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1.
Michael S. Lipkowitz Edgar Leal-Pinto B. Eleazar Cohen Ruth G. Abramson 《Glycoconjugate journal》2002,19(7-9):491-498
UAT, also designated galectin 9, is a multifunctional protein that can function as a urate channel/transporter, a regulator of thymocyte-epithelial cell interactions, a tumor antigen, an eosinophil chemotactic factor, and a mediator of apoptosis. We review the evidence that UAT is a transmembrane protein that transports urate, describe our molecular model for this protein, and discuss the evidence from epitope tag and lipid bilayer studies that support this model of the transporter. The properties of recombinant UAT are compared with those of urate transport into membrane vesicles derived from proximal tubule cells in rat kidney cortex. In addition, we review channel functions predicted by our molecular model that resulted in the novel finding that the urate channel activity is regulated by sugars and adenosine. Finally, the presence and possible functions of at least 4 isoforms of UAT and a closely related gene hUAT2 are discussed. Published in 2004. 相似文献
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The cellular interactions of laminin fragments. Cell adhesion correlates with two fragment-specific high affinity binding sites 总被引:26,自引:0,他引:26
M Aumailley V Nurcombe D Edgar M Paulsson R Timpl 《The Journal of biological chemistry》1987,262(24):11532-11538
The molecular interactions of laminin with several tumor cell lines and skin fibroblasts were investigated by radioligand binding studies and cell attachment assays using laminin, the laminin-nidogen complex, and laminin fragments as substrates and also domain-specific antibodies as inhibitors of cell attachment. The majority of cells showed a dual binding pattern for fragments 1 and 8 which originate from short-arm or long-arm structures of laminin, respectively. Both of these fragments in solution bind to suspended cells with high affinity (KD = 1-10 nM), with the receptor numbers for each fragment depending on the cell type. Competition studies and independent variation of receptor numbers demonstrated that the cell-binding structures on each fragment are different, implicating the existence of two distinct cellular receptors for laminin. The ability of these fragments to act as substrates for cell adhesion correlated with the presence of high affinity binding sites on the cells. However, only antibodies to fragment 8 were able to block cell adhesion to laminin, despite the presence of binding sites for fragment 1. A few cells had very low numbers of high affinity receptors for either fragment 1 or 8. The latter cell type was used to demonstrate that complex formation between laminin and nidogen, which binds to fragment 1 structures, reduces the potential of laminin for cell binding. 相似文献
4.
Laminin increases both levels and activity of tyrosine hydroxylase in calf adrenal chromaffin cells 总被引:8,自引:5,他引:3 下载免费PDF全文
We have investigated the effects of substrate-bound laminin on levels of enzymes of the catecholamine biosynthetic pathway in primary cultures of calf adrenal chromaffin cells. Laminin increases the levels of the enzymes tyrosine hydroxylase, dopamine-beta-hydroxylase, and phenylethanolamine-N-methyl-transferase. This effect is selective, in that levels of other enzymes (lactate dehydrogenase, aromatic amino acid decarboxylase, and acetylcholinesterase) are not increased. The effect of laminin can be blocked by antibodies directed against a fragment of the heparin-binding domain of the molecule, whereas antibodies directed against other fragments do not block the increase in tyrosine hydroxylase. Thus the laminin domain involved in enzyme regulation in chromaffin cells is apparently the same as that previously implicated in laminin's interactions with neurons to potentiate survival and stimulate neurite outgrowth (Edgar, D., R. Timpl, and H. Thoenen, 1984, EMBO (Eur. Mol. Biol. Organ.) J., 3:1463-1468). The increase in chromaffin cell tyrosine hydroxylase levels is preceded by an activation of the enzyme in which the Vmax (but not the Km) is altered. The effects of laminin appear to be developmentally regulated, since neither activation nor increased levels of tyrosine hydroxylase occur in adult adrenal chromaffin cells exposed to laminin. 相似文献
5.
Edgar T. Walters Mark T. Erickson 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1986,159(3):339-351
Noxious cutaneous stimulation of anterior sites on Aplysia californica causes withdrawal and turning followed by escape locomotion. Stimulation of anterior sites causes significantly larger turning responses than does stimulation of posterior sites, so that escape locomotion is always directed away from a site of 'attack'. Later phases of escape locomotion are often the same, regardless of the site of the triggering stimulus. The defensive secretions, ink and opaline, are directed along the anterior-posterior axis at the source of noxious stimulation. Ink and opaline ejections are directed to the front or back of the animal by characteristic responses of the siphon, mantle, and parapodia. Ink and opaline are ejected by a series of coordinated pumping movements of the mantle, gill, and parapodia that closely resemble triggered 'respiratory pumping' or 'Interneuron II' episodes (Kupfermann and Kandel 1969; Byrne and Koester 1978; Hening 1982). The directed ejection of secretions from the mantle cavity in response to noxious stimulation suggests a number of potential defensive functions for these secretions including aggressive retaliation, startle display, diversion, and alarm signalling (Edmunds 1975). Taken together, our results and others' suggest an integrated scheme for the functional organization of overt defensive behavior in Aplysia, and begin to suggest testable hypotheses about the integration of defensive responses on the cellular level in this animal. 相似文献
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Chloroplast glyceraldehyde-3-phosphate dehydrogenase (GPD, EC 1.2.1.13) was purified from leaves of Chenopodium rubrum L. Aggregated (≥ 106 ) and disaggregated (165 × 103 ) molecular weight forms were obtained by gel filtration in the presence of NAD+ and NADP+ , respectively. The disaggregated enzyme was separated into two isozymes by inverse ammonium sulphate gradient solubilization: "NADP-GPD I" was homotetrameric (subunit molecular weight 39 × 103 ); "NADP-GPD II" was heterotetrameric (subunit molecular weights 39 × 103 and 43 × 103 ). Isoelectric focusing of the isozymes, both aggregated and disaggregated, revealed two isoelectric forms in each case, at 4.3 and 7.7. Chloroplast GPD was "NADP-suppressed" in crude extracts due to partial oxidation, incubation with dithioerythritol restored full activity. 相似文献
8.
M H Bocchieri O A Batuman S P Hauptman I M Zitron J B Smith 《Journal of immunology (Baltimore, Md. : 1950)》1983,131(2):533-535
The ontogeny of IL 2-responsive cells in the thymus of CBA/J mice was examined in neonatal animals and in fetuses at 14, 16, and 18 to 20 days gestation. The thymocytes were tested for responsiveness to 2 micrograms/ml Con A, TCGF, IL 2, and co-stimulation by Con A plus TCGF or IL 2. These responses were compared with those of thymocytes of 6- to 8-wk-old CBA/J. Thymocytes (1 X 10(5)) were cultured, and the reaction was measured at maximum response (96 hr). Neonatal animals gave an unusually high response to TCGF or partially purified IL 2 alone, approximately five times greater than the adult. A low but significantly enhanced proliferation, stimulated by partially purified IL 2 alone, was observed with 14-day fetal thymocytes, even though cultures of these cells in medium alone had higher background proliferation than any other age tested. In the co-stimulator reaction, proliferation significantly above background was measured at 16 days of gestation with Con A plus TCGF. The magnitude of the co-stimulator reaction increased with age, especially between the 16th and 18th day of gestation and immediately after birth. 相似文献
9.
Aspects of the ecology and energetics of the egg sac parasites of the wolf spider Pardosa lugubris (Walckenaer) 总被引:1,自引:1,他引:0
Walter D. Edgar 《Oecologia》1971,7(2):155-163
Summary The egg sacs of the wolf spider Pardosa lugubris are parasitised by two ichneumonid wasps, namely Gelis micrurus and Hidryta sordidus. The parasites are bivoltine, the first generation parasitising the summer egg sac of P. lugubris and the second generation parasitising, and overwintering in, the autumn egg sac. Parasitised egg sacs have a characteristic appearance.The degree of egg sac parasitism was 9.8% and 6.9% for the two egg sac batches in 1965 and 2.9% and 34.8% for those of 1966. The degree of parasitism varies from area to area as does the percentage parasitism attributable to the two species.The gross growth efficiency for Hidryta from the first egg sac is 31.2% and from the second 16.2%. 3.0% in 1965 and 4.3% in 1966, of the annual yield from P. lugubris to predators and parasites, goes to the egg sac parasites. This represents reductions in recruitment of 9.1% in 1965 and 10.9% in 1966. 相似文献
10.
In the short day plant Chenopodium rubrum and the long day plant Nicotiana tabacum cv. Havana 425, adenylate kinase (EC 2.7.4.3) occurs as a family of isoforms, with at least two members localized in the chloroplast representing the main isoforms. In this work, isoforms were separated by anion exchange chromatography and relative isoform activities were compared between vegetative plants and plants induced to flowering. In both species examined, a light regime leading to floral induction resulted in a significant decrease in the activity of one chloroplast isoform. This decrease modified considerably the relative distribution of isoform activities, especially that between the two chloroplast activities. 相似文献