Increased Proteolytic Activity of the Granule Neurons May Contribute to Neuronal Death in the Weaver Mouse Cerebellum
| Autor: | Jerry M. Wright, Ekkhart Trenkner, Päivi Liesi, Olli Saksela, Sanna Murtomäki |
|---|---|
| Jazyk: | angličtina |
| Předmět: |
Programmed cell death
Cerebellum Neurite Immunocytochemistry Cytoplasmic Granules Tissue plasminogen activator 03 medical and health sciences Mice Mice Neurologic Mutants Plasminogen Activators 0302 clinical medicine Laminin medicine Animals Molecular Biology Cells Cultured 030304 developmental biology Membrane potential Neurons 0303 health sciences biology Cell Death Proteolytic enzymes Cell Biology Molecular biology medicine.anatomical_structure nervous system biology.protein 030217 neurology & neurosurgery medicine.drug Developmental Biology |
| Zdroj: | Developmental Biology. (2):635-648 |
| ISSN: | 0012-1606 |
| DOI: | 10.1006/dbio.1995.1108 |
| Popis: | The weaver mouse mutation is a genetic defect of unknown origin that leads to impairment of cerebellar granule neuronal migration and to neuronal cell death. We investigated laminin expression and proteolytic enzyme activity in this migration-deficient mouse mutant in vivo and in vitro to search for a molecular basis for the weaver defect. The weaver cerebellum showed a general increase in immunoreactivity for laminin, for a neurite outgrowth domain of the B2 chain of laminin, and for tissue plasminogen activator compared to the normal animals. Zymographic assays and immunocytochemistry confirmed that tissue plasminogen activator was the proteolytic enzyme synthesized in excess in the weaver mouse cerebellum in vivo. When placed in culture, the weaver granule neurons survived poorly on a laminin substratum, and failed to extend long neurites, unlike the normal cerebellar granule neurons. The cultured weaver granule neurons were proteolytically overactive and secreted excessive amounts of tissue plasminogen activator, which was likely to interfere with their neurite outgrowth potential on a laminin substratum. Indeed, the weaver granule neurons but not the normal neurons degraded laminin from their culture substratum and deposited a neurite outgrowth domain of the B2 chain of laminin onto their surfaces. Electrophysiology showed that the weaver granule neurons had poor resting membrane potentials (-38 V), whereas the normal neurons had normal resting membrane potentials of (-61 V). The resting membrane potentials of the weaver granule neurons were restored to near normal (-59 V) by a protease inhibitor, aprotinin. Aprotinin also rescued the weaver granule neurons from death on a laminin substratum and promoted their neurite outgrowth to the level of the normal animals. These results indicate that increased proteolytic activity accompanied with increased synthesis of laminin, and its B2 chain, distinguish the weaver mutation from the normal animals. These molecular changes may contribute to the impairment of granule neuronal migration and to the neuronal death, characteristic of the weaver mutation. |
| Databáze: | OpenAIRE |
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