Do Proteins Capable of Causing Spongiform Neurodegeneration Induce Aggresomes In Vitro and In Vivo as an Indicator of Their Neurotoxic Mechanisms? (P03.261)

Abstract

Objective: To explore the generality of aggresome formation in neurodegeneration, we investigated whether aggresomes arise in two spongiform neurodegeneration models, in which vacuolation is induced by neural stem cell (NSC) dissemination of puromycin-N-acetyltransferase (PAC) or retroviral envelope (Env) in the developing central nervous system (CNS). Background Several human neurodegenerative diseases are characterized by the presence of protein deposits called aggresomes. A previous report indicated that expression of PAC in certain cultured cells causes protein aggregation. Additionally, in vivo studies from our laboratory suggest that astrocytic expression of PAC induces a spongiosis similar to that induced by Env. The present study collates these findings to understand whether aggresomes are an indicator of protein toxicity in vitro and in vivo . Design/Methods: Aggresome markers were used to assay intracellar aggregates in HeLa and glial cells transfected/transduced with vectors containing either Env or PAC and green fluorescent protein (GFP), a cellular identification marker. In situ studies were executed by immunostaining for aggresomes in neonatal mice transplanted with NSCs disseminating PAC or Env. Pathologically refractive NSCs transduced with PAC displaying surface Env served as controls. Results: No aggresome formation was detected in response to neurotoxic protein transfection/transduction; however, these proteins did induce an unexpected down-regulation in GFP protein expression. Moreover, brains engrafted with PAC-transduced NSCs precipitated focal spongiform neurodegeneration, thereby overcoming a previous restriction noted with Env. These NSCs differentiated into oligodendrocytes suggesting that PAC influenced their in vivo fate and capacity for inducing spongiosis. Conclusions: The present studies indicate that while spongiogenic proteins do not universally induce aggresome formation, they can alter cellular physiology by influencing endogenous protein expression and modifying cellular differentiation programs that result in neuronal dysregulation. Whether these activities are broadly applicable to other neurodegenerative diseases mediated by abnormal proteins remains to be investigated. Supported by: The American Academy of Neurology. Disclosure: Dr. Das has nothing to disclose. Dr. Dunphy has nothing to disclose. Dr. Cardona has nothing to disclose. Dr. Lynch has nothing to disclose.