Involvement of a membrane-bound form of glutamate dehydrogenase in the association of lysosomes to microtubules.
Abstract
A 50-kDa membrane protein corresponding to a membrane-bound isoform of glutamate dehydrogenase was proposed as a molecular species that could mediate lysosome-microtubule interactions. This protein, isolated from purified lysosome membranes, is a peripheral membrane protein with an ATP-dependent microtubule binding activity. We have produced antibodies against the purified 50-kDa protein to investigate its role in the association of lysosomes to microtubules using a cell-free reconstitution assay and cell microinjection. Pretreatment of purified lysosomes with the antibodies inhibited the association of these vesicles to microtubules. The blocking effect of antibodies was demonstrated by a differential sedimentation method and negative staining electron microscopy, allowing us to quantify the amount of microtubules interacting with lysosomes and the proportion of lysosomes bound to microtubules, respectively. Affinity-purified antibodies microinjected into intact cells altered the distribution of lysosomes that appeared less clustered in the vicinity of nuclei. The antibody-induced lysosome dispersion was assessed by quantitative videomicroscope analyses. These data show that the 50-kDa membrane protein could act, through its m...Continue Reading
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Reactive amino acid residues involved in glutamate-binding of human glutamate dehydrogenase isozymes
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