alpha-synuclein immunoisolation of glial inclusions from multiple system atrophy brain tissue reveals multiprotein components

Immunohistochemical studies have shown that oligodendroglial inclusions in multiple system atrophy contain alpha-synuclein, a synaptic protein also fo und in Lewy bodies in Parkinson's disease. We have now used density gradien t enrichment and an anti-alpha-synuclein immunomagnetic technique to isolat e pure and morphologically intact oligodendroglial inclusions from brain wh ite matter of patients dying with multiple system atrophy. Filamentous incl usion structures were obtained only from multiple system atrophy tissue, bu t not from normal brain tissues, or from multiple system atrophy tissue pro cessed without anti-alpha-synuclein antibody. We confirmed the purity and m orphology of isolated inclusions by electron microscopy. The inclusions com prised multiple protein bands after separation by polyacrylamide gel electr ophoresis. Immunoblotting demonstrated that these proteins included alpha-s ynuclein, alpha B-crystallin, tubulins, ubiquitin, and prominent, possibly truncated alpha-synuclein species as high-molecular-weight aggregates. Our study provides the first biochemical evidence that oligodendroglial inclusi on filaments consist of multiple protein components, suggesting that these inclusions may form as a result of multiprotein interactions with alpha-syn uclein.