Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A cell-free assay to monitor receptor-mediated endocytic processes has been developed that uses biotinylated transferrin and avidin-linked beta-galactosidase as receptor-associated and fluid-phase probes, respectively (Wessling-Resnick, M., and Braell, W. A. (1990) J. Biol. Chem. 265, 690-699). The fusion of vesicles from heterologous sources can be detected in this assay: endocytic vesicles from K562 cells (a human cell line) will fuse with vesicles from Chinese hamster ovary cells. Fusion between endocytic vesicles is inhibited upon treatment with N-ethylmaleimide but can be restored by the addition of untreated cytosol from either cell type. The in vitro fusion reaction is also inhibited by the nonhydrolyzable nucleotide analogs guanosine 5'-(3-thiotriphosphate) (GTP gamma S) and adenosine 5'-(3-thiotriphosphate) (ATP gamma S). Other nonhydrolyzable guanine nucleotides are found to inhibit the in vitro reaction in the following order of potency: GTP gamma S greater than 5'-guanylyl imidodiphosphate (GTP-PNP) greater than alpha,beta-methylene GTP (GTP-PCP). The inhibitory effects of the nonhydrolyzable analogs of GTP and ATP are not additive. Moreover, excess GTP relieves the inhibition by GTP gamma S more than it relieves the inhibition by ATP gamma S, while excess ATP preferentially alleviates ATP gamma S (not GTP gamma S) inhibition. These properties suggest that the two nucleotides exert their effects at distinct points in the fusion process. Although micromolar levels of excess Ca2+ also inhibit vesicle fusion, the inhibition exerted by GTP gamma S appears to proceed via a pathway independent of the divalent cation. The GTP gamma S-sensitive step in endocytic vesicle fusion is found to occur at a mechanistic stage prior to and distinct from the N-ethylmaleimide-sensitive step of the reaction. This situation permits the accumulation of a membrane vesicle intermediate in the presence of GTP gamma S; subsequent incubation of these vesicles with cytosol and GTP restores their fusion competence. Characteristics of in vitro endocytic vesicle fusion suggest that similarities exist with steps of the fusion mechanism involved with membrane traffic events of the secretory pathway.
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PMID:Characterization of the mechanism of endocytic vesicle fusion in vitro. 212 Feb 6

It has been suggested that Purkinje cells (PC) play a role in organizing topographic relationships of several cerebellar afferent systems, including olivocerebellar fibers. This hypothesis is based on the observation that PC in the rat express biochemical heterogeneities during the presumptive period of olivocerebellar fiber ingrowth to the cerebellum. Previous studies designed to investigate the organization of murine olivocerebellar fibers during embryogenesis have suggested that interactions with PC may play a role in segregating olivocerebellar fibers after they enter the cerebellum. To determine whether PC heterogeneities are related to olivocerebellar fiber organization, transgenic mice carrying a beta-galactosidase (beta-gal) reporter gene linked to the promoter from the PC-specific gene L7/pcp-2 were used in neuroanatomical tracing experiments. Expression of the transgene mirrors endogenous L7/pcp-2 expression, which is upregulated earliest in parasagittal strips of the vermal cortex. Studies were conducted in vitro by using brainstem-cerebellar explants from embryonic day 17/18 (E17/18) and 18/19 mice. Applications of neuroanatomical tracer (horseradish peroxidase or neurobiotin) were made in either the caudal medial accessory olive (cMAO) or the rostral olive. These studies indicate that groups of olivocerebellar fibers and clusters of L7/lacZ+ and L7/lacZ-Purkinje cells respect common distribution boundaries during late embryogenesis. The strong correspondence between the distribution patterns generated by these two markers suggests that expression of L7/pcp-2 and the topographic organization of olivocerebellar (OC) fibers are not interdependent, but may be regulated by a common event or interaction, of a presently unknown nature, which occurs earlier during cerebellar development.
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PMID:Correspondence between L7-lacZ-expressing Purkinje cells and labeled olivocerebellar fibers during late embryogenesis in the mouse. 890 10

The cerebellar cortex and its sole output, the Purkinje cell, have been implicated in motor coordination, learning and cognitive functions. Therefore, the ability to generate Purkinje cell-specific mutations in physiologically relevant genes is of particular neurobiological interest. A suitable approach is the Cre/loxP strategy that allows temporally and spatially controlled gene inactivation. Here, we present the characterization of transgenic mouse strains expressing Cre recombinase controlled by the L7/pcp-2 gene. Endogenous L7/pcp-2 protein is expressed exclusively in Purkinje cells and retinal bipolar neurones. Recombination was detected by beta-galactosidase histochemistry in tissues from crosses of the L7/pcp-2:Cre transgenic lines with two different indicator strains, GtROSA26 and ACZL. Purkinje cells in all folia of the cerebellum displayed intense beta-galactosidase staining, whereas only few blue cells were observed in the retina and other parts of the CNS. Thus, these transgenic lines are potentially of great importance for genetic manipulations in cerebellar Purkinje cells.
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PMID:Cre recombinase expression in cerebellar Purkinje cells. 1110 49