Cysteine string proteins: a potential link between synaptic vesicles and presynaptic Ca2+ channels.

Presynaptic calcium channels are key regulators of neurotransmitter release. Oocyte expression studies suggest that cysteine string proteins are essential subunits or modulators of these channels. Subcellular fractionation revealed that cysteine string proteins copurify with synaptic vesicles. An average vesicle had eight protein monomers with both the amino and carboxyl termini detected on the cytoplasmic face. Thus, docked synaptic vesicles may regulate presynaptic calcium channels and neurotransmitter release.

Expression and distribution of notch protein members in human placenta throughout pregnancy.

Notch signaling is an evolutionarily conserved mechanism used by invertebrates and vertebrates to control cell fates through close-range cell interactions. Four Notch receptors have been identified in vertebrates and different ligands, divided into Delta-like and Serrate-like (Jagged). Several studies have demonstrated that Notch signaling is involved in different branches of the cell fate decision tree: differentiation, proliferation and apoptosis. These three processes are finely regulated in human placenta in order to allow a successful pregnancy and a correct fetal growth. Moreover, Notch and its ligands participate in the vascular remodelling and stabilization, other two processes much important and ticklish in human placenta. So, we decided to investigate the pattern of expression of Notch-1, Notch-4 and Jagged-1, together with two members related to Notch pathway and involved in angiogenesis: VEGF and p21, in human placenta during gestation by immunoblotting and immunohistochemistry. We showed a modulation of Notch proteins throughout the pregnancy; in particular we showed a slight decrease of Notch-1 throughout pregnancy, with a decreased cytoplasmic staining from the first to the third trimester of gestation in cytotrophoblast and syncytiotrophoblast. In contrast Jagged-1 showed an increase throughout pregnancy especially in syncytiotrophoblast and stroma during the third trimester of gestation. In addition, we found by immunoblotting an increase of VEGF expression from the first to the third trimester and an intense VEGF expression inside endothelial cells throughout the gestation as also confirmed by immunohistochemistry. We also showed a decrease of p21 expression during the pregnancy both through immunoblotting and immunohistochemistry assays. Moreover, we observed Notch localization in extravillous trophoblast cells that are able to invade the decidualized endometrium. Our results suggest an involvement of Notch signaling in regulation of placental cell fate decision and in angiogenesis that are dramatically important to maintain a normal physiology of this organ during pregnancy.

[A fetal soft marker in obstetric ultrasonography: single umbilical artery]. / Un fetal soft marker nell' ultrasonografia ostetrica: l'arteria ombelicale unica.

The recent advancement in the field of ultrasonography allows for the prenatal precocious diagnosis of an ever increasing number of congenital defects found in various areas of the foetal body. These phenotype variants (markers) and/or morphological anomalies reveal in the majority of cases of a foetus with chromosome defects. They represent ''alarm bells'' that intrigue us to uncover any average case with more tests. It is for this that many more efforts are made to identify echographical markers which allow us to select among the pregnant women those that are not at risk and to advise those that may be of the existence of a specific cytogenetic test. One of these markers is actually represented by the single umbilical artery. This anomaly is made up of the presence of only two vessels (an artery and a vein) at the level of the umbilical cord, and its lack of an artery. The clinical meaning of this pathology is not yet completely known today. Often, in fact, when isolated, it is not associated with a chromosome defect and to other foetal pathologies. When, however, it is presented as associated to other soft markers or other structural anomalies, the risk of a chromosome defect is notably higher.

A Xenopus cysteine string protein with a cysteine residue in the J domain.

A cDNA clone encoding a Xenopus cysteine string protein (Xcsp) was isolated and sequenced. The deduced primary sequence of Xcsp is very similar to other vertebrate csps with the exception of a cysteine residue that lies outside of the cysteine-string domain. This cysteine residue replaces a serine that is highly conserved among vertebrate csps, and thus may be of functional importance. Xcsp mRNA appears as a 4.6 kb species on Northern analysis, and immunoblot of Xenopus brain membranes reveals a single, 35 kDa Xcsp that can be deacylated, like other csps.

Intrinsic membrane association of Drosophila cysteine string proteins.

Cysteine string proteins (csps) are highly conserved constituents of vertebrate and invertebrate secretory organelles. Biochemical and immunoprecipitation experiments implied that vertebrate csps were integral membrane proteins that were tethered to the outer leaflet of secretory vesicles via the fatty acyl residues of their extensively acylated cysteine string. Independently, work of others suggested that Drosophila csps were peripheral membrane proteins that were anchored to membranes by a mechanism that was independent of the cysteine string and its fatty acyl residues. We extended these investigation and found first that sodium carbonate treatment partially stripped both csps and the integral membrane protein, synaptotagmin, from Drosophila membranes. Concomitantly, carbonate released fatty acids into the medium, arguing that it has a mild, solubilizing effect on these membranes. Second, we observed that Drosophila csps behaved like integral membrane proteins in Triton X-114 partitioning experiments. Third, we found that when membrane-bound csps were deacylated, they remained membrane bound. Moreover, it appeared that hydrophobic interactions were necessary for this persistent membrane association of csps. Thus, neither reducing conditions, urea, nor chaotropic agents displaced deacylated csps from membranes. Only detergents were effective in solubilizing deacylated csps. Finally, by virtue of the inaccessibility of deacylated csps to thiol alkylation by the membrane-impermeant alkylating reagent, iodoacetic acid, we inferred that it was the cysteine string domain that mediated the membrane association of deacylated csps. Thus, we conclude that under physiological conditions csps are integral membrane proteins of secretory organelles, and that the cysteine string domain plays a vital role in the membrane association of these proteins.

Electrical and optical monitoring of alpha-latrotoxin action at Drosophila neuromuscular junctions.

Electrophysiological recording demonstrates that alpha-latrotoxin, a 125,000 mol. wt component of black widow spider venom, promotes high frequency quantal discharges at larval neuromuscular junctions of Drosophila. Concomitantly, fluorescence imaging of presynaptic calcium ion activity reveals that this toxin qualitatively elevates cytosolic ionized calcium in this preparation. These activities of alpha-latrotoxin are selectively antagonized by a monoclonal antibody, 4C4.1, that was previously shown to inhibit the action of this toxin in PC-12 cells. However, 4C4.1 does not block the release-promoting activity of gel-filtered extracts of black widow spider venom. This indicates that black widow spider venom has multiple components that promote quantal transmitter secretion in invertebrates. This investigation demonstrates that alpha-latrotoxin is among the active principles in black widow spider venom that enhance transmitter release and raise cytosolic ionized calcium in Drosophila. These results suggest that Drosophila, because of the relative ease of genetic manipulation, may be useful to study the target protein(s) that mediate the binding and action of alpha-latrotoxin at nerve endings. Moreover, the procedure that we report for loading Drosophila nerve terminals with the calcium ion-sensing dye, Calcium Crimson, may have utility for studying calcium dynamics in mutant alleles with alterations in synapse development and function in this organism.

The nucleotide and deduced amino acid sequence of a rat cysteine string protein.

Cysteine string proteins are novel, heavily lipidated components of synaptic vesicles. They have previously been studied in Drosophila (insect) and Torpedo (fish). To facilitate further investigation of the structure and function of these proteins in mammals, we isolated and sequenced the cDNA and conducted an initial characterization of a rat cysteine string protein. Nucleotide sequencing reveals that this rat protein is highly homologous to the insect and fish cysteine string proteins. At the amino acid level, the fish and rat proteins are 82% identical. The rat cysteine string protein is encoded by an approximately 5 kb mRNA that is ubiquitously expressed in rat brain. Using antibodies that cross-react with the rat protein, we find that the rat cysteine string protein is predominantly associated with nerve endings and synaptic vesicles. Moreover, like its Torpedo (fish) counterpart, it is extensively fatty acylated. It will be of considerable interest to ascertain the functional correlates of these cross-species similarities of cysteine string proteins.

Cysteine string proteins and presynaptic function.

A brief review is presented of investigations of a novel family of synaptic vesicle proteins, the cysteine string proteins (csps). Studies of csp mutants in Drosophila reveal that csps are crucial components of the excitation-secretion machinery at nerve terminals. Current data cannot distinguish between a primary role of csps in modulating calcium ion influx at the nerve terminal versus a more-direct role in the exocytotic cascade. In this context, the remarkable post-translational modification of csps, namely the fatty acylation of as many as 12 of the 13 cysteine residues of the Torpedo protein, suggests that csps may participate more directly in the process of membrane fusion that underlies exocytosis. This would be achieved by using the fatty acyl chains of the csps as templates for 'lipid flow' that would allow the fusion of vesicular and plasma membranes. These hypotheses provide a useful framework for empirical tests of the role of csps in nerve terminal function.

Cysteine-string proteins: a cycle of acylation and deacylation?

We used tunicamycin, an inhibitor of protein fatty acylation, to examine the possibility that there is a cycle of acylation and deacylation of cysteine string proteins at nerve terminals. Using both physiological and immunoblot approaches, we obtained no evidence for a cycle of acylation and deacylation that affects these proteins. These data suggest that this lipid modification of cysteine string proteins is relatively more stable than that observed for other nerve ending proteins, like SNAP-25.

Evaluation of a dual-sorbent trap for monitoring organic compounds in air.

The performance of a new kind of multi-sorbent trap for use in the simultaneous determination of compounds of different volatility and polarity was investigated. The adsorbents employed for this purpose were Carbograph 2 and Carbograph 5. The performance of this trap was evaluated in terms of thermal desorption and solvent extraction recoveries of substances belonging to the main classes of organic compounds, at different amounts and volumes of air sampled corresponding to concentrations ranging from 0.1 to 1000 mg/m3. The tubes examined allowed the trapping of the compounds used and their complete desorption with the procedure best suited to the analytical problem.

Modulation of apelin and APJ receptor in normal and preeclampsia-complicated placentas.

Apelin is an endogenous ligand of the human orphan receptor APJ. This peptide is produced through processing from the C-terminal portion in the pre-pro-protein consisting of 77 amino acid residues and exists in multiple molecular forms. Although the main physiological functions of apelin have not yet been clarified, it is known that apelin is involved in the regulation of blood pressure, blood flow and central control of body fluid homeostasis in different organs. Since human placenta is a tissue where vasculogenesis, blood pressure and flow are dramatically important to allow a normal embryonic and fetal growth and development, the aim of the present study was to investigate the immunohistochemical distribution of apelin and APJ in normal placentas throughout pregnancy and in preeclampsia-complicated placentas. Specifically, we observed that in normal placentas the expression levels of apelin decreased from the first to the third trimester of gestation in both cytotrophoblast and syncytiotrophoblast cells and in the stroma of placental villi, in contrast with increased expression levels of APJ in the cytoplasm of cytotrophoblast cells and in the cytoplasm of endothelial cells of normal placenta samples. In contrast, in preeclampsia-complicated pregnancies, we observed a very strong increase of expression levels of both apelin and APJ receptor in all the placental compartments, cytotrophoblast, syncytiotrophoblast and stroma with a particular increase in endothelial cells inside preeclamptic placental villi. Our data seem to indicate an important role of apelin and APJ in the regulation of fetal development through a correct regulation of human placenta formation during pregnancy. Moreover, the strong expression levels of apelin and APJ in preeclamptic placentas, suggest their possible involvement in the onset of this pathology.

Antidesmoplakin antibodies in pemphigus vulgaris.

BACKGROUND: Besides being present in paraneoplastic pemphigus (PNP), circulating antidesmoplakin (DP) antibodies have been found anecdotally in other bullous diseases, including pemphigus foliaceus and pemphigus vulgaris. OBJECTIVES: To verify how frequent anti-DP antibodies are in pemphigus vulgaris. METHODS: We studied 48 sera from patients with proven pemphigus vulgaris (29 mucosal dominant pemphigus and 19 mucocutaneous pemphigus) by indirect immunofluorescence (IIF) with rat bladder epithelium (RBE) as a substrate and by immunoblotting (IB) on human keratinocyte cultures enriched in DP. RESULTS: Ten sera (21%) were positive in IIF on RBE. By IB, eight sera proved to have antibodies to both DP I (250 kDa) and DP II (210 kDa), one serum had antibodies directed to DP I only, and two sera to DP II only. CONCLUSIONS: Our data confirm that RBE is not a specific IIF substrate for the serological diagnosis of PNP. It remains a sensitive and specific substrate for the detection of anti-DP antibodies, which, in patients with pemphigus vulgaris, are probably caused by an epitope-spreading phenomenon.

Ocular 'non-scarring' mucous membrane pemphigoid associated with anti-laminin-5 antibodies.

Mucous membrane pemphigoid is a rare, chronic autoimmune disease characterized by subepidermal blistering and scarring, predominantly affecting mucous membranes. Ocular involvement frequently occurs and often represents the only manifestation of the disease. We describe a 62-year-old woman with a bilateral 18-month duration of conjunctival hyperaemia, associated with erythema and oedema of the eyelids, lacking any typical ocular signs of mucous membrane pemphigoid such as sub-conjuctival fibrosis and scarring. Histology was not significant. Direct immunofluorescence of the conjunctiva showed IgG, IgA and complement deposition along the basement membrane zone. Immunoprecipitation analysis of affinity purified laminin-5 revealed a band consistent with the beta3 chain of laminin-5. This represents the first case of pure ocular mucous membrane pemphigoid associated with anti-laminin-5 antibodies.

Alpha-latrotoxin: preparation and effects on calcium fluxes.

A toxin that causes a massive presynaptic activation of transmitter release from nerve terminals is alpha-latrotoxin, isolated from Latrodectus tredecimguttatus spider venom. This toxin has been highly purified, utilizing as a biological assay a toxin-dependent increase in 45Ca(2+)-accumulation by PC12 cells. The purification protocol includes an ion-exchange step and a gel-filtration column, by fast-flow liquid chromatography. The resulting toxin is a polypeptide of about 125 kDa in molecular mass. At nmol concentrations it specifically activates calcium influx and transmitter secretion after interacting with neuronal acceptors of the presynaptic membrane. The inhibitory effect of trivalent ions (which may develop as degradation product of 45Ca2+) on toxin-dependent calcium accumulation by PC12 cells is described. The results obtained suggest that calcium fluxes directly involved in the neurosecretory event, may occur through newly formed toxin-dependent channels.

Antipeptide antibodies against a Torpedo cysteine-string protein.

An antipeptide antiserum was raised against the C-terminal undecapeptide of a Torpedo cysteine-string protein (csp), a putative subunit or modulator of presynaptic calcium channels. This antiserum was shown to identify selectively the 27-kDa in vitro translation product of the csp cRNA both by immunoprecipitation and on immunoblots. When affinity-purified anti-csp antibodies were used to probe immunoblots of membrane proteins from Torpedo electric organ or liver, specific immunoreactivity was detected only in electric organ. This immunoreactivity was associated principally with a single protein species of about 34 kDa. These results indicate that csp immunoreactivity is detectably expressed in electroplax, a heavily innervated tissue, but not in liver, which should have an appreciably lower abundance of presynaptic calcium channel proteins. Moreover, the increased relative molecular mass of csp in electric organ (compared with in vitro translated material) implies that csp is posttranslationally modified. Finally, immunoblot analysis of either intact, alkali-treated, or solubilized membrane fractions of electric organ reveals that csp is predominantly a membrane protein.

Cysteine-string proteins as templates for membrane fusion: models of synaptic vesicle exocytosis.

Cysteine-string proteins are relatively small, cysteine-rich components of synaptic vesicle membranes. Recent investigations demonstrated that at least 11 of the 13 cysteine residues of the Torpedo cysteine-string protein are fatty acylated. This exceptional level of fatty acylation occurs along a short stretch (less than 25 residues) of amino acids which are flanked on either side by very polar amino and carboxy termini. This amphipathic structure may have unique capabilities to catalyze events at membrane interfaces. We propose two distinct pathways to explain how these capabilities might subserve membrane fusion and exocytosis.

The cloning of a cDNA encoding a protein (latrodectin) which co-purifies with the alpha-latrotoxin from the black widow spider Latrodectus tredecimguttatus (Theridiidae).

A cDNA encoding a polypeptide of 88 amino acids was cloned following the rapid amplification of cDNA ends (RACE) procedure using mRNA isolated from the venom glands of the Mediterranean black widow spider (Latrodectus tredecimguttatus) and oligonucleotides based on the sequence of a tryptic fragment putatively from alpha-latrotoxin. Apart from a potential signal peptide, the rest of this small protein, named latrodectin, was highly hydrophilic, having a calculated molecular mass of 7945 Da and a pI of 4.3. Northern-blot analysis showed that the mRNA was specifically expressed in the venom gland of L. tredecimguttatus and that it was well conserved between two geographically remote species (L. geometricus and L. indistinctus). A polyclonal serum raised in rabbits against the C-terminal sequence of latrodectin detected cross-reactive proteins in the venom fluid, venom gland extracts, and in purified alpha-latrotoxin, suggesting that latrodectin is intimately associated with alpha-latrotoxin. Finally, we produced a recombinant protein in a cell system infected with baculovirus and developed an immunoaffinity purification procedure for latrodectin to facilitate further structural and functional analyses of the molecule.

Extensive lipidation of a Torpedo cysteine string protein.

Cysteine string proteins are relatively low mass components of synaptic vesicle membranes. Structurally, their primary sequence is distinguished by a remarkable, cysteine-rich motif. Investigations revealed an unprecedented degree of lipidation of these cysteine residues. At least 11 of the 13 cysteines of the Torpedo protein were modified, principally by palmitoyl moieties. This fatty acylation creates a prominent hydrophobic domain flanked by polar amino and carboxyl termini. An amphipathic structure of this type is uniquely suited to mediate events at membrane interfaces. Thus, cysteine string proteins are candidates to participate in exocytotic membrane fusion.

Cysteine string protein immunoreactivity in the nervous system and adrenal gland of rat.

Cysteine string proteins (csps) are a recently discovered class of cysteine-rich proteins. They have been shown to associate preferentially with synaptic vesicle fractions of Torpedo electric organ or rat brain where they have been implicated in events associated with transmitter secretion. However, to date there has been no information concerning the distribution of csps in rat tissues. We investigated the localization of csps in the rat retina and CNS using immunohistochemistry with affinity purified anti-csp antibodies. Specific csp immunoreactivity having a punctate appearance is present throughout the neuraxis. Csp immunoreactivity is particularly abundant in synapse-rich regions including those of the retina, main olfactory bulb, hippocampal formation, and cerebellum. White matter tracts are devoid of csp immunoreactivity. Neuromuscular junctions show strong csp immunoreactivity. This localization of csp immunoreactivity is compatible with a role for csps in presynaptic events at a wide variety of synapses. Immunohistochemical analysis of a non-neuronal, secretory tissue, the adrenal gland, reveals prominent csp immunoreactivity in the chromaffin cells of the adrenal medulla. However, csp immunoreactivity is not detected in adrenal cortical regions. These findings are confirmed and extended by immunoblot and Northern analyses which identify a 35 kDa and a 5 kb product, respectively, in extracts of adrenal. The presence of csps in the adrenal medulla suggests that these proteins may also participate in secretion-related events in certain non-neuronal cells.

Cysteine string proteins are associated with cortical granules of Xenopus laevis oocytes.

Cysteine string proteins (csps) are associated with secretory organelles in a wide range of eukaryotic cells. Functional studies of these proteins indicate that they subserve one or more vital steps in the pathway of regulated exocytosis. Here, we document the presence of csps in fully grown (stage VI) oocytes of the frog, Xenopus laevis. Both Northern and immunoblot data support the conclusion that csps are expressed in these cells. In addition, immunoreactive csp is seen even at the earliest stage of oocyte development, namely, in stage I oocytes. Finally, immunoblot and immunocytochemical results indicate that csps are associated with cortical granules of stage II-VI oocytes. These observations suggest that csps participate in the cortical reaction that underlies the sustained block to polyspermy in Xenopus eggs. Moreover, because of the relative ease of manipulating cells as large as Xenopus oocytes, this system harbors considerable promise as a model for studying the role of csps and other proteins in exocytotic events.