Chemical identification of an active component and putative neural mechanism for repellent effect of a native ant's odor on invasive species.

The invasive Argentine ants (Linepithema humile) and the red imported fire ants (Solenopsis invicta) constitute a worldwide threat, causing severe disruption to ecological systems and harming human welfare. In view of the limited success of current pest control measures, we propose here to employ repellents as means to mitigate the effect of these species. We demonstrate that cuticular hydrocarbons (CHCs) used as nestmate-recognition pheromone in the Japanese carpenter ant (Camponotus japonicus), and particularly its (Z)-9-tricosene component, induced vigorous olfactory response and intense aversion in these invasive species. (Z)-9-Tricosene, when given to their antennae, caused indiscriminate glomerular activation of antennal lobe (AL) regions, creating neural disarray and leading to aversive behavior. Considering the putative massive central neural effect, we suggest that the appropriate use of certain CHCs of native ants can facilitate aversive withdrawal of invasive ants.

Opsins in the Cephalic and Extracephalic Photoreceptors in the Marine Gastropod Onchidium verruculatum.

AbstractThe marine gastropod Onchidium verruculatum has a pair of ocular photoreceptors, the stalk eyes, on the tip of its stalk near the head, as well as several extracephalic photosensory organs. The retinas of the stalk eye consist of two morphologically distinct visual cells, namely, the type I cells equipped with well-developed microvilli and the type II cells with less developed microvilli. The extracephalic photosensors comprise the dorsal eye, dermal photoreceptor, and brain photosensitive neurons. The characteristics of these cephalic and extracephalic photosensory organs have been studied from morphological and electrophysiological perspectives. However, little is known about the visual pigment molecules responsible for light detection in these organs. In the present study, we searched for opsin molecules that are expressed in the neural tissues of Onchidium and identified six putative signaling-competent opsin species, including Xenopsin1, Xenopsin2, Gq-coupled rhodopsin1, Gq-coupled rhodopsin2, Opsin-5B, and Gq-coupled rhodopsin-like. Immunohistochemical staining of four of the six opsins revealed that Xenopsin1, Gq-coupled rhodopsin1, and Gq-coupled rhodopsin2 are expressed in the rhabdomere of the stalk eye and in the dermal photoreceptor. Xenopsin2 was expressed in the type II photoreceptors of the stalk eye and in the ciliary photoreceptors of the dorsal eye. These immunohistochemical data were consistent with the results of the expression analysis, revealed by quantitative reverse transcription polymerase chain reaction. This study clarified the identities of opsins expressed in the extracephalic photosensory organs of Onchidium and the distinct molecular compositions among the photoreceptors.

Sniffing the human body volatile hexadecanal blocks aggression in men but triggers aggression in women.

In terrestrial mammals, body volatiles can effectively trigger or block conspecific aggression. Here, we tested whether hexadecanal (HEX), a human body volatile implicated as a mammalian-wide social chemosignal, affects human aggression. Using validated behavioral paradigms, we observed a marked dissociation: Sniffing HEX blocked aggression in men but triggered aggression in women. Next, using functional brain imaging, we uncovered a pattern of brain activity mirroring behavior: In both men and women, HEX increased activity in the left angular gyrus, an area implicated in perception of social cues. HEX then modulated functional connectivity between the angular gyrus and a brain network implicated in social appraisal (temporal pole) and aggressive execution (amygdala and orbitofrontal cortex) in a sex-dependent manner consistent with behavior: increasing connectivity in men but decreasing connectivity in women. These findings implicate sex-specific social chemosignaling at the mechanistic heart of human aggressive behavior.

Antenna Cleaning Is Essential for Precise Behavioral Response to Alarm Pheromone and Nestmate-Non-Nestmate Discrimination in Japanese Carpenter Ants (Camponotus japonicus).

Self-grooming of the antennae is frequently observed in ants. This antennal maintenance behavior is presumed to be essential for effective chemical communication but, to our knowledge, this has not yet been well studied. When we removed the antenna-cleaning apparatuses of the Japanese carpenter ant (C. japonicus) to limit the self-grooming of the antennae, the worker ants demonstrated the self-grooming gesture as usual, but the antennal surface could not be sufficiently cleaned. By using scanning electron microscopy with NanoSuit, we observed the ants' antennae for up to 48 h and found that the antennal surfaces gradually became covered with self-secreted surface material. Concurrently, the self-grooming-limited workers gradually lost their behavioral responsiveness to undecane-the alarm pheromone. Indeed, their locomotive response to the alarm pheromone diminished for up to 24 h after the antenna cleaner removal operation. In addition, the self-grooming-limited workers exhibited less frequent aggressive behavior toward non-nestmate workers, and 36 h after the operation, approximately half of the encountered non-nestmate workers were accepted as nestmates. These results suggest that the antennal sensing system is affected by excess surface material; hence, their proper function is prevented until they are cleaned.

Visualization of antennal lobe glomeruli activated by nonappetitive D-limonene and appetitive 1-octen-3-ol odors via two types of olfactory organs in the blowfly Phormia regina.

Appetite or feeding motivation relies significantly on food odors. In the blowfly Phormia regina, feeding motivation for sucrose is decreased by the odor of D-limonene but increased by the odor of 1-octen-3-ol odor. These flies have antennal lobes (ALs) consisting of several tens of glomerular pairs as a primary olfactory center in the brain. Odor information from different olfactory organs-specifically, the antennae and maxillary palps-goes to the corresponding glomeruli. To investigate how odors differently affect feeding motivation, we identified the olfactory organs and glomeruli that are activated by nonappetitive and appetitive odors. We first constructed a glomerular map of the antennal lobe in P. regina. Anterograde fluorescence labeling of antennal and maxillary afferent nerves, both of which project into the contralateral and ipsilateral ALs, revealed differential staining in glomerular regions. Some of the axonal fiber bundles from the antennae and maxillary palps projected to the subesophageal ganglion (SOG). We visualized the activation of the glomeruli in response to odor stimuli by immunostaining phosphorylated extracellular signal-regulated kinase (pERK). We observed different glomerulus activation under different odor stimulations. Referring to our glomerular map, we determined that antennal exposure to D-limonene odor activated the DA13 glomeruli, while exposure of the maxillary palps to 1-octen-3-ol activated the MxB1 glomeruli. Our results indicated that a nonappetitive odor input from the antennae and an appetitive odor input from the maxillary palps activate different glomeruli in the different regions of ALs in the blowfly P. regina. Collectively, our findings suggest that compartmentalization of glomeruli in AL is essential for proper transmission of odor information.

Characterization of Localization, Ligand Binding, and pH-Dependent Conformational Changes of Two Chemosensory Proteins Expressed in the Antennae of the Japanese Carpenter Ant, Camponotus Japonicus.

Camponotus japonicus uses basiconic antennal sensilla (s. basiconica) to sense a colony-specific blend of species-specific cuticular hydrocarbons (CHCs). The inner portion of the s. basiconica is filled with sensillar lymph and chemosensory proteins (CSPs) presumed to transport CHCs to olfactory neuron receptors. Although 12 CSPs have been found in C. japonicus antennae, we focused on CjapCSP1 and CjapCSP13. The molecular basis of CSP1 function was explored by observation of its structure in solution at pH 4.0 and 7.0 through circular dichroism (CD) and X-ray solution scattering. Although the secondary structure did not vary with pH change, the radius of gyration (Rg) was larger by 5.3% (0.74 Å increase) at pH 4.0 than at pH 7.0. The dissociation constant (Kd) for CjapCSP1 measured with a fluorescent probe, 1-N-phenylnaphthylamine, was larger at pH 4.0 than at pH 7.0, suggesting that acidic pH triggers ligand dissociation. In contrast to CjapCSP1, the Rg of CjapCSP13 was slightly smaller at pH 4.0 than at pH 7.0. Western blotting and immunohistochemistry with protein-specific antisera revealed that both CjapCSP1 and CjapCSP13 are detected in the antennae, but differ in their specific internal localization. Binding to four compounds, including the ant CHC (z)-9-tricosene, was examined. Although both CjapCSP1 and CjapCSP13 bound to (z)-9-tricosene, CjapCSP13 bound with higher affinity than CjapCSP1 and showed different binding properties. CjapCSP1 and CjapCSP13 are synthesized by the same cells of the antenna, but function differently in CHC distribution due to differences in their localization and binding characteristics.

Rac-Dependent Signaling from Keratinocytes Promotes Differentiation of Intradermal White Adipocytes.

Rac signaling affects numerous downstream targets in vitro; however, few studies have established in vivo levels. We generated mice with a single knockout (KO) of Rac1 (Keratin5(K5)-Cre;Rac1flox/flox, Rac1-KO) and double KO of Rac1 and Rac3 (K5-Cre;Rac1flox/flox;Rac3-/-, Rac1/Rac3-DKO) in keratinocytes. The hairless phenotype in Rac1-KO mice was markedly exacerbated in Rac1/Rac3-DKO mice. Strikingly, Rac1-KO mice exhibited thinner dermal white adipose tissue, which was considerably further reduced in Rac1/Rac3-DKO mice. DNA microarray using primary keratinocytes from Rac1/Rac3-DKO mice exhibited decreased mRNA levels of Bmp2, Bmp5, Fgf20, Fgf21, Fgfbp1, and Pdgfα. Combinational treatment with bone morphogenetic protein (BMP) 2 and fibroblast growth factor (FGF) 21 in culture medium, but not individual purified recombinant proteins, could differentiate 3T3-L1 fibroblasts into adipocytes, as could culture media from primary keratinocytes. Conversely, addition of anti-BMP2 or anti-FGF21 antibodies into the culture medium inhibited fibroblast differentiation. In addition, BMP2 and FGF21 treatment promoted adipocyte differentiation only of rat primary white adipocyte precursors but not rat primary brown adipocyte precursors. Furthermore, BMP2 and FGF21 treatment enhanced adipogenesis of normal human dermal fibroblasts. Notably, brown adipogenesis promoted by FGF21 was inhibited by BMP2. Thus, we propose a complex paracrine pathway from keratinocytes to intradermal pre-adipocytes, which functions as a Rac-dependent modulator of both white and brown adipogenesis.

Sampling, identification and sensory evaluation of odors of a newborn baby's head and amniotic fluid.

For baby odor analyses, noninvasive, stress-free sample collection is important. Using a simple method, we succeeded in obtaining fresh odors from the head of five newborn babies. These odors were chemically analyzed by two-dimensional gas chromatography coupled with mass spectrometry (GC × GC-MS), and compared with each other or with the odor of amniotic fluid from the baby's mother. We identified 31 chemical components of the volatile odors from neonate heads and 21 from amniotic fluid. Although 15 of these components were common to both sources, there was an apparent difference in the GC × GC patterns between the head and amniotic fluid odors, so the neonate head odor might be individually distinct immediately after birth. Therefore, we made artificial mixtures of the major odor components of the neonate head and maternal amniotic fluid, and used psychological tests to examine whether or not these odors could be distinguished from each other. Our data show that the artificial odor of a neonate head could be distinguished from that of amniotic fluid, and that the odors of artificial head odor mixtures could be correctly discriminated for neonates within an hour after birth and at 2 or 3 days of age.

Putative Neural Network Within an Olfactory Sensory Unit for Nestmate and Non-nestmate Discrimination in the Japanese Carpenter Ant: The Ultra-structures and Mathematical Simulation.

Ants are known to use a colony-specific blend of cuticular hydrocarbons (CHCs) as a pheromone to discriminate between nestmates and non-nestmates and the CHCs were sensed in the basiconic type of antennal sensilla (S. basiconica). To investigate the functional design of this type of antennal sensilla, we observed the ultra-structures at 2D and 3D in the Japanese carpenter ant, Camponotus japonicus, using a serial block-face scanning electron microscope (SBF-SEM), and conventional and high-voltage transmission electron microscopes. Based on the serial images of 352 cross sections of SBF-SEM, we reconstructed a 3D model of the sensillum revealing that each S. basiconica houses > 100 unbranched dendritic processes, which extend from the same number of olfactory receptor neurons (ORNs). The dendritic processes had characteristic beaded-structures and formed a twisted bundle within the sensillum. At the "beads," the cell membranes of the processes were closely adjacent in the interdigitated profiles, suggesting functional interactions via gap junctions (GJs). Immunohistochemistry with anti-innexin (invertebrate GJ protein) antisera revealed positive labeling in the antennae of C. japonicus. Innexin 3, one of the five antennal innexin subtypes, was detected as a dotted signal within the S. basiconica as a sensory organ for nestmate recognition. These morphological results suggest that ORNs form an electrical network via GJs between dendritic processes. We were unable to functionally certify the electric connections in an olfactory sensory unit comprising such multiple ORNs; however, with the aid of simulation of a mathematical model, we examined the putative function of this novel chemosensory information network, which possibly contributes to the distinct discrimination of colony-specific blends of CHCs or other odor detection.

A Novel Rac1-GSPT1 Signaling Pathway Controls Astrogliosis Following Central Nervous System Injury.

Astrogliosis (i.e. glial scar), which is comprised primarily of proliferated astrocytes at the lesion site and migrated astrocytes from neighboring regions, is one of the key reactions in determining outcomes after CNS injury. In an effort to identify potential molecules/pathways that regulate astrogliosis, we sought to determine whether Rac/Rac-mediated signaling in astrocytes represents a novel candidate for therapeutic intervention following CNS injury. For these studies, we generated mice with Rac1 deletion under the control of the GFAP (glial fibrillary acidic protein) promoter (GFAP-Cre;Rac1flox/flox). GFAP-Cre;Rac1flox/flox (Rac1-KO) mice exhibited better recovery after spinal cord injury and exhibited reduced astrogliosis at the lesion site relative to control. Reduced astrogliosis was also observed in Rac1-KO mice following microbeam irradiation-induced injury. Moreover, knockdown (KD) or KO of Rac1 in astrocytes (LN229 cells, primary astrocytes, or primary astrocytes from Rac1-KO mice) led to delayed cell cycle progression and reduced cell migration. Rac1-KD or Rac1-KO astrocytes additionally had decreased levels of GSPT1 (G1 to S phase transition 1) expression and reduced responses of IL-1ß and GSPT1 to LPS treatment, indicating that IL-1ß and GSPT1 are downstream molecules of Rac1 associated with inflammatory condition. Furthermore, GSPT1-KD astrocytes had cell cycle delay, with no effect on cell migration. The cell cycle delay induced by Rac1-KD was rescued by overexpression of GSPT1. Based on these results, we propose that Rac1-GSPT1 represents a novel signaling axis in astrocytes that accelerates proliferation in response to inflammation, which is one important factor in the development of astrogliosis/glial scar following CNS injury.

Estrogen induces estrogen receptor alpha expression and hepatocyte proliferation in the livers of male mice.

Estrogens play pivotal roles in sexual development, growth, reproduction, and sex differentiation and have been implicated in a number of physiological processes in various tissues. Most of the effects of estrogens are mediated by the estrogen receptors alpha (ERα), beta (ERß), and G protein-coupled receptor 30 (GPR30). The liver is known to be a target tissue for estrogen signaling, but the physiological role of this signaling is not well characterized. Through analyses of an estradiol (E2)-treated hepatocyte cell line and mice, we showed that E2 signaling controls hepatocyte proliferation. Importantly, our data showed that the E2 signaling that is mediated through ERα is crucial for efficient liver regeneration after partial hepatectomy (PH). PH rapidly induced marked increases in circulating E2 and ERα transcripts in periportal hepatocytes, well before the onset of hepatocyte proliferation. Taken together, our results indicate that increased E2 is one of the initiating signals that trigger liver regeneration. We suggest that E2 treatment could be beneficial for stimulating liver regeneration in humans.

Involvement of SIK3 in glucose and lipid homeostasis in mice.

Salt-inducible kinase 3 (SIK3), an AMP-activated protein kinase-related kinase, is induced in the murine liver after the consumption of a diet rich in fat, sucrose, and cholesterol. To examine whether SIK3 can modulate glucose and lipid metabolism in the liver, we analyzed phenotypes of SIK3-deficent mice. Sik3(-/-) mice have a malnourished the phenotype (i.e., lipodystrophy, hypolipidemia, hypoglycemia, and hyper-insulin sensitivity) accompanied by cholestasis and cholelithiasis. The hypoglycemic and hyper-insulin-sensitive phenotypes may be due to reduced energy storage, which is represented by the low expression levels of mRNA for components of the fatty acid synthesis pathways in the liver. The biliary disorders in Sik3(-/-) mice are associated with the dysregulation of gene expression programs that respond to nutritional stresses and are probably regulated by nuclear receptors. Retinoic acid plays a role in cholesterol and bile acid homeostasis, wheras ALDH1a which produces retinoic acid, is expressed at low levels in Sik3(-/-) mice. Lipid metabolism disorders in Sik3(-/-) mice are ameliorated by the treatment with 9-cis-retinoic acid. In conclusion, SIK3 is a novel energy regulator that modulates cholesterol and bile acid metabolism by coupling with retinoid metabolism, and may alter the size of energy storage in mice.

SIK3 is essential for chondrocyte hypertrophy during skeletal development in mice.

Chondrocyte hypertrophy is crucial for endochondral ossification, but the mechanism underlying this process is not fully understood. We report that salt-inducible kinase 3 (SIK3) deficiency causes severe inhibition of chondrocyte hypertrophy in mice. SIK3-deficient mice showed dwarfism as they aged, whereas body size was unaffected during embryogenesis. Anatomical and histological analyses revealed marked expansion of the growth plate and articular cartilage regions in the limbs, accumulation of chondrocytes in the sternum, ribs and spine, and impaired skull bone formation in SIK3-deficient mice. The primary phenotype in the skeletal tissue of SIK3-deficient mice was in the humerus at E14.5, where chondrocyte hypertrophy was markedly delayed. Chondrocyte hypertrophy was severely blocked until E18.5, and the proliferative chondrocytes occupied the inside of the humerus. Consistent with impaired chondrocyte hypertrophy in SIK3-deficient mice, native SIK3 expression was detected in the cytoplasm of prehypertrophic and hypertrophic chondrocytes in developing bones in embryos and in the growth plates in postnatal mice. HDAC4, a crucial repressor of chondrocyte hypertrophy, remained in the nuclei in SIK3-deficient chondrocytes, but was localized in the cytoplasm in wild-type hypertrophic chondrocytes. Molecular and cellular analyses demonstrated that SIK3 was required for anchoring HDAC4 in the cytoplasm, thereby releasing MEF2C, a crucial facilitator of chondrocyte hypertrophy, from suppression by HDAC4 in nuclei. Chondrocyte-specific overexpression of SIK3 induced closure of growth plates in adulthood, and the SIK3-deficient cartilage phenotype was rescued by transgenic SIK3 expression in the humerus. These results demonstrate an essential role for SIK3 in facilitating chondrocyte hypertrophy during skeletogenesis and growth plate maintenance.

A potent inhibitor of SIK2, 3, 3', 7-trihydroxy-4'-methoxyflavon (4'-O-methylfisetin), promotes melanogenesis in B16F10 melanoma cells.

Flavonoids, which are plant polyphenols, are now widely used in supplements and cosmetics. Here, we report that 4'-methylflavonoids are potent inducers of melanogenesis in B16F10 melanoma cells and in mice. We recently identified salt inducible kinase 2 (SIK2) as an inhibitor of melanogenesis via the suppression of the cAMP-response element binding protein (CREB)-specific coactivator 1 (TORC1). Using an in vitro kinase assay targeting SIK2, we identified fisetin as a candidate inhibitor, possibly being capable of promoting melanogenesis. However, fisetin neither inhibited the CREB-inhibitory activity of SIK2 nor promoted melanogenesis in B16F10 melanoma cells. Conversely, mono-methyl-flavonoids, such as diosmetin (4'-O-metlylluteolin), efficiently inhibited SIK2 and promoted melanogenesis in this cell line. The cAMP-CREB system is impaired in A(y)/a mice and these mice have yellow hair as a result of pheomelanogenesis, while Sik2(+/-); A(y)/a mice also have yellow hair, but activate eumelanogenesis when they are exposed to CREB stimulators. Feeding Sik2(+/-); A(y)/a mice with diets supplemented with fisetin resulted in their hair color changing to brown, and metabolite analysis suggested the presence of mono-methylfisetin in their feces. Thus, we decided to synthesize 4'-O-methylfisetin (4'MF) and found that 4'MF strongly induced melanogenesis in B16F10 melanoma cells, which was accompanied by the nuclear translocation of TORC1, and the 4'-O-methylfisetin-induced melanogenic programs were inhibited by the overexpression of dominant negative TORC1. In conclusion, compounds that modulate SIK2 cascades are helpful to regulate melanogenesis via TORC1 without affecting cAMP levels, and the combined analysis of Sik2(+/-) mice and metabolites from these mice is an effective strategy to identify beneficial compounds to regulate CREB activity in vivo.

Characterization of S100A11, a suppressive factor of fertilization, in the mouse female reproductive tract.

We recently found that Xenopus dicalcin, present in the extracellular egg-coating envelope, suppresses the efficiency of fertilization in vitro through binding to envelope-constituent glycoproteins. In the present study, we explored the mouse counterpart of Xenopus dicalcin, specifically its localization in the female reproductive tract and its action on mouse fertilization. Our homology and phylogenetic analyses using known S100 proteins showed that S100A11 is most closely related to Xenopus dicalcin. S100A11 was localized in the cytosol of luteal cells, but not in the follicle, in the mouse ovary, and also in the cytosol of the oviductal epithelial cells. In addition, our quantitative analyses revealed preferential expression of S100A11 in the ampullary region of the oviduct and at the estrus stage during the mouse estrous cycle. In the cumulus cell-oocyte complex dissected from the oviduct following ovulation, S100A11 was present in the plasma membrane of cumulus cells, but not in the zona pellucida, which is comparable with Ca(2+) -dependent binding of exogenously applied S100A11 to the plasma membrane of cumulus cells. Pretreatment of the cumulus cell-oocyte complex with recombinant S100A11 substantially reduced the efficiency of in vitro fertilization, but S100A10, the next closest S100 protein to Xenopus dicalcin, had no effect. These results suggested that S100A11 is the mouse counterpart of Xenopus dicalcin, suppresses the fertilization process through its action on cumulus cells, and thereby plays a key role in fertilization success in the mouse.

SIK2 is a key regulator for neuronal survival after ischemia via TORC1-CREB.

The cAMP responsive element-binding protein (CREB) functions in a broad array of biological and pathophysiological processes. We found that salt-inducible kinase 2 (SIK2) was abundantly expressed in neurons and suppressed CREB-mediated gene expression after oxygen-glucose deprivation (OGD). OGD induced the degradation of SIK2 protein concomitantly with the dephosphorylation of the CREB-specific coactivator transducer of regulated CREB activity 1 (TORC1), resulting in the activation of CREB and its downstream gene targets. Ca(2+)/calmodulin-dependent protein kinase I/IV are capable of phosphorylating SIK2 at Thr484, resulting in SIK2 degradation in cortical neurons. Neuronal survival after OGD was significantly increased in neurons isolated from sik2(-/-) mice, and ischemic neuronal injury was significantly reduced in the brains of sik2(-)(/-) mice subjected to transient focal ischemia. These findings suggest that SIK2 plays critical roles in neuronal survival, is modulated by CaMK I/IV, and regulates CREB via TORC1.

Phosphorylation of the CREB-specific coactivator TORC2 at Ser(307) regulates its intracellular localization in COS-7 cells and in the mouse liver.

The CREB-specific coactivator TORC2 (also known as CRTC2) upregulates gluconeogenic gene expression in the liver. Salt-inducible kinase (SIK) family enzymes inactivate TORC2 through phosphorylation and localize it in the cytoplasm. Ser(171) and Ser(275) were found to be phosphorylated in pancreatic beta-cells. Calcineurin (Cn) is proposed as the Ser(275) phosphatase, because its inhibitor cyclosporin A (CsA) stabilizes phospho-Ser(275) and retains TORC2 in the cytoplasm. Because the regulation of dephosphorylation at Ser(171) has not been fully clarified, we performed experiments with a range of doses of okadaic acid (OA), an inhibitor of PP2A/PP1, and with overexpression of various phosphatases and found that PP1 functions as an activator for TORC2, whereas PP2A acts as an inhibitor. In further studies using TORC2 mutants, we detected a disassociation between the intracellular distribution and the transcription activity of TORC2. Additional mutant analyses suggested the presence of a third phosphorylation site, Ser(307). The Ser(307)-disrupted TORC2 was constitutively localized in the nucleus, but its coactivator activity was normally suppressed by SIK1 in COS-7 cells. CsA, but not OA, stabilized the phosphogroup at Ser(307), suggesting that differential dephosphorylation at Ser(171) and Ser(307) cooperatively regulate TORC2 activity and that the nuclear localization of TORC2 is insufficient to function as a coactivator. Because the COS-7 cell line may not possess signaling cascades for gluconeogenic programs, we next examined the importance of Ser(307) and Ser(171) for TORC2's function in mouse liver. Levels of phosphorylation at Ser(171) and Ser(307) changed in response to fasting or fed conditions and insulin resistance of the mouse liver, which were modified by treatment with CsA/OA and by overexpression of PP1/PP2A/Cn. These results suggest that multiple phosphorylation sites and their phosphatases may play important roles in regulating TORC2/CREB-mediated gluconeogenic programs in the liver.

Involvement of SIK2/TORC2 signaling cascade in the regulation of insulin-induced PGC-1alpha and UCP-1 gene expression in brown adipocytes.

Salt-inducible kinase 2 (SIK2) is expressed abundantly in adipose tissues and represses cAMP-response element-binding protein (CREB)-mediated gene expression by phosphorylating the coactivator transducer of regulated CREB activity (TORC2). Phosphorylation at Ser(587) of SIK2 diminishes its TORC2 phosphorylation activity. In 3T3-L1 white adipocytes, SIK2 downregulates lipogenic gene in response to nutritional stresses. To investigate the impact of SIK2 on the function of brown adipose tissue (BAT), we used T37i brown adipocytes, mice with diet-induced obesity, and SIK2 mutant (S587A) transgenic mice. When T37i adipocytes were treated with insulin, the levels of peroxisome proliferator-activated receptor-coactivator-1alpha (PGC-1alpha) and uncoupling protein-1 (UCP-1) mRNA were increased, and the induction was inhibited by overexpression of SIK2 (S587A) mutant or dominant-negative CREB. Insulin enhanced SIK2 phosphorylation at Ser(587), which was accompanied by decrease in phospho-TORC2. Similarly, the decrease in the level of SIK2 phosphorylation at Ser(587) was observed in the BAT of mice with diet-induced obesity, which was negatively correlated with TORC2 phosphorylation. To confirm the negative correlation between SIK2 phosphorylation at Ser(587) and TORC2 phosphorylation in BAT, SIK2 mutant (S587A) was overexpressed in adipose tissues by using the adipocyte fatty acid-binding protein 2 promoter. The expression of recombinant SIK2 (S587A) was restricted to BAT, and the levels of phospho-TORC2 were elevated in BAT of transgenic mice. Male transgenic mice developed high-fat diet-induced obesity, and their BAT expressed low levels of PGC-1alpha and UCP-1 mRNA, suggesting that SIK2-TORC2 cascade may be important for the regulation of PGC-1alpha and UCP-1 gene expression in insulin signaling in BAT.

S100-annexin complexes--biology of conditional association.

S100 proteins and annexins both constitute groups of Ca2+-binding proteins, each of which comprises more than 10 members. S100 proteins are small, dimeric, EF-hand-type Ca2+-binding proteins that exert both intracellular and extracellular functions. Within the cells, S100 proteins regulate various reactions, including phosphorylation, in response to changes in the intracellular Ca2+ concentration. Although S100 proteins are known to be associated with many diseases, exact pathological contributions have not been proven in detail. Annexins are non-EF-hand-type Ca2+-binding proteins that exhibit Ca2+-dependent binding to phospholipids and membranes in various tissues. Annexins bring different membranes into proximity and assist them to fuse, and therefore are believed to play a role in membrane trafficking and organization. Several S100 proteins and annexins are known to interact with each other in either a Ca2+-dependent or Ca2+-independent manner, and form complexes that exhibit biological activities. This review focuses on the interaction between S100 proteins and annexins, and the possible biological roles of these complexes. Recent studies have shown that S100-annexin complexes have a role in the differentiation of gonad cells and neurological disorders, such as depression. These complexes regulate the organization of membranes and vesicles, and thereby may participate in the appropriate disposition of membrane-associated proteins, including ion channels and/or receptors.

Comprehensive interaction of dicalcin with annexins in frog olfactory and respiratory cilia.

Dicalcin (renamed from p26olf) is a dimer form of S100 proteins found in frog olfactory epithelium. S100 proteins form a group of EF-hand Ca(2+)-binding proteins, and are known to interact with many kinds of target protein to modify their activities. To determine the role of dicalcin in the olfactory epithelium, we identified its binding proteins. Several proteins in frog olfactory epithelium were found to bind to dicalcin in a Ca(2+)-dependent manner. Among them, 38 kDa and 35 kDa proteins were most abundant. Our analysis showed that these were a mixture of annexin A1, annexin A2 and annexin A5. Immunohistochemical analysis showed that dicalcin and all of these three subtypes of annexin colocalize in the olfactory cilia. Dicalcin was found to be present in a quantity almost sufficient to bind all of these annexins. Colocalization of dicalcin and the three subtypes of annexin was also observed in the frog respiratory cilia. Dicalcin facilitated Ca(2+)-dependent liposome aggregation caused by annexin A1 or annexin A2, and this facilitation was additive when both annexin A1 and annexin A2 were present. In this facilitation effect, the effective Ca(2+) concentrations were different between annexin A1 and annexin A2, and therefore the dicalcin-annexin system in frog olfactory and respiratory cilia can cover a wide range of Ca(2+) concentrations. These results suggested that this system is associated with abnormal increases in the Ca(2+) concentration in the olfactory and other motile cilia.