A new miniMOS tool kit capable of visualizing single copy insertion in C. elegans.

The miniMOS technique has been widely used in the C. elegans community to generate single copy insertions. A worm is considered as a potential insertion candidate if it is resistant to G418 antibiotics and does not express a co-injected fluorescence marker. If the expression of the extrachromosomal array is very low, it is possible for a worm to be mistakenly identified as a miniMOS candidate, as this low expression level can still confer resistance to G418 without producing a detectable fluorescence signal from the co-injection marker. This may increase the workload for identifying the insertion locus in the subsequent steps. In the present study, we modified the plasmid platform for miniMOS insertion by incorporating a myo-2 promoter-driven TagRFP or a ubiquitous H2B::GFP expression cassette into the targeting vector and introducing two loxP sites flanking the selection cassettes. Based on this new miniMOS tool kit, the removable fluorescence reporters can be used to visualize the single copy insertions, greatly reducing insertion locus identification efforts. In our experience, this new platform greatly facilitates the isolation of the miniMOS mutants.

The involvement of oxysterol-binding protein related protein (ORP) 6 in the counter-transport of phosphatidylinositol-4-phosphate (PI4P) and phosphatidylserine (PS) in neurons.

Oxysterol-binding protein (OSBP)-related protein (ORP) 6, a member of subfamily III in the ORP family, localizes to membrane contact sites between the endoplasmic reticulum (ER) and other organelles and functions in non-vesicular exchange of lipids including phosphatidylinositol-4-phosphate (PI4P) in neurons. In this study, we searched for the lipid counter-transported in exchange for PI4P by using molecular cell biology techniques. Deconvolution microscopy revealed that knockdown of ORP6 partially shifted localization of a phosphatidylserine (PS) marker but not filipin in primary cultured cerebellar neurons. Overexpression of ORP6 constructs lacking the OSBP-related ligand binding domain (ORD) resulted in the same shift of the PS marker. A PI4KⅢα inhibitor specifically inhibiting the synthesis and plasma membrane (PM) localization of PI4P, suppressed the localization of ORP6 and the PS marker at the PM. Overexpression of mutant PS synthase 1 (PSS1) inhibited transport of the PS marker to the PM and relocated the PI4P marker to the PM in Neuro-2A cells. Introduction of ORP6 but not the dominant negative ORP6 constructs, shifted the localization of PS back to the PM. These data collectively suggest the involvement of ORP6 in the counter-transport of PI4P and PS.

Effect of long-term confinement on metabolic and physiological parameters in mice.

Long-term and mild confinement or isolation in an enclosed environment can occur in situations such as disasters, specific political, economic or social events, nuclear shelters, seabed exploration, polar expeditions, and space travel. To investigate the effects of stress caused by long-term confinement in an enclosed environment in mammals, we divided 8-week-old C57BL/6J mice into four groups that were housed in a closed environment with a narrow metabolic cage (stress group), normal metabolic cage (control group), conventional cage (conventional group) or conventional cage with wire mesh floor (wire mesh group). The phenotypes of the mice were examined for four weeks, followed by behavioral tests. Weight gain suppression was observed in the stress group. Continuous analysis of these mice every two minutes for four weeks using an implanted measuring device showed a significantly decreased amount of spontaneous activity and subcutaneous temperature in the stress group. After housing in each environment for four weeks, the behavioral tests of mice in the stress group also revealed a shorter latency to fall off in the rotarod test and shorter stride length and interstep distance in the footprint test. Interestingly, the lower spontaneous activity of mice in the stress group was rescued by housing in conventional cages. These results suggest a temporary effect of long-term confinement in an enclosed environment as a chronic and mild stress on homeostasis in mammals.

The Atypical Kinesin KIF26A Facilitates Termination of Nociceptive Responses by Sequestering Focal Adhesion Kinase.

Kinesin superfamily proteins (KIFs) are molecular motors that typically alter the subcellular localization of their cargos. However, the atypical kinesin KIF26A does not serve as a motor but can bind microtubules and affect cellular signaling cascades. Here, we show that KIF26A maintains intracellular calcium homeostasis and negatively regulates nociceptive sensation. Kif26a-/- mice exhibit intense and prolonged nociceptive responses. In their primary sensory neurons, excessive inhibitory phosphorylation of plasma membrane Ca2+ ATPase (PMCA) mediated by focal adhesion kinase (FAK) rendered the Ca transients resistant to termination, and the peripheral axonal outgrowth was significantly enhanced. Upstream, KIF26A is directly associated with a FERM domain of FAK and antagonizes FAK function in integrin-Src family kinase (SFK)-FAK signaling, possibly through steric hindrance and localization to cytoplasmic microtubules.

Oxysterol-binding protein-related protein (ORP) 6 localizes to the ER and ER-plasma membrane contact sites and is involved in the turnover of PI4P in cerebellar granule neurons.

Oxysterol-binding protein (OSBP)-related proteins (ORPs) are conserved lipid binding proteins found in organisms ranging from yeast to mammals. Recent findings have indicated that these proteins mainly localize to contact sites of 2 different membranous organelles. ORP6, a member of the ORP subfamily III, is one of the least studied ORPs. Using approaches in molecular cell biology, we attempted to study the characteristics of ORP6 and found that ORP6 is abundantly expressed in mouse cultured neurons. Deconvolution microscopy of cultured cerebellar granular cells revealed that ORP6 is localized to the endoplasmic reticulum (ER) and ER-plasma membrane (PM) contact sites, where it co-localized with extended synaptotagmin2 (E-Syt2), a well-known ER-PM contact site marker. E-Syt2 also co-localized with ORP3, another subfamily III member, and ORP5, a subfamily IV member. However, ORP5 does not distribute to the same ER-PM contact sites as subfamily III members. Also, the co-expression of ORP3 but not ORP5 altered the distribution of ORP6 into the processes of cerebellar neurons. Immunoprecipitation demonstrated binding between the intermediate region of ORP6 and ORP3 or ORP6 itself. Additionally, the localization of ORP6 in the PM decreased when co-expressed with the intermediate region of ORP6, in which the pleckstrin homology (PH) domain and OSBP-related ligand binding domain (ORD) are deleted. Over-expression of this intermediate region shifted the location of a phophtidylinositol-4-phosphate (PI4P) marker from the Golgi to the PM. Knockdown of ORP6 resulted in the same shift of the PI4P marker. Collectively, our data suggests that the recruitment of ORP6 to ER-PM contact sites is involved in the turnover of PI4P in cerebellar granular neurons.

KIF2A regulates the development of dentate granule cells and postnatal hippocampal wiring.

Kinesin super family protein 2A (KIF2A), an ATP-dependent microtubule (MT) destabilizer, regulates cell migration, axon elongation, and pruning in the developing nervous system. KIF2A mutations have recently been identified in patients with malformed cortical development. However, postnatal KIF2A is continuously expressed in the hippocampus, in which new neurons are generated throughout an individual's life in established neuronal circuits. In this study, we investigated KIF2A function in the postnatal hippocampus by using tamoxifen-inducible Kif2a conditional knockout (Kif2a-cKO) mice. Despite exhibiting no significant defects in neuronal proliferation or migration, Kif2a-cKO mice showed signs of an epileptic hippocampus. In addition to mossy fiber sprouting, the Kif2a-cKO dentate granule cells (DGCs) showed dendro-axonal conversion, leading to the growth of many aberrant overextended dendrites that eventually developed axonal properties. These results suggested that postnatal KIF2A is a key length regulator of DGC developing neurites and is involved in the establishment of precise postnatal hippocampal wiring.

The Molecular Motor KIF1A Transports the TrkA Neurotrophin Receptor and Is Essential for Sensory Neuron Survival and Function.

KIF1A is a major axonal transport motor protein, but its functional significance remains elusive. Here we show that KIF1A-haploinsufficient mice developed sensory neuropathy. We found progressive loss of TrkA(+) sensory neurons in Kif1a(+/-) dorsal root ganglia (DRGs). Moreover, axonal transport of TrkA was significantly disrupted in Kif1a(+/-) neurons. Live imaging and immunoprecipitation assays revealed that KIF1A bound to TrkA-containing vesicles through the adaptor GTP-Rab3, suggesting that TrkA is a cargo of the KIF1A motor. Physiological measurements revealed a weaker capsaicin response in Kif1a(+/-) DRG neurons. Moreover, these neurons were hyposensitive to nerve growth factor, which could explain the reduced neuronal survival and the functional deficiency of the pain receptor TRPV1. Because phosphatidylinositol 3-kinase (PI3K) signaling significantly rescued these phenotypes and also increased Kif1a mRNA, we propose that KIF1A is essential for the survival and function of sensory neurons because of the TrkA transport and its synergistic support of the NGF/TrkA/PI3K signaling pathway.

Cordycepin induces apoptosis and autophagy in human neuroblastoma SK-N-SH and BE(2)-M17 cells.

Cordycepin, also termed 3'-deoxyadenosine, is a derivative of the nucleoside adenosine that represents a potential novel class of anticancer drugs targeting the 3' untranslated region of RNAs. Cordycepin has been reported to induce apoptosis in certain cancer cell lines, but the effects of cordycepin on human neuroblastoma cells have not been studied. In the present study, an MTT assay revealed that cordycepin inhibits the viability of neuroblastoma SK-N-SH and BE(2)-M17 cells in a dose-dependent manner. In addition, cordycepin increases the early-apoptotic cell population of SK-N-SH cells, as determined by fluorescence-activated cell sorting analysis. The induction of apoptosis in neuroblastoma cells by cordycepin was further confirmed by western blotting, which revealed cleavage of caspase-3 and poly(adenosine diphosphate-ribose) polymerase 1 in the SK-N-SH and BE(2)-M17 cells. Cordycepin also induced the formation of a punctate pattern of light-chain 3 (LC3)-associated green fluorescence in the SK-N-SH cells transfected with a pEGFP-LC3 vector. Furthermore, western blotting revealed cleavage of LC3 A/B in cordycepin-treated neuroblastoma SK-N-SH cells. Taken together, the results indicate that cordycepin significantly increases apoptosis and autophagy in neuroblastoma cells, and may therefore be a drug candidate for neuroblastoma therapy, but requires additional evaluation.

A molecular motor, KIF13A, controls anxiety by transporting the serotonin type 1A receptor.

Molecular motors are fundamental to neuronal morphogenesis and function. However, the extent to which molecular motors are involved in higher brain functions remains largely unknown. In this study, we show that mice deficient in the kinesin family motor protein KIF13A (Kif13a(-/-) mice) exhibit elevated anxiety-related behavioral phenotypes, probably because of a reduction in 5HT(1A) receptor (5HT(1A)R) transport. The cell-surface expression level of the 5HT(1A)R was reduced in KIF13A-knockdown neuroblastoma cells and Kif13a(-/-) hippocampal neurons. Biochemical analysis showed that the forkhead-associated (FHA) domain of KIF13A and an intracellular loop of the 5HT(1A)R are the interface between the motor and cargo vesicles. A minimotor consisting of the motor and FHA domains is able to transport 5HT(1A)R-carrying organelles in in vitro reconstitution assays. Collectively, our results suggest a role for this molecular motor in anxiety control.

KIF26A is an unconventional kinesin and regulates GDNF-Ret signaling in enteric neuronal development.

The kinesin superfamily proteins (KIFs) are motor proteins that transport organelles and protein complexes in a microtubule- and ATP-dependent manner. We identified KIF26A as a new member of the murine KIFs. KIF26A is a rather atypical member as it lacks ATPase activity. Mice with a homozygous deletion of Kif26a developed a megacolon with enteric nerve hyperplasia. Kif26a-/- enteric neurons showed hypersensitivity for GDNF-Ret signaling, and we find that KIF26A suppressed GDNF-Ret signaling by direct binding and inhibition of Grb2, an essential component of GDNF/Akt/ERK signaling. We therefore propose that the unconventional kinesin KIF26A plays a key role in enteric nervous system development by repressing a cell growth signaling pathway.