydΔKBD, which lacks the KHC binding domain, increased the number of motile events, suggesting that syd binding to the KHC tail domain efficiently relieves the inhibition by the KHC tail domain, activating or opening KHC to bind microtubules for long-range motility. These results place syd alongside Pat1 as cellular regulators of kinesin-1 activity (Sun, 2011).

In the case of tetrameric kinesin-1, it has been proposed that binding of both KLC and KHC is required for motor activation. It will be interesting to determine in future studies whether syd may fulfill activation of a KHC/KLC complex via its ability to interact with both KHC and KLC. Alternatively, similar to the JIP1–Fez1 complex, syd may require additional interacting partners for the activation of tetrameric kinesin-1 (Sun, 2011).

Kinesin-1 stepping along microtubules is believed to involve concerted conformational change and diffusive movement of the tethered head to the next binding site. The precise mechanisms regulating the speed and the distance that kinesin-1 can achieve are fairly well understood for purified kinesin-1. Yet less is known about how kinesin-1 motility is regulated in a cellular environment. The observation that different kinesin-1 cargoes move at different rates in a cellular environment illustrates the complexity of in vivo motor regulation. The increase in KHC velocity and run length in the presence of full-length syd and syd&Delat;239 suggests that syd binding to the KHC tail relieve the "brake" provided by the tail binding to the microtubule, thus allowing efficient forward movement. A recent study indicates that the Drosophila Pat1 protein interacts with KHC and functions as a positive regulator of KHC motility for the transport of oskar mRNA and dynein in Drosophila oocytes. In the absence of Pat1, both kinesin-1 velocity and run length are reduced. The Ran binding protein 2 (RanBP2) activates the ATPase activity of KHC, suggesting that RanBP2 may also regulate kinesin-1 velocity and processivity. These observations support the notion that adaptors contribute to regulate kinesin-1 motile properties, in addition to their roles in recruiting cargoes (Sun, 2011).

The results indicate that murine syd is capable of associating with both tetrameric and dimeric kinesin-1. This result is consistent with studies indicating that kinesin-1 exists and functions as a dimer of two heavy chains lacking the light chains, in addition to its conventional tetrameric conformation. KLC-independent transport has been reported for mitochondria, syntaxin-containing vesicles, and RNA particles, in agreement with earlier studies reporting that KHC dimers can bind membrane organelles in the absence of KLC. Furthermore, a small pool of KHC not associated with KLC has been found in cultured HeLa cells and bovine brain and this study obtained similar results from mouse brain. Degradation of KLC during kinesin-1 isolation can be excluded, since KLC in was detected in this experiment. Furthermore, significant molar excess of KHC over KLC has been reported in CV-1 cells. It is thus conceivable that spatially and temporally, KHC and KLC do not always fully colocalize. Indeed, it has been shown that KLC is absent in photoreceptor cells and that throughout the retina, KLC does not fully colocalize with KHC, suggesting that at the cellular and subcellular levels KHC localization does not fully overlap with KLC. In addition, during brain development, KHC and KLC decline after the first week of postnatal life, but the decline in KLC appears to be more pronounced. Therefore, it is possible that syd interacts with tetrameric kinesin-1 via KLC, while in cells or subcellular regions where KLC is absent syd instead interacts and regulates the activity of a kinesin-1 dimer. The current observation that syd interacts with KHC in addition to and independently from its known interaction with KLC is not inconsistent with the data published so far. In C. elegans, the localization of UNC-16 (syd) depends on both UNC-116 (KHC) and KLC. Furthermore, syd transport to neurite tips in differentiated CAD cells is mostly, but not completely dependent on KLC. Similarly to syd, the FMRP was found to bind KLC, and also KHC in a KLC-independent manner (Sun, 2011 and references therein).

Kinesin-1 drives different sets of cargoes to axons or dendrites, but how kinesin-1 distinguishes between axonal or dendritic cargoes for directional sorting remains poorly understood. Previous studies suggested that there was a dendritic preference for KHC cargoes and an axonal preference for KLC linkage. The current results showed that regardless of its mode of association with kinesin-1, murine syd is predominantly targeted to axon tips. It is thus more likely that the uploaded cargoes, and not the adaptor-motor complexes, determine the destination of kinesin-1 and its adaptor. Recent studies have shown that murine syd mediates the transport of at least two distinct types of vesicles in axons: endosomes and small anterogradely moving vesicles. It will be interesting to define in future studies the nature of the syd cargoes transported by KLC-dependent or KLC-independent interaction. Indeed, KLC isoforms have been proposed to mediate targeting of KHC to proper cargo, but KHC can also associate with membranous cargo in the absence of KLC (Sun, 2011 and references therein).

The propensity of JIP family members to form homo or hetero-oligomers suggests that syd may be transported via oligomerization. Indeed, Hammond (2008) reported that syd and JIP1 require each other for efficient transport of JIP1 or syd in non-neuronal cells. Such cooperative transport is due to an interaction between JIP1 and syd as well as distinct binding sites on the KLC-TPR domain. This study found that despite its ability to oligomerize with myc-JIP1, GFP-sydΔΔ failed to exit the cell body. Thus, GFP–sydΔΔ may be unable to be stably incorporated in a complex with JIP1 and KLC. Oligomerization with JIP1 may thus not fully account for the transport of the syd mutant GFP–syd3–239 lacking the KLC binding domain. Although it cannot be excluded that other yet unknown kinesin-1 binding proteins may be involved in syd transport in neurons, the results suggest that syd's interaction with KHC may promote transport in neurons and that oligomerization may provide additional layers of regulation of syd-dependent transport (Sun, 2011).

In summary, this study has identified syd as an adaptor for kinesin-1 heavy chain, and it was determined that syd enhances KHC motility along microtubules. Future studies are needed to determine the precise mechanisms by which syd regulates kinesin-1 activation and processivity, and examine whether the distinct modes of syd interaction with kinesin-1 provide specificity for cargo selection and delivery to particular subcelullar destinations (Sun, 2011).

Sunday Driver links axonal transport to damage signaling

Neurons transmit long-range biochemical signals between cell bodies and distant axonal sites or termini. To test the hypothesis that signaling molecules are hitchhikers on axonal vesicles, this study focused on the murine c-Jun NH2-terminal kinase (JNK) scaffolding protein Sunday Driver (Syd), which has been proposed to link the molecular motor protein kinesin-1 to axonal vesicles. Syd and JNK3 are present on vesicular structures in axons, are transported in both the anterograde and retrograde axonal transport pathways, and interact with Kinesin-I and the Dynactin complex. Nerve injury induces local activation of JNK, primarily within axons, and activated JNK and syd are then transported primarily retrogradely. In axons, Syd and activated JNK colocalize with p150Glued, a subunit of the dynactin complex, and with Dynein. Finally, injury was found to induce an enhanced interaction between Syd and Dynactin. Thus, a mobile axonal JNK-Syd complex may generate a transport-dependent axonal damage surveillance system (Cavalli, 2005).

UNC-16, a JNK-signaling scaffold protein, regulates vesicle transport in C. elegans

Transport of synaptic components is a regulated process. Loss-of-function mutations in the C. elegans unc-16 gene result in the mislocalization of synaptic vesicle and glutamate receptor markers. unc-16 encodes a homolog of mouse JSAP1/JIP3 and Drosophila Sunday Driver. Like JSAP1/JIP3, UNC-16 physically interacts with JNK and JNK kinases. Deletion mutations in Caenorhabditis elegans JNK and JNK kinases result in similar mislocalization of synaptic vesicle markers and enhance weak unc-16 mutant phenotypes. unc-116 kinesin heavy chain mutants also mislocalize synaptic vesicle markers, as well as a functional UNC-16::GFP. Intriguingly, unc-16 mutations partially suppress the vesicle retention defect in unc-104 KIF1A kinesin mutants. These results suggest that UNC-16 may regulate the localization of vesicular cargo by integrating JNK signaling and kinesin-1 transport (Byrd, 2001).

Kinesin-dependent axonal transport is mediated by the sunday driver (SYD) protein

A broadly conserved membrane-associated protein required for the functional interaction of kinesin-I with axonal cargo was identified. Mutations in sunday driver (syd) and the axonal transport motor kinesin-I cause similar phenotypes in Drosophila, including aberrant accumulations of axonal cargoes. GFP-tagged mammalian Syd localizes to tubulovesicular structures that costain for kinesin-I and a marker of the secretory pathway. Coimmunoprecipitation analysis indicates that mouse Syd forms a complex with kinesin-I in vivo. Yeast two-hybrid analysis and in vitro interaction studies reveal that Syd directly binds kinesin-I via the tetratricopeptide repeat (TPR) domain of kinesin light chain (KLC) with K(d) congruent with 200 nM. It is proposes that SYD mediates the axonal transport of at least one class of vesicles by interacting directly with KLC (Bowman, 2000).

Search PubMed for articles about Drosophila Sunday driver

Abe, N., Almenar-Queralt, A., Lillo, C., Shen, Z., Lozach, J., Briggs, S. P., Williams, D. S., Goldstein, L. S. and Cavalli, V. (2009). Sunday driver interacts with two distinct classes of axonal organelles. J Biol Chem 284: 34628-34639. PubMed ID: 19801628

Bowman, A. B., et al. (2000). Kinesin-dependent axonal transport is mediated by the sunday driver (SYD) protein. Cell 103: 583-594. 11106729

Brown, H. M., Van Epps, H. A., Goncharov, A., Grant, B. D. and Jin, Y. (2009). The JIP3 scaffold protein UNC-16 regulates RAB-5 dependent membrane trafficking at C. elegans synapses. Dev Neurobiol 69: 174-190. PubMed ID: 19105215

Byrd, D. T., Kawasaki, M., Walcoff, M., Hisamoto, N., Matsumoto, K. and Jin, Y. (2001). UNC-16, a JNK-signaling scaffold protein, regulates vesicle transport in C. elegans. Neuron 32: 787-800. PubMed ID: 11738026

Cavalli, V., Kujala, P., Klumperman, J. and Goldstein, L. S. (2005). Sunday Driver links axonal transport to damage signaling. J Cell Biol 168: 775-787. PubMed ID: 15738268

Edwards, S. L., Yu, S. C., Hoover, C. M., Phillips, B. C., Richmond, J. E. and Miller, K. G. (2013). An organelle gatekeeper function for Caenorhabditis elegans UNC-16 (JIP3) at the axon initial segment. Genetics 194: 143-161. PubMed ID: 23633144

Elhanany-Tamir, H., Yu, Y. V., Shnayder, M., Jain, A., Welte, M. and Volk, T. (2012). Organelle positioning in muscles requires cooperation between two KASH proteins and microtubules. J Cell Biol 198: 833-846. PubMed ID: 22927463

Folker, E. S., Schulman, V. K. and Baylies, M. K. (2012). Muscle length and myonuclear position are independently regulated by distinct Dynein pathways. Development 139: 3827-3837. PubMed ID: 22951643

Folker, E. S., Schulman, V. K. and Baylies, M. K. (2014). Translocating myonuclei have distinct leading and lagging edges that require kinesin and dynein. Development 141: 355-366. PubMed ID: 24335254

Hammond, J. W., Griffin, K., Jih, G. T., Stuckey, J. and Verhey, K. J. (2008). Co-operative versus independent transport of different cargoes by Kinesin-1. Traffic 9: 725-741. PubMed ID: 18266909

Horiuchi, D., Collins, C. A., Bhat, P., Barkus, R. V., Diantonio, A. and Saxton, W. M. (2007). Control of a kinesin-cargo linkage mechanism by JNK pathway kinases. Curr Biol 17: 1313-1317. PubMed ID: 17658258

Kelkar, N., Gupta, S., Dickens, M. and Davis, R. J. (2000). Interaction of a mitogen-activated protein kinase signaling module with the neuronal protein JIP3. Mol Cell Biol 20: 1030-1043. PubMed ID: 10629060

Ito, M., Yoshioka, K., Akechi, M., Yamashita, S., Takamatsu, N., Sugiyama, K., Hibi, M., Nakabeppu, Y., Shiba, T. and Yamamoto, K. I. (1999). JSAP1, a novel jun N-terminal protein kinase (JNK)-binding protein that functions as a Scaffold factor in the JNK signaling pathway. Mol Cell Biol 19: 7539-7548. PubMed ID: 10523642

Metzger, T., Gache, V., Xu, M., Cadot, B., Folker, E. S., Richardson, B. E., Gomes, E. R. and Baylies, M. K. (2012). MAP and kinesin-dependent nuclear positioning is required for skeletal muscle function. Nature 484: 120-124. PubMed ID: 22425998

Montagnac, G., Sibarita, J. B., Loubery, S., Daviet, L., Romao, M., Raposo, G. and Chavrier, P. (2009). ARF6 Interacts with JIP4 to control a motor switch mechanism regulating endosome traffic in cytokinesis. Curr Biol 19: 184-195. PubMed ID: 19211056

Nguyen, Q., Lee, C. M., Le, A. and Reddy, E. P. (2005). JLP associates with kinesin light chain 1 through a novel leucine zipper-like domain. J Biol Chem 280: 30185-30191. PubMed ID: 15987681

Sakamoto, R., Byrd, D. T., Brown, H. M., Hisamoto, N., Matsumoto, K. and Jin, Y. (2005). The Caenorhabditis elegans UNC-14 RUN domain protein binds to the kinesin-1 and UNC-16 complex and regulates synaptic vesicle localization. Mol Biol Cell 16: 483-496. PubMed ID: 15563606

Schulman, V. K., Folker, E. S., Rosen, J. N. and Baylies, M. K. (2014). Syd/JIP3 and JNK signaling are required for myonuclear positioning and muscle function. PLoS Genet 10: e1004880. PubMed ID: 25522254

Sun, F., Zhu, C., Dixit, R. and Cavalli, V. (2011). Sunday Driver/JIP3 binds kinesin heavy chain directly and enhances its motility. EMBO J 30: 3416-3429. PubMed ID: 21750526

Verhey, K. J., Meyer, D., Deehan, R., Blenis, J., Schnapp, B. J., Rapoport, T. A. and Margolis, B. (2001). Cargo of kinesin identified as JIP scaffolding proteins and associated signaling molecules. J Cell Biol 152: 959-970. PubMed ID: 11238452

date revised: 20 January 2015

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