The Journal of Neuroscience, October 15, 2001, 21(20):8072-8081
Long-Lasting Aberrant Tubulovesicular Membrane Inclusions
Accumulate in Developing Motoneurons after a Sublethal Excitotoxic
Insult: A Possible Model for Neuronal Pathology in Neurodegenerative
Disease
Olga
Tarabal1,
Jordi
Calderó1,
Jerònia
Lladó1,
Ronald W.
Oppenheim2, and
Josep E.
Esquerda1
1 Unitat de Neurobiologia Cellular, Departament de
Ciències Mèdiques Bàsiques, Facultat de Medicina,
Universitat de Lleida, E25198 Lleida, Catalonia, Spain, and
2 Department of Neurobiology and Anatomy and Neuroscience
Program, Wake Forest University School of Medicine, Winston-Salem,
North Carolina 27157
We have previously shown that chronic treatment of chick
embryos [from embryonic day 5 (E5) to E9] with NMDA rescues
spinal cord motoneurons (MNs) from programmed cell death. In this
situation, MNs exhibit a reduced vulnerability to acute excitotoxic
lesions and downregulate NMDA and AMPA-kainate receptors. Here, we
report that this treatment results in long-lasting sublethal structural changes in MNs. In Nissl-stained sections from the spinal cord of
NMDA-treated embryos, MNs display an area adjacent to an
eccentrically positioned nucleus in which basophilia is excluded.
Ultrastructurally, MNs accumulate tubulovesicular structures surrounded
by Golgi stacks. Thiamine pyrophosphatase but not acid phosphatase was detected inside the tubulovesicular structures, which are resistant to
disruption by brefeldin A or monensin. Immunocytochemistry reveals
changes in the content and distribution of calcitonin gene-related
peptide, the KDEL receptor, the early endosomal marker EEA1, and the recycling endosome marker Rab11, indicating
that a dysfunction in membrane trafficking and protein sorting occurs in these MNs. FM1-43, a marker of the endocytic pathway, strongly accumulates in MNs from isolated spinal cords after chronic NMDA treatment. Changes in the distribution of cystatin C and presenilin-1 and an accumulation of amyloid precursor protein and
-amyloid product were also observed in NMDA-treated MNs. None of these alterations involve an interruption of MN-target (muscle) connections, as detected by the retrograde tracing of MNs with cholera toxin B
subunit. These results demonstrate that chronic NMDA treatment induces
severe changes in the motoneuronal endomembrane system that may be
related to some neuropathological alterations described in human MN disease.
Key words:
ALS; autophagy; chick embryo; Golgi apparatus; glutamate
receptor-mediated excitotoxicity; membrane traffic; motoneuron
Copyright © 2001 Society for Neuroscience 0270-6474/01/21208072-10$05.00/0