Wingless (Wg) is a member of the Wnt family of growth factors, secreted proteins that control proliferation and differentiation during development. Studies in Drosophila have shown that responses to Wg require cell-surface heparan sulphate, a glycosaminoglycan component of proteoglycans. These findings suggest that a cell-surface proteoglycan is a component of a Wg/Wnt receptor complex. We demonstrate here that the protein encoded by the division abnormally delayed (dally) gene is a cell-surface, heparan-sulphate-modified proteoglycan. dally partial loss-of-function mutations compromise Wg-directed events, and disruption of dally function with RNA interference produces phenotypes comparable to those found with RNA interference of wg or frizzled (fz)/Dfz2. Ectopic expression of Dally potentiates Wg signalling without altering levels of Wg and can rescue a wg partial loss-of-function mutant. We also show that dally, a regulator of Decapentaplegic (Dpp) signalling during post-embryonic development, has tissue-specific effects on Wg and Dpp signalling. Dally can therefore differentially influence signalling mediated by two growth factors, and may form a regulatory component of both Wg and Dpp receptor complexes.

To study the molecular mechanisms underlying neuronal programmed cell death (PCD), we performed differential display screening for genes, the expression of which was induced during PCD in the sympathetic neuron culture model deprived of NGF. We cloned a gene encoding a novel polypeptide (DP5) which consisted of 92 amino acids. DP5 polypeptide had no homology with any other known protein and contained no motif that would indicate its putative biochemical functions. DP5 mRNA levels peaked at 15 h after nerve growth factor withdrawal, concurrent with the time at which neurons were committed to die. The induction of DP5 gene expression was blocked when cell death was rescued by treatment with cycloheximide, KCl, or the cyclic AMP analogue CPTcAMP. Overexpression of the full-length DP5 in cultured sympathetic neurons was in itself sufficient to induce apoptosis. These results suggest that DP5 plays a role in programmed neuronal death. Programmed cell death (PCD)1 is an indispensable phenomenon for proper development of the nervous system. Roughly half of all neurons produced by neurogenesis die during development of the mammalian nervous system (1). Neuronal survival is determined largely by neurotrophic factors such as NGF produced by target cells, and neurons that do not obtain an adequate supply of survival factors undergo apoptosis (2). Dissociated sympathetic neurons from rat superior cervical ganglia (SCG) are mainly used as an in vitro model of neuronal PCD and have been characterized extensively (3, 4). In this culture system, the majority of neurons die after removal of NGF from the culture medium. The characteristics of this neuronal death such as shrinkage of the neuronal soma with intact organelles, nuclear condensation, fragmentation of the DNA into oligonucleosomes, and blebbing of the plasma membrane are hallmarks of apoptosis (5, 6). Neuronal death in this system can be prevented by inhibitors of RNA or protein synthesis, suggesting that this phenomenon is controlled by a genetic program (7).In the search for constituents of the genetic program, several genes have been identified using this in vitro model. Immediate early genes such as c-fos and c-jun and cell cycle-related genes such as c-myb and cyclin D1 (8, 9) are these candidates. Especially cell cycle-related genes stimulate the postmitotic neurons to attempt re-entry into the cell cycle, and these comflicting growth-regulatory signals are thought to cause neurons to undergo apoptosis. On the other hand, several anti-apoptotic proteins such as Bcl-2 (10, 11), adenovirus E1B19k (12), or cowpox virus CrmA gene products (13) have been reported. Overexpression of the bcl-2 gene products in sympathetic neurons has been shown to protect neurons from apoptosis (10). Anti-apoptotic properties of Bcl-2 have been reported to prevent the loss of mitochondrial function (14). CrmA gene products also prevent neuronal death induced by NGF deprivation. This activity is attributed to interleukin 1␤-converting enzyme protease inhibition (13, 15).Re-entry into the...

Modulatory calcineurin-interacting proteins (MCIPs)--also termed regulators of calcineurin (RCNs), calcipressins, or DSCR1 (Down's syndrome critical region 1)--are highly conserved regulators of calcineurin, a Ca(2+)/calmodulin-dependent protein phosphatase . Although overexpression experiments in several organisms have revealed that MCIPs inhibit calcineurin activity , their in vivo functions remain unclear. Here, we show that the Drosophila MCIP sarah (sra) is essential for meiotic progression in oocytes. Eggs from sra null mothers are arrested at anaphase of meiosis I. This phenotype was due to loss of function of sra specifically in the female germline. Sra is physically associated with the catalytic subunit of calcineurin, and its overexpression suppresses the phenotypes caused by constitutively activated calcineurin, such as rough eye or loss of wing veins. Hyperactivation of calcineurin signaling in the germline cells resulted in a meiotic-arrest phenotype, which can also be suppressed by overexpression of Sra. All these results support the hypothesis that Sra regulates female meiosis by controlling calcineurin activity in the germline. To our knowledge, this is the first unambiguous demonstration that the regulation of calcineurin signaling by MCIPs plays a critical role in a defined biological process.

The Drosophila melanogaster sex-peptide (melSP) is a seminal fluid component that induces postmating responses (PMR) of females via the sex-peptide receptor (SPR) . Although SP orthologs are found in many Drosophila species, their functions remain poorly characterized. It is unknown whether SP functions are conserved across species or rather specific to each species. Here, we developed a GFP-tagged melSP (G-SP) and used it to visualize cross-species binding activity to the female reproductive system of various species. First we demonstrated that ectopically expressed G-SP induced PMR in D. melanogaster females and bound to the female reproductive system, most notably to the common oviduct. No binding occurred in the females lacking SPR, indicating that G-SP binding was dependent on SPR. Next we tested whether G-SP binds to the common oviducts from 11 Drosophila species using dissected reproductive tracts. The binding was observed in six species belonging to the D. melanogaster species group, but not to those outside the group. Injection of melSP reduced the receptivity of females belonging to the D. melanogaster species group, but not of those outside the group, being consistent with the ability to bind G-SP. Thus the SP-mediated PMR appears to be limited to this species group. SPR was expressed in the oviducts at high levels in this group; therefore, we speculate that an enhanced expression of SPR in the oviduct was critical to establish the SP-mediated PMR during evolution.KEYWORDS sex-peptide; SP receptor; GFP-tag; postmating response T HE mating behavior and physiology of Drosophila melanogaster females are dramatically modified after copulation: they reject courting males by extruding their ovipositor, a behavior not seen in virgin females and start to lay many eggs (Kubli 1992). Sex-peptide (SP), a seminal fluid peptide, has been shown to play a major role in eliciting postmating response (PMR). Injection of SP into the abdominal cavity of virgin females reduces receptivity and stimulates oviposition (Chen et al. 1988) and these phenotypes can be induced by ectopic expression of SP in virgin females (Aigaki et al. 1991). Furthermore, experiments involving an SP null mutant generated by gene targeting and dsRNAi-mediated gene knockdown unambiguously demonstrated that SP is a major component in inducing changes in receptivity, ovulation, and oviposition in mated females (Liu and Kubli 2003;Chapman et al. 2003). In addition, SP stimulates food intake (Hanin et al. 2011) and activates immune response genes (Peng et al. 2005b).An extensive transgenic RNAi screen identified a receptor for sex-peptide (SPR), a G-protein-coupled receptor broadly expressed in the female reproductive tracts and in some neural tissues (Yapici et al. 2008). Mutant females deleted for SPR do not respond to mating, accept repeated mating, and maintain a low level of oviposition (Yapici et al. 2008). It has been demonstrated that SPR expression in a limited number of pickpocket-expressing neurons in the female common oviduct was...

To elucidate the molecular mechanisms underlying neuronal death after transient forebrain ischemia, we cloned genes expressed after transient forebrain ischemia in the Mongolian gerbil by a differential display method. A gerbil homolog of rat zinc transporter, ZnT-1, which transports intracellular Zn 2ϩ out of cells, was isolated. Its expression became detectable exclusively in pyramidal neurons of the CA1 region 12 hr after ischemia and reached a maximum from day 1 to day 2 as shown by in situ hybridization. By day 7, expression had disappeared entirely from the cells in the CA1 region, because the neurons had died. No other brain regions exhibited such a significant level of ZnT-1 mRNA expression during this period. Zn 2ϩ was shown to accumulate in CA1 pyramidal neurons expressing ZnT-1 mRNA after the ischemia by using zinquin, a zinc-specific fluorescent dye. When primary hippocampal neurons were exposed to a high dose of Zn 2ϩ , ZnT-1 mRNA accumulated. These results suggest that the induction of ZnT-1 mRNA observed in CA1 neurons was caused by an increase in the intracellular Zn 2ϩ concentration. It was reported recently that Zn 2ϩ chelator blocked neuronal death after ischemia and that the influx of Zn 2ϩ might be a key mechanism underlying neuronal death. The induction of ZnT-1 mRNA in CA1 pyramidal neurons fated to die after transient ischemia is of interest to the study of postischemic events and the molecular mechanisms underlying delayed neuronal death.

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DP5, which contains a BH3 domain, was cloned as a neuronal apoptosis-inducing gene. To confirm that DP5 interacts with members of the Bcl-2 family, 293T cells were transiently co-transfected with DP5 and Bcl-xl cDNA constructs, and immunoprecipitation was carried out. The 30-kDa Bcl-xl was co-immunoprecipitated with Myc-tagged DP5, suggesting that DP5 physically interacts with Bcl-xl in mammalian cells. Previously, we reported that DP5 is induced during neuronal apoptosis in cultured sympathetic neurons. Here, we analyzed DP5 gene expression and the specific interaction of DP5 with Bcl-xl during neuronal death induced by amyloid-␤ protein (A ␤). DP5 mRNA was induced 6 h after treatment with A ␤ in cultured rat cortical neurons. The protein encoded by DP5 mRNA showed a specific interaction with Bcl-xl. Induction of DP5 gene expression was blocked by nifedipine, an inhibitor of L-type voltage-dependent calcium channels, and dantrolene, an inhibitor of calcium release from the endoplasmic reticulum. These results suggested that the induction of DP5 mRNA occurs downstream of the increase in cytosolic calcium concentration caused by A ␤. Moreover, DP5 specifically interacts with Bcl-xl during neuronal apoptosis following exposure to A ␤, and its binding could impair the survival-promoting activities of Bcl-xl. Thus, the induction of DP5 mRNA and the interaction of DP5 and Bcl-xl could play significant roles in neuronal degeneration following exposure to A ␤.Apoptosis, or programmed cell death, plays an important role not only in neuronal development and differentiation of the central nervous system but also in the pathogenesis of a variety of neurodegenerative disorders such as Alzheimer's disease. However, the molecular events or cascades underlying neuronal death regulated by the genetic program still remain unclear. Elucidation of the molecular mechanisms underlying neuronal death could contribute to understanding of the pathophysiology of neurodegenerative disorders such as Alzheimer's disease.Previously, we isolated a novel gene named DP5 that is induced during neuronal apoptosis using rat sympathetic neurons in culture deprived of NGF (1).1 This gene has the following unique features: 1) the encoded protein has a BH3 domain, which is essential for interaction with Bcl-2 and Bcl-xl, and a transmembrane region at its C-terminal; 2) its expression shows marked induction with peak levels at 15 h after NGF withdrawal, concurrent with the time at which neurons are committed to die in the sympathetic culture model; and 3) overexpression of full-length DP5 in cultured neurons was sufficient to induce apoptosis. In the developing murine nervous system, DP5 mRNA was localized in several tissues such as the trigeminal and dosal root ganglia and the anterior horn of the spinal cord, which are known to contain a number of apoptotic cells in the mouse embryo. These observations suggested that DP5 could be associated with the phenomena of neuronal death in vivo (2).Recently, Inohara et al. (3) cloned the human gene Harakiri ...

Imd-mediated innate immunity is activated in response to infection by Gram-negative bacteria and leads to the activation of Jun amino-terminal kinase (JNK) and Relish, a nuclear factor-jB transcription factor responsible for the expression of antimicrobial peptides. Plenty of SH3s (POSH) has been shown to function as a scaffold protein for JNK activation, leading to apoptosis in mammals. Here, we report that POSH controls Imd-mediated immunity signalling in Drosophila. In POSHdeficient flies, JNK activation and Relish induction were delayed and sustained, which indicated that POSH is required for properly timed activation and termination of the cascade. The RING finger of POSH, possessing ubiquitin-ligase activity, was essential for termination of JNK activation. We show that POSH binds to and degrades TAK1, a crucial activator of both the JNK and the Relish signalling pathways. These results establish a novel role for POSH in the Drosophila immune system.